The alcoholic and non alcoholic beverages are being used by human being since centuries back. Accompanying the increase in the variety of consumption there has been a parallel increase in the variety of alcoholic and non alcoholic beverages offered for sale. The alcoholic drinks market is broadly classified into five classes, starting from beers, wines, hard liquors, liqueurs and others. Similarly non alcoholic drinks market is broadly classified into carbonated drinks, non carbonated drinks and hot beverages. These include juices, energy drinks, carbonated drinks, tea, coffee and bottled water. The commercial success of a soft drink formulation depends upon a number of factors. A strong, well placed advertising campaign will bring the consumer to purchase the new product but, thereafter, the level of repeat sales will reflect the degree of enthusiasm with which the new drink has been received. The dramatic growth of fruit juice and non carbonated fruit beverage markets worldwide has been made possible by the development of new packs and packing systems and improvements in traditional packaging. Tropical fruits are the newest arrivals on the juice and fruit beverage market. Whisky is the portable spirit obtained by distillation of aqueous extract of an infusion of malted barley and other cereals that has been fermented. It can be considered as the product of distillation of an unhopped beer. Beer is the world most widely consumed alcoholic beverage; it is the third most popular drink overall, after water and tea. Rum is a distilled alcoholic beverage made from sugarcane by products such as molasses, or directly from sugarcane juice, by a process of fermentation and distillation. The Indian alcoholic market has been growing rapidly for the last ten years, due to the positive impact of demographic trends and expected changes like rising income levels, changing age profile, changing lifestyles and reduction in beverages prices.
Some of the fundamentals of the book are flavourings and emulsions, syrup room operation, fruit juices and comminuted bases, acids, colours, preservatives and other additives, high intensity sweeteners, packaging systems for fruit juices and non carbonated beverages, grape juice processing, processing of citrus juices, juice processing for pasteurized single strength, equipment for extraction and processing of soft and pome fruit juices, chemistry and technology of citrus juices and by products, legislation controlling production, labelling and marketing, biochemical events during brewing fermentations, outline of the whisky producing process, types of beer brewed, aroma compounds of rum and their formation, cider and perry etc.
The alcoholic and non alcoholic beverages described in this book are beer, wine, rum, whisky, cider and different types of fruit juices with packaging systems and other relevant parameters related to their manufacturing. The book will be very helpful to technocrats, new entrepreneurs, research scholars and for those who are already in to this field.
Carbonation and filling
Introduction
In any bottling or canning
operation, the filling
machine is the interface between the container and the product. For the
majority of carbonated soft drink installations, the final product does
not
exist until a point immediately prior to the filler. The processing
operation
involves combining finished syrup, treated water and carbon dioxide gas
in the
correct proportions, and normally this is carried out on a continuous
basis,
with the beverage being produced at a slightly faster rate than the
requirement
of the filler. Although there are many plants still operating on the
old method
of pre dosing the empty bottle with the requisite amount of syrup and
then
topping up with carbonated water, the modern process of pre mix
filling, where
the carbonated, finished product is transferred to the container in one
filling
operation, is now predominant. The accuracy of the syrup/water
proportioning
and the control of the degree of carbonation are vital to the
commercial
success of carbonated soft drink production. This chapter details some
of the
latest advances in the processing equipment. The filling machine is
unable to
improve the standard of the beverage and the correct function of the
processor
plays a major role in predetermining the ultimate quality of the
product and
the overall success of the filling operation.
In the last ten years filling
units have continued
to increase in complexity and price. Filling valves have been developed
in
three main areas: to encourage a streamline pattern of liquid flow into
the
container (vital to successful ambient filling) to
improve the control of fill height in the
container to adapt
to changes in
container design. The introduction of the large PET bottles (2 , 3 and, recently, 5 litre
sizes) has necessitated
the production of fillers with appropriately wide filling valve centres
to
accept these containers hence,
although
filling machines have increased in the multiplicity of filling valves,
they
have also increased in physical size owing to wider valve centres. At
the time
of writing, Krones AG of Neutrabling, West Germany, claim the largest
filler of
176 valves and in excess of 6 metres in diameter the
fastest filler would appear to be the 120 head
can filler from Holstein and Kappert GmbH of Dortmund, West Germany,
capable of
speeds over 2000 cans per minute.
The advances in filler design
have coincided with
the development of ambient filling facilities and the almost total
replacement
of glass by PET plastic in the large bottle sector. The inexorable
progress of
the latter material casts a shadow over the future of glass for
carbonated soft
drinks as PET bottles become larger and, more important, are breaking
into the
less than 1 litre range. The possible success of a returnable PET
bottle is a
fascinating scenario with its effect on bottling line composition and
design,
together with the added complications in the areas of distribution and
return.
The filling machine still
holds pride of place in
the production line the
individual handling
of containers at current outputs cannot fail to be impressive although
it is
recognised that the modern, high speed labelling machine is a tribute
to
engineering excellence in dealing with bottles, labels and adhesives at
speeds
never contemplated twenty years ago. At the filler, the formulated
product is
introduced into the prepared container, and the management of this
operation is
crucial high
outputs of large bottles
demand huge quantities of product, and flow rates of 50,000 litres per
hour through
fillers are commonplace. Inaccuracy, malfunction or human error can
have
disastrous effects on yields and operating efficiencies, and the
production
technologist must be aware of how the equipment is intended to function
so
that, in the event of failure, corrective actions may be speedily taken
before
substantial losses are incurred.
Carbonation
The artificial inclusion of a
dissolved gas in a
soft drink beverage was developed from the popularity of natural
occurring
mineral waters, which are discharged in a slightly carbonated form from
rock
formations in many of the well known spa resorts around the world. The
medicinal advantages of spa products have been panegyrised to the point
of
exaggeration and the ingestion of the dissolved carbon dioxide has
always been
considered an important part of the therapeutic process. What cannot be
denied
is that the addition of carbon dioxide makes any soft drink more
palatable and
visually attractive.
1. The nature and effects of
carbonation
Carbonation may be defined as
the impregnation of a
liquid with carbon dioxide gas (CO2). When applied to a soft drink
product, the
result is a beverage which sparkles and foams as it is dispensed and
consumed.
This escape of CO2 during consumption of the drink should complement
and
enhance the flavour, and will add an exciting tingle that stimulates
the
palate. The amount of CO 2 gas producing the carbonation effect is
usually
specified as volumes–meaning, in broad terms, the number of times the
total
volume of dissolved gas may be divided by the volume of the liquid. For
example, a 3.0 volume drink will contain CO2 to the extent of three
times the
volume of the beverage. A more accurate definition involving the
parameters of
pressure and temperature will be explained later in this chapter.
The organoleptic effects are
not the only benefits
of the CO2 content at
carbonations above
3.0 volumes the CO2 has a preserving property, the extent of which is
dependent
upon pH, sugar, initial microbial load and the nature of the micro
organisms.
This desirable attribute of carbonation should be considered as an
added bonus
and must not be a substitute for other precautions taken to ensure the
safety
and extended shelf life of a product.
Each soft drink formulation
requires a particular degree
of carbonation so that the effervescence is appropriate to the flavour
and
nature of the beverage. Fruit drinks–such as orange, bitter lemon,
etc.–should
contain low levels of carbonation whereas juice based drinks–colas,
ginger beer
and cream soda–should be in the medium to high range of CO2 content.
Mixer
drinks, so called as they are used mainly to mix with spirits, require
high
carbonations since the addition to other still (non carbonated) liquors
dilutes
the original carbonation level. Drinks in this category would be tonic
water,
ginger ale and soda water. Soda water filled into syphons contains the
maximum
degree of carbonation usually encountered in the industry. These
particular
containers rely upon internal pressure to dispense the contents and, as
the
syphon empties, this pressure is replenished from the carbon dioxide
dissolved
in the product.
In practical terms,
carbonation levels vary between
1 volume of CO2 in fruit drinks to 4.7 volumes in mixers and up to 6.0
volumes
in soda syphons. Figure 1 shows typical carbonation values for a range
of well known
drinks a degree of
latitude is indicated
since individual recipes require their particular carbonations. The
increasingly popular, large PET bottles constitute a special case not only does the CO2
gradually escape through
the permeable polymer material producing a marked reduction in the
carbonation
of the contents over a period of time, but the repeated opening and
closing of
the container for occasional consumption can result in the final 25/30%
of the
contents having an unacceptably low carbonation. This latter problem
arises
because each time the bottle is resealed, CO2 gas escapes from the
residual
product to pressurise the headspace volume and most of this gas then
escapes to
atmosphere on the next occasion the bottle is opened. These large
containers
are not really intended for intermittent consumption and to compensate
for the
future loss of carbonation, the product is carbonated to a slightly
higher
level than would be appropriate for the particular drink.
2. Properties of carbon
dioxide
Carbon dioxide is a
colourless gas with a slightly
pungent odour when
dissolved in water
the resultant carbonic acid mixture has an acidic and biting taste
which is not
unpleasant. CO2 does not support combustion and is used extensively in
fire
extinguishers. High concentrations in the atmosphere will quickly
suffocate
respiratory animals and since the gas is 1.53 times heavier than air at
70 °F,
great care must be taken when entering vessels that have contained CO2
and may
not have been sufficiently vented and purged in
these circumstances, residual CO2 will lie
in the base of the tank to trap the unwary entrant. Carbon dioxide is
usually
present in atmospheric air at a level of approximately 300 ppm by
volume and it
is dangerous to breathe atmospheres containing more than 5% by volume it has been postulated that
workers may be
safely exposed to a maximum concentration of 5000 ppm CO2 by volume for
8 hours
per day.
CO2 is one of the very few
gases suitable for
providing the effervescence in soft drinks. It is non toxic, inert,
virtually
tasteless, readily available at moderate cost and may be liquefied at
reasonable temperatures and pressures, allowing convenient bulk
transportation
and storage. The solubility of CO2 in both water and soft drink product
allows
an acceptable retention of the gas in solution at atmospheric pressure
and room
temperature, although slight agitation will promote an evolution of gas
bubbles
from the body of the drink which creates the attractive sparkling
effect.
The bulk storage of liquid
CO2 in soft drinks plants
is now commonplace all over the world pressurised
and insulated tanks holding CO2 at
20 bar. and maintained at a temperature of –17ºC by a small
refrigeration unit,
are available in various sizes from 5 to 50 tonnes in both horizontal
and
vertical modes. In order to obtain a sufficient supply of dry gas to
feed the
carbonation equipment, etc., it is necessary to utilise a suitable
vaporiser
unit which may be heated by water, steam or electricity.
Small scale production plants
still use thick walled
cylinders containing approximately 25 kg of liquid CO2 at 60 bar and
these are
usually connected in banks to allow a reasonable off take rate without
recourse
to additional heating. In the more remote areas of the world, carbon
dioxide is
still generated on site by the chemical action between an acid and a
carbonate e.g.
sulphuric acid and sodium bicarbonate:
alternatives would be the combustion of fuel oil or the extraction of
CO2 from
the flue gas of a boiler operation or similar heating facility.
3. Equilibrium pressure
In common with other gases,
carbon dioxide increases
in solubility as the liquid temperature decreases, and for every
combination of
(I) the amount of CO2 in solution and the temperature of the liquid
there is a
finite minimum pressure that is necessary to retain the gas in
solution. This
is a condition known as equilibrium where, owing to molecular movement,
the gas
leaving solution is equalled and balanced by the gas entering solution.
At
equilibrium pressure the gas/liquid mixture is just stable but any
decrease in
pressure or increase in temperature will render the mixture metastable
(or
supersaturated) in that the pressure/temperature combination is
insufficient to
keep the CO2 in solution. In this circumstance, gas will be
spontaneously
released (particularly if there is some agitation of, or irritant
applied to,
the solution) a condition known as fobbing
or foaming and
usually apparent when a bottle of carbonated product is opened to
atmospheric
pressure. The inability of a carbonated beverage to retain its full CO2
content
in solution at atmospheric pressure gives rise to the attractive
ebullience
observed during the act of pouring the drink into a glass and the
liberation of
further CO2 during the actual consumption.
Carbonated product held in a
container that is open
to the atmosphere will gradually lose carbonation as the gas is
liberated and
escapes from the liquid. In a closed container, this evolution of gas
proceeds
to fill the headspace volume and gradually increases the pressure,
quickly at
first and then more slowly as the equilibrium condition is approached.
The
actual rate of the transfer of gas from product to headspace depends
not only
on the proximity of the headspace pressure to equilibrium pressure but
also on
the temperature of the liquid, the nature of the beverage and the
extent of any
agitation or irritation imposed on the liquid. A quiescent, stable
product not
subjected to vibrations or movement may take many hours to reach
equilibrium whereas
the same product, roughly shaken,
will, take only seconds to attain the equilibrium state. The CO2 gas
leaves the
beverage and collects in the headspace volume to provide the necessary
equilibrium pressure to keep the remaining gas in solution at a slightly lower
carbonation than the
original value. This condition applies to all bottles and cans that
have been
filled with carbonated beverage and then sealed with the appropriate
closure.
4. Measurement of carbonation
Since the degree of carbonation is
such an important
factor in the formulation of a soft drink, it is imperative that a
standard
form of measurement of carbonation should be available this would allow the
production of particular
products at different times and in different locations and yet ensure
that the
carbonation of these products meets the required, agreed standard.
Previously,
it has been mentioned that carbonation may be quantified in volumes a volume of gas is
indeterminate unless the
parameters of pressure and temperature are specified and two scales are
in
current use. In the UK the term volumes Bunsen is popular where the gas
volume
is measured at atmospheric pressure (760mm of mercury) and the freezing
point
of water (32ºF or 0°C) an
alternative
scale used in the USA (and therefore followed by many franchise
bottlers
throughout the world) is volumes Ostwald, where measurement is also
carried out
at atmospheric pressure but any temperature adjustment is ignored. A
third
method, used on the European continent, measures carbonation in grams
per litre
and since one volume (Bunsen) is equivalent to 1.96 grams CO2 per
litre,
doubling the volumes of carbonation will give an acceptable
approximation of
the grams of CO2 per litre of product.
5. Carbonation determination
An obvious method of gauging
the degree of
carbonation would be to extract the total CO2 content from a known
volume of
product, adjust the gas volume to atmospheric pressure and, where
desired, mathematically
convert this volume to 0°C the
ratio of
gas volume to original beverage volume will give the figure for
carbonation.
This procedure is used in some QC
laboratories but is
usually restricted to low carbonation products as the routine is
somewhat
cumbersome.
A superior procedure (and
still used extensively in
the industry despite the introduction of later, sophisticated
techniques) makes
use of the equilibrium phenomenon described earlier. If the temperature
and
equilibrium pressure of a product are known, then there must be a fixed
carbonation level based on these two factors. From laboratory
measurements of
the maximum amounts of CO2 dissolved in water at various pressures and
temperatures and by the application of Henrys Law, a graph may be
produced of
the three way relationship between dissolved volumes, temperatures and
equilibrium pressures. Figure 2 shows the maximum volumes of CO2
(adjusted to
760 mm Hg and 0°C) which may be dissolved at various temperatures and
pressures. Fitting a pressure gauge to a container of carbonated
beverage and
shaking vigorously until the pressure stabilises will give the
equilibrium
reading having also
noted the
temperature of the product, these two readings may be applied to the
graph and
the degree of carbonation determined. For example, an equilibrium
pressure of 2
bar at a temperature of 6°C would indicate a carbonation of 4.0 volumes.
Unfortunately, this simple
procedure is prone to
inaccuracy owing to the possible inclusion of air in the beverage. (The
presence
of air in a carbonated product will radically affect the future quality
and
shelf life of the drink since the oxygen element of the air promotes
aerobic
spoilage and oxidation of certain constituents.) A further complication
is that
air is roughly one fiftieth the solubility of carbon dioxide, and
although it
may be considered that this small fraction renders the presence of any
air
inconsequential, the opposite is actually the case any
air contained in the product will exclude
approximately fifty times its own volume of CO2. In fact, air in its
normal
composition of 21% oxygen and 79% nitrogen (ignoring trace gases and
water
vapour) does not dissolve in liquids to produce dissolved oxygen and
nitrogen
in these same proportions owing
to the
differing solubilities and proportions of the two main constituents,
the
dissolved air is actually 35% oxygen plus 65% nitrogen. This enrichment
of the
oxygen proportion is unfortunate since it is this particular component
that is
responsible for many of the spoilage problems associated with air
contamination.
When measuring the
equilibrium pressure of a sample
of carbonated product, other gases (such as oxygen and nitrogen
dissolved from
atmospheric air), if present, will also exert partial pressures
dependent upon
the individual presences and solubilities. In the case of oxygen and
nitrogen,
although the proportions may be small, the solubilities are much lower
than
that of CO2 and therefore the partial pressures necessary to keep the
foreign
gases in solution will be higher. In this eventuality, the total
equilibrium
pressure (being the summation of the partial pressures of CO2, O2 and
N2) will
be greater than that produced by the carbon dioxide content alone. This
enhanced pressure, gauge reading during the carbonation test will
indicate a
higher carbonation level than is actually present. A high air content
not only
produces a false reading of the carbonation level but also imparts a
flatness
or lack of sparkle to the beverage and results in a stale flavour.
In order to avoid a
distortion in the carbonation
reading produced by dissolved oxygen and nitrogen, a simple
modification
applied to the pressure/temperature procedure previously described will
allow a
more accurate determination of the CO2 content: when the container is
shaken to
equilibrium, the first pressure is allowed to escape slowly to
atmosphere and
the container then agitated again to the equilibrium condition, which
is the
pressure used to compute the carbonation level from the graph in Figure
2. This
adaptation is often referred to as the second shake method and
eliminates the
misleading effect of any dissolved air since the latter, being less
soluble
than CO2, will leave solution during the first shake and will be vented
off as
the container is de pressurised.
The equipment used to
determine the equilibrium
pressure in a container will vary according to the supplier, but
basically
consists of a hollow piercer (or lance) which enters the bottle cap or
can lid
and is connected to a pressure gauge and a release valve. Glass bottles
should
always be enclosed in a metal cylinder during the agitating operation
but
plastic bottles and cans may be held in an open frame as shown in
Figure 3.
When a filled bottle or can
is selected for a
carbonation test it may have been obtained directly from the production
line,
or it may have been extracted from warehouse stock, or it may have been
delivered to a central laboratory from a satellite factory in the last two instances,
the containers will
have attained equilibrium pressure but bottles and cans taken from the
production line will not have reached that condition and require
special
attention before being tested. The container should be wrapped in a
cloth
dampened with cold water and shaken vigorously for at least 30 seconds
and then
allowed to rest undisturbed for another 5 minutes this
procedure will ensure that equilibrium
conditions have been obtained for all gases in the package, i.e. the
gases will
have been distributed between the headspace and the product according
to their
solubilities and presences.
The test may now proceed as
follows:
(1)
Check that the release valve
is tightly closed.
(2)
Place the bottle or can in
the apparatus and puncture the crown, cap or can base with a firm
movement to
ensure that a seal is made.
(3)
Check that the pressure gauge
has registered and record this reading for possible comparison with the
second shake
pressure.
(4)
Open the release valve
slightly and allow the top pressure to escape in a controlled manner
until the
gauge reads zero or bubbles escape from the beverage.
(5)
Firmly close the release
valve.
(6) Shake the container and tester
vigorously until the
pressure gauge rises to a maximum reading and no further shaking will
increase
it record this
pressure.
(7)
Release the pressure, remove
the container from the tester and immediately measure the temperature
of the
product taking care to do nothing
that would raise
this temperature.
(8)
Using the pressure reading
obtained in (6) and the temperature obtained in (7), determine the
carbonation
from the chart in Figure 2 where the vertical pressure line meets the
horizontal temperature line.
If the point of intersection
of these lines lies
between particular carbonation curves, it is usually satisfactory to
estimate
the actual carbonation level to
obtain
greater accuracy, the proportion of the horizontal (pressure) values
may be
used for interpolation of the exact carbonation. Instruments should be
carefully maintained and regularly checked any
inaccuracies in measuring temperatures and
pressures will obviously produce imprecision in the carbonation reading.
The
difference
between the first shake and the second shake pressures is significant.
If the
beverage is completely free of all gases except carbon dioxide and the
headspace volume is of the order of 5% of the total container capacity
(as is
usual in most bottles and cans), then the percentage fall in
equilibrium
(gauge) pressure between first and second shakes will be approximately
5% if the process
is repeated several times, the
pressure will reduce by 5% each time until all the carbonation is lost.
Taking
into account the CO2 lost between shakes and the internal volume of the
apparatus plus pressure gauge, etc., a reduction of 7 8% between first
and
second shakes could be considered acceptable results
in excess of this figure will indicate
that dissolved air is probably present and the cause should be
investigated and
rectified if reasonably air free (and oxygen free) products are to be
produced.
Effective application of quality control
Introduction
Although the organoleptic
qualities of soft drinks
and some of their major ingredients present specific problems in the
attainment
of consistent high quality, this challenge has been successfully met by
the
introduction of comprehensive quality control (QC) and quality
assurance (QA)
systems incorporating advanced laboratory and in line instrumentation
aided by
the application of statistical and microbiological techniques relevant
to
highspeed packaging operations.
The effects of increasing
legislation, added to the
growing consumer insistence on safer products and higher quality
standards in a
competitive market, have augmented the prime objective of the modern
quality
technologist the achievement of
consistent product quality
within company standards. Supportive expertise must now be provided to
reduce
manufacturing costs by tighter controls on raw material quality and
utilisation, and to improve production line efficiencies.
This chapter reviews the
evolution and growing
importance of both QC and QA in the soft drinks industry. Particular
emphasis
is accorded to the practical problems of establishing and operating
effective
quality systems in three types of business, viz. small to medium,
national and
international: not surprisingly, the wider scale of quality supervision
demanded by both national and international operations receives
principal
attention, although the particular issues relevant to smaller companies
are
also highlighted.
As production speeds increase
and equipment becomes
more complex, it is particularly important that the QA systems are
geared to
prevent defectives as distinct from the QC systems applied in plant in
order to
detect defectives.
Finally, the chapter examines
some of the important
technical factors that are likely to influence the industrys growth and
development, emphasising the contribution required from quality
technologists
both now and in the future and stressing the prospect of challenging
and
exciting careers for newcomers to the soft drinks industry.
Evolution of QC in the soft drinks industry
1. Concept of quality
Before beginning to describe
the development and
increasingly important role of QC in soft drinks manufacture, it is
important
to first lay down the ground rules for achieving consistent first class
quality, as this requires a multidisciplined approach within each
company in
order to be successful. Put simply, manufacturers produce their various
product
flavours to formulations which incorporate predetermined quality
standards
governed by consumers expectations of a consistent, good flavoured and
refreshing drink, at a reasonable price. We therefore have three
critical areas
of quality to consider.
•
Quality of design what we
believe our consumers want
•
Quality of manufacture our
best efforts at making it
•
Quality of marketing what
the consumer actually gets.
These
shall now be examined in
more detail.
Quality of design. This is an
R&D and marketing
responsibility, to quantify what the consumer wants (no mean task) and
develop
formulations that match this expectation. Raw material sourcing, costs
and
availability, compositional legislation and processing requirements all
feature
in this important development stage. As there continue to be many
notable
failures with new soft drink products, it must be assumed that this
area of
quality continues to prove most difficult to quantify accurately. QC
input at
this stage is normally limited to establishing the necessary tolerances
for the
quality parameters to be used in production control and verifying that
the
processing requirements can be met.
Quality of manufacture. The
bulk of this chapter
will be devoted to the application of QC during the manufacturing
process for
carbonated soft drinks, requiring the combined disciplines of
chemistry,
physics, engineering, statistics, microbiology and
common sense! With high volume production and using statistical
sampling
methods, the achievement of 100% product fully within specification is
not
normally possible. A more practical target is to ensure the maximum
expected
quality according to the process capability of the production line,
which
should have been selected to meet the companys quality standards.
Quality of marketing. In
addition to their role in
the development of new products (or re formulation of existing
products), the
marketing function has an important responsibility for ensuring that
their
companys product range reaches the market in the same condition as it
was when
produced. Through co ordination and liaison with sales, production and
distribution, marketing can help ensure that products reach the
consumer well
within shelf life and are competitively priced and packaged. The
effects of
age, heat, sunlight and dampness during storage before sale, the
interaction of
some ingredients plus possible microbiological activity in the product,
all
combine to reduce the factory fresh product quality. Although soft
drinks
suffer far less from these factors than many other products and have,
in most
cases, a shelf life of up to one year, products containing light or heat sensitive
ingredients such as ascorbic
acid, quinine, aspartame and certain food colours, can deteriorate
appreciably
and lose their palatability and attractive appearance. This can be a
significant problem in certain overseas markets.
These three key areas of
quality must be borne in
mind when setting up a comprehensive quality system extending from raw
material
supplies right through to final point of sale.
2.
Evolution of soft drinks QC
A
number of key factors in the
development of the industry after the Second World War helped to
accelerate the
evolution of soft drinks technology and the need for in plant QC. These
included
•
Increased demand for
international branded soft drinks particularly
colas
•
Introduction of soft drinks
legislation covering product composition, contents (volume), labeling,
ingredients and prescribed container sizes
•
Significant new product and
package developments, including the introduction of comminuted fruit
drinks,
low calorie drinks and one trip containers particularly PET bottles.
These factors brought in
train the introduction of
the pre mix filler design (where the finished product and not
carbonated water,
is handled in the filler bowl) and the coagulation chemical treatment
of the
raw water, which required more technical supervision in plant.
Although,
initially, laboratories were staffed by either qualified chemists (who
tended
to be laboratory, rather than plant, oriented) or trained production
personnel
(as in the USA), evaluation of the procedures and QC approach used by
the major
international franchisors enabled these to be selectively applied in
the
industry, demanding the employment of multi disciplined technologists
with
direct plant experience. As their contribution to the business
increased, so
did their status in the industry. The following sections review the
application, in practice, of quality systems in three different levels
of
business:
•
The small to medium business
•
The national manufacturer with
multiple plants
•
The international (franchise)
business.
The small to medium sized business
Many of these were family
owned businesses supplying
local sales and with strong brand loyalty. After many years of heavy
dependence
on experienced, reliable production personnel for quality supervision,
the need
for closer technical control of production became increasingly apparent
as
production speeds increased, formulations became more complex and one
trip
packa ging was introduced. These companies were also competing with the
high quality
branded products supplied by national companies and had to reassess
their
quality of design, manufacture and marketing to stay fully competitive.
With
increasing dependence on the new QC function and its vital contribution
in the
control of raw material utilisation and costs, QC became more firmly
established in the management team and progressively assimilated the
necessary
techniques to apply the new skills of microbiology and statistics in
their
quality plan. Where two or more plants were operated, a central QC co
ordinating
role became necessary to ensure common standards, procedures and
quality
performance, and these responsibilities were coupled with product and
packaging
development. QA systems began to be developed to prevent production of
defectives as well as further improvement in QC procedures and
equipment for
the detection of defectives.
1. Contract packing
As larger companies turned to
contracting out
production as an alternative to building new, expensive plant, this
development
became an important catalyst for smaller businesses with latent
expansion
plans. The high plant and product standards demanded by the contractors
frequently required up grading of plants, resources and, in particular,
the QC
function. Marks and Spencer have provided a good example of the growth
potential for their suppliers through contract packing in the UK provided
that the packers recognise the
critical role of quality in this type of operation.
2. Setting up a cost
effective system for QC
As close control of overheads
became increasingly
necessary in the highly competitive drinks market, there were major
constraints
in the smaller companies on the introduction and expansion of QC and
progress
was somewhat slower than in larger companies. Basic tests for Brix,
carbonation
and contents were initially introduced, but as product development
became
increasingly important, more experienced chemists were engaged to
handle both
QC and product/packaging development. This also enabled a more
professional
approach to be taken and prime attention was given to the principal
sources of
substandard quality by setting tighter Brix and carbonation standards
and by
checking these key quality parameters at regular intervals throughout
production.
Similarly, procedures for ingredient processing and accuracy were
improved
through the introduction of Brix and acidity standards and closer
laboratory
supervision of flavoured syrup preparation.
Finally, the introduction of
benzoate preserved comminuted
bases for fruit drinks, replacing juice based drinks preserved with the
more
effective sulphur dioxide, highlighted the need for more stringent
hygiene
procedures and routine microbiological control.
It is interesting to note
that until QC had proved
itself in many organisations, initial reporting relationships were to
production management and this is still the norm in many US plants
where
trained production personnel handle the QC responsibilities.
Independent
reporting to general management developed as the value of effective QC
became
more apparent.
In summary, therefore, with
limited resources
available, the operating costs of QC were more than off set by the
savings in
ingredient utilisation during processing, i.e. through less waste and
by tighter
control of the syrup/water proportioning during the pre filling
blending and
carbonating process. Reductions in line rejects and in consumer
complaints were
other areas of cost benefit through the introduction of QC.
Finally, elimination of trade spoilage
(which could affect considerable quantities of stock in the trade) was
achieved
through more frequent intensive sanitation procedures, including the
introduction of hot sanitation techniques before and after production
of the
more sensitive beverages containing comminuted fruit bases.
3. Product and packaging
innovation
Companies in this category
had a significant
advantage over larger companies in being able to launch new products or
packaging more quickly and with less investment risk. This greater
flexibility
enabled the more alert companies to capitalise on current consumer
trends with
minimum advertising spend, i.e. through local launches. Where
necessary, the
companys own technical resources could be augmented by specialist
consultancy
support and a number of examples exist of impor tant innovations to the
industry introduced in this way and adopted later by larger companies.
A major
contribution to the success of such innovations was made by the chief
chemists,
quality managers or technical managers of these smaller operations.
Some
companies
also had the good fortune (or wisdom) to have acquired natural spring
or well water
sources which could be more fully exploited with the dramatic growth in
bottled
waters.
Although the soft drinks
industrys concentration in
recent years has sadly led to the closure of many smaller businesses,
those
that have survived through shrewd marketing, contract packing, or by
becoming
low cost producers, have also contributed to the industrys
technological
development and owe this, in some measure, to the efforts of their QC
staff.
National operations with multiple plants
1. Impact of industry
concentration
The increasing concentration
of the international
beverage business, through acquisitions, joint venture and equity
share, has
significantly reduced the number of soft drinks manufacturers in Europe
and the
USA. In the UK, for example, there are less than a dozen major
carbonated drink
manufacturers operating high speed, low cost production units generally
on a multi shift basis. This has
required some adjustment in approach to the control of quality through
up dating
of test procedures, sampling plans and use of in line inspection
equipment.
Through improved plant design, both processing and filling plant have
increased
reliabilities but the sheer scale of the operation can mean major cost
penalties when things go wrong. With 1000 bottles per minute (bpm),
bottling
lines capable of producing over eight million cases of product per
annum and
canning lines now operating much faster than this, QC response to line
problems
has to be immediate, the problem rapidly assessed and remedial action
implemented without delay.
Reduction in operating plants
has, however,
eliminated some of the problems of product quality variability between
plants a
significant issue in the past in some organisations.
2. Organisation of QC at
plant level
A key requirement for plants
operating shift systems
is the achievement of equal quality performance on all shifts. This is
normally
a people related problem requiring considerable company effort in the
selection, training, motivation and supervision of key line personnel particularly
as automation reduces the number
of line operators, all of whom make some contribution towards product
quality.
Basic requirements for an effective
QC system include
•
Comprehensive raw material,
processing and finished product specifications
•
A quality plan (endorsed in a
company technical manual) identifying the sampling frequency and
source, tests
required and test equipment to be used
•
Well equipped laboratory
facilities, ideally located close to both production floor and key
processing
operations and including separate microbiological laboratory
•
A clear understanding of the QC
functions responsibilities and level of authority by both plant and
central
management
• A positive, planned programme for
the training, re training
and motivation of the QC team.
3. Centralised organisation
for quality
In a multi plant operation,
co ordination and
standardisation of quality systems are fundamental to the achievement
of
consistent quality standards. This responsibility may be vested in a
quality
controller or manager, with a small support team for statistical data
processing, development of new test procedures and a hygiene specialist
(or
microbiologist) for plant sanitation audits. Regular auditing of all
company
plants will be a key responsibility of the central quality function to
assure
senior management that quality is. indeed, under control. This is
therefore a
quality assurance responsibility, rather than one of quality control
and helps
to differentiate the respective roles within the quality organisation.
In a larger organisation, the
central quality
function may be included with engineering and R&D, and be
placed under a
technical director with full board authority. Clear functional and
reporting
responsibilities of the plant QC manager with both plant and central
management
must be defined. One favoured structure is for the QC manager to report
to the
factory manager with functional responsibility to the central quality
controller.
The central quality function
would also have
responsibility for the preparation and updating of all technical
manuals, for
liaison with both R&D and marketing in the development and
introduction of
new products, packaging and ingredients and with R&D and
engineering in the
development of new process systems.
4. Bottling versus canning
QC requirements
Although a number of routine
tests are common to
both canned and bottled products (e.g. Brix, carbonation, pH or
acidity, fill
contents and microbiological status) there are certain important
differences in
either test procedure or emphasis that need highlighting. Owing largely
to the
design and material of the modern can, higher production efficiencies
are
generally obtained on canning lines than on glass bottling lines and,
with
fewer stoppages, quality tends to be more consistent. The quality
integrity of
the can and its contents depend heavily, however, on close control of
the end seaming
operation and effective headspace air removal through flushing with CO2
or
nitrogen immediately prior to can end application. Nitrate levels in
process
water must be low as can corrosion may develop with high nitrate
content. Sugar
for canning must be free from sulphur dioxide preservative (still used
in some
parts of the world) and it is essential that any proposed change in the
design,
composition or specification of the can or end component is advised to
the
canner by the supplier and, where considered necessary, thoroughly
checked out
before adoption. This is particularly relevant to the internal
lacquering
system used and the PVC compound on the end component. Can contents are
normally checked by an in line fill height inspector which employs a
radioactive
isotope source.
In bottling operations, high
quality glass or PET
containers are vital for good line performance. While crown closure
application
is quite simple and presents few quality problems, close control of cap
application (both plastic and aluminium caps) is necessary for good
carbonation
retention yet easy consumer removal. Contents variability between
bottles can
occur with low calorie and some foaming products at the narrow neck
fill point
of the bottles, making it difficult to balance equipment settings to
provide
both good fill and standard carbonation.
Efficient utilisation of
ingredients through tight
control of fill contents and Brix (or acidity for low calorie drinks)
is a
significant QC responsibility in both canning and bottling and will
avoid major
cumulative losses on high speed units particularly. Consistent high
quality
normally means maximum raw material conversion with minimum wastage.
5. Equipment selection for
quality
In view of the major
investment involved for modern
high speed bottling and canning lines (e.g. £4 million for a 1000 bpm
returnable bottle line) the capability of the line to meet all of the
companys
quality standards must be carefully assessed before purchase. Each
equipment
component contributes to the final product and package quality, and it
is
important for QC to participate in equipment selection from the outset
through
to commissioning and final assessment of the plants process capability
against
the quality tolerances demanded by the company.
6. Development of in line
quality monitoring equipment
Following the major increase
in production speeds in
recent years, periodic on line sampling followed by laboratory testing
proved
to be inadequate as action response to substandard quality was too
slow. Development
of in line test equipment has accelerated in both Europe and the USA
and
alternative equipment is now available to monitor key parameters such
as Brix,
carbonation, pH, colour, clarity, etc. Although earlier equipment was
designed
to monitor the appropriate quality parameters, the latest designs
transmit the
test results to the process control mechanism, ensuring that any out of
standard
situation is rapidly corrected. Prime interest in Brix and carbonation
has
provided equipment available from a range of manufacturers including
Terris,
Anacon and GAC in the USA and also Maselli and Embra in Europe. Density
monitoring in line, as an alternative to Brix, is preferred by some
soft drinks
manufacturers and equipment is available from Paar Scientific Ltd,
London.
Increased popularity of diet drinks (containing no added sugar) has
required
alternative control parameters such as acidity, and in line
instrumentation
using infrared spectroscopy is now available.
In addition to the basic
tests for carbonated
products, water treatment plant control can be readily exercised by the
use of
various types of in line instrumentation for monitoring pH, total
dissolved
solids, alkalinity, residual chlorine, etc. Other well established
systems
include in line empty bottle inspection (after washing) utilising new
camera
techniques, bottle washer detergent strength monitoring by conductivity
and
fill height inspection for both bottles and cans.
Recent developments include
multiple label
inspection (an increasingly important requirement on high speed
bottling lines
as manning levels are reduced) and in line microbiological sampling
linked to
rapid test methods for evaluation of finished product stability before
release
to the trade. Clearly, this has become a major feature in the quality
control
of high speed soft drink production lines demanding familiarisation of
QC
personnel with the operating principles and techniques of this
equipment.
7. Potential quality problem
areas
The prime sources of variable
product quality in a
typical large production plant will now be examined in detail. These
problems
tend to stem from five principal sources:
•
Poor material quality
•
Process malfunction through
either equipment failure or human error
•
Ingredient omission through
either equipment failure or human error
•
Inadequate sanitation
•
Malfunction or inadequate
control of filling/carbonating/proportioning equipment.
Raw material quality. From the range
of ingredients used, chemical
additives produced to BP or equivalent standards are unlikely to
provide
quality problems and the quality plan should therefore focus on sugar,
CO2 and
fruit materials. Although these particular ingredients should be
tightly
specified and quality controlled during manufacture, they are more
likely to
provide problems in some parts of the world compared with other
ingredients.
The quality plan should, therefore, include batch sampling and at least
physical examination of the fruit materials, taste and odour checks on
CO2 and
Brix, colour, taste and micro checks on each batch of sugar. Water, as
a prime
ingredient and liable to seasonal quality variation, requires
particular QC
attention in respect of both incoming water quality and control of
treatment
used. See Section which covers this vital area in more detail.
Packaging
materials can present short, sharp, serious problems on the production
line and
inspection policies differ from one company to another. Some companies
develop
a comprehensive vendor rating scheme which includes regular inspection
visits to
suppliers plants by QC staff from the bottling or canning plant, with
free
access to the suppliers quality records. Alternatively, incoming goods
inspection schemes can be established for statistical sampling and
examination
of incoming packaging for approval (or rejection) before use. Selection
of the
best system will depend on the reliability of the supplier and
availability of
the packaging a real problem in certain
countries: In view
of the critical importance of container dimensions for good filling and
handling on the production line, spot sampling (at least) for
dimensional
checks is a worthwhile insurance before the containers are filled.
Unfortunately, in many countries, serious packaging defects continue to
be
discovered either on the production line or, worse still, in the trade,
through
lack of appreciation of the value of pre use inspection schemes.
Process malfunction. Although
a malfunction or
operator error can occur at any time in either water treatment or
flavoured
syrup preparation, morning start up (particularly Mondays or after
holiday shut
down periods) tends to be the most vulnerable period when QC needs to
be on
guard against unusual problems developing. Coagulation water treatment
plants
can be notoriously unreliable after shut down periods and when they are
subjected to peak early morning demands. In flavoured syrup
preparation, some
products require special processing such as filtration, pasteurisation
or
homogenisation which, under peak pressure conditions, can be
inadequately processed
with disastrous effects on the finished product in the trade. Each
important
stage or the ingredient processing operations has to be highlighted in
the
Quality Plan, with appropriate supervisory checks by QC staff and the
status of
the process logged for each days production.
Ingredient omission. Although
effectively part of
the previous section on process malfunction, omission of vital
ingredients
continues to be a costly vulnerable area of processing operation in
many
companies. This is recognised by the major international franchisors
who
normally supply their bottlers with a unit pack which includes all the
key
ingredients for flavoured syrup preparation except sugar, making the
syrup
process much simpler and more reliable. Where unit packs are not used,
formulae
need to be clear and unambiguous, with the ingredients added in an
optimum
sequence as certain, ingredients can
interact. Various
systems are used to verify the accurate addition of all the
ingredients,
including operators double checking each others measurement and
addition of
every ingredient and logging these in a batch report. While the
successful
application of modern laboratory techniques such as HPLC has enabled
analytical
verification of Ingredients such as saccharin, benzoate preservative
and
caffeine, other ingredients such as flavour (essence) content, fruit
juice or
comminuted fruit content, quinine, aspartame, sodium citrate, etc.,
cannot be
readily checked before the syrup is required for production.
Fortunately, more
advanced syrup or finished product blending systems are being developed
and are
already operating with apparent high reliability, including in line
monitoring
instrumentation. In most world wide plants, heavy dependence continues
on
reliable operator processing, backed up by independent QC checking. In
addition, the important organoleptic check on the flavoured syrup prior
to
bottling creates a related problem, particularly in large operations
producing
flavoured syrups on a batch basis as the considerable number of batches
produced daily places a heavy load on the sensory capacity of the QC
staff. The
industry continues therefore to seek a suitable instrumental
sniffer/taster to
deal with this problem, although development of highly reliable
processing plant is
clearly a better option. Until then,
it remains important for QC laboratories to include adequately trained,
skilled
tasters for the vital test.
Inadequate sanitation. Major
soft drinks companies
operate comprehensive plant sanitation programmes to ensure good
product shelf life
without trade spoilage. The use of fruit juices or comminuted fruit
bases, and
the growing trend away from the use of chemical preservatives, demands
the
consistent application of stringent hygiene procedures. Hot sanitation
methods
using programmed ClP systems have proved most effective employing, for
example,
1% caustic solution at 80 °C or, alternatively, an initial cold
detergent
treatment followed by hot water sterilisation at 80 0C, for 20 30 min.
In
certain equipment systems, temporary removal of refrigerant is
necessary before
the hot treatment.
Suspect areas of plant
cleaning tend to be pipeline dead
legs, pump rotor faces, filler head springs and valves, i.e. where
fruit juice
pulp can rapidly accumulate and provide a source of infection. QC
monitoring of
plant hygiene must, therefore, include periodic physical dismantling
and
inspection of plant after sanitation, followed by microbiological
swabbing. As
it is normally impracticable to hold finished product stock until micro
clearance by QC (i.e. 3 5 days after production), the recent
development of
rapid micro methods using impedance and luminescence techniques has
enabled
results to be available in 12 24 hours (depending on the degree of
contamination) and before stock is despatched to the trade.
Malfunction or inadequate
control of
filling/carbonating/proportioning equipment. This is frequently the
most common
source of variable product quality through a combination of equipment
maintenance inadequacies or poor operator control. As described
earlier, it is
important to know the process capability of the plant (which may vary
between
products) before defining the quality tolerances to be applied. The
frequency
of sampling must be determined according to output speed and expected
machine
performance and, in some companies, the line operators are made
responsible for
the startup of the plant to the necessary Brix and carbonation
standards and
for checking output quality at regular intervals. The QC checks are
therefore confirmatory
but include more comprehensive product analyses and packaging
examination.
Critical periods demanding close operator and QC attention are flavour
or
package changes and start up/shut down of plant, as errors are more
likely to
occur at these times.
Flavourings and emulsions
Flavourings
Although flavourings are
normally used in extremely
small quantities in a carbonated soft drink, their impact can make the
difference between a tasty product and one that is bland and
uninteresting. If
follows, therefore, that many flavourings are highly concentrated and
their
application dose rate must be optimised with great care.
1. Legislation
The use of flavourings is
controlled in most
countries by the Food Regulations, which should be checked very
carefully.
Flavourings are normally classified into three categories:
• Natural flavourings, in which the
components are
obtained by an appropriate physical process (including distillation and
solvent
extraction) or an enzymatic or microbiological process from material of
vegetable or animal origin, either in the raw state or after processing
for
human consumption by traditional processes of food preparation
(including
drying, torrefaction and fermentation).
•
Nature identical flavourings,
which are produced by chemical synthesis or isolated by a chemical
process, and
are chemically identical to a substance naturally present in material
of
vegetable or animal origin.
•
Artificial flavourings, which
are produced by chemical synthesis but are not chemically identical to
a
substance naturally present in material of vegetable or animal origin.
To illustrate this, consider
bitter almond oil or,
as it is commonly known, benzaldehyde. When it is extracted totally
from
almonds, it is natural. When it is produced by either the oxidation of
benzene
carbinol or by chlorinating toluene to produce dichlorotoluene and then
saponifying with lime water, it is nature identical.
In
some instances, the use of an
artificial ingredient may be preferable, because it contains no
impurities.
Analysis can be undertaken with such accuracy that traces
of undesirable components can
easily be detected. Some of
these impurities may be harmful and too costly to remove. However if
the trace
components are not harmful, the material may be used.
Although many flavourings
will contain ingredients
from two or even all three of these categories, it is normal for the
status of
a flavour to be given as that of the lowest percentage component. This
can
often mean that a flavouring that contains 99.5% of natural components
and only
0.5% artificial ones will be given the status artificial.
2.Creation
The creation of new
flavourings is a skilled job and
can only be undertaken by someone with several years experience. A
flavourist
will have a wide range of raw materials available, arranged on an organ
from
which the appropriate ingredients will be selected. A flavouring will
often
consist of over 25 individual ingredients. For example, raspberry can
be broken
down to several basic types top notes, fruity, green,
berry, background,
woody, pippy, and sweet the whole of which will
combine to give a full
round flavouring.
3. Production
The production of flavourings
can be as simple as
mixing two or three ingredients together. In most cases, however, the
use of sophisticated
and specialised equipment is necessary. Below is a brief description of
some of
the various techniques used by the flavour industry.
Distillation. A typical
example of this method uses
soft fruit. The fruit is crushed and at the point of fermentation pure
alcohol
is added. The flavour and aroma pass into the solvent. The alcoholic
solution
is then filtered and by fractionated distillation the alcohol is
recovered (for
further use) leaving the concentrated flavouring behind. This is done
under vacuum
conditions so as not to harm the delicate flavour which may be damaged
by
excessive heat.
Extraction. Probably the best
known extraction
process is in the manufacture of separation flavourings. In this
method, a
citrus oil can be washed with a mixture of solvent and water to extract
the
oxygenated (flavour containing) compounds from the insoluble terpenes.
The
resulting soluble flavouring can be boosted with other ingredients to
give the
desired finished flavouring.
Maceration. As the word
implies, this method
involves soaking the raw material. It is commonly used for citrus peel,
herbs,
such as basil and mint, or spices such as ginger or chillies. The
material is
ground and placed in a tank with solvent to extract the flavour. A
period of
time may be allowed to elapse for full extraction, and this may vary
from a few
hours to several months. Eventually, the liquid is separated by
decantation and
is filtered. The use of ultra waves can speed up this process and is
now being
used successfully on large scale production.
Carbon
dioxide extraction. Carbon
dioxide can exist as a solid, liquid or gas, and is easily isolated in
any of
these forms. At normal atmospheric temperature and pressure, the solid
form
becomes gas without passing through the liquid phase. However, when
solid
carbon dioxide is heated under pressure, the liquid form is produced.
The use
of liquid carbon dioxide is becoming increasingly important for the
extraction
of delicate natural products.
Natural products usually
contain a large number of
different chemical compounds, which, with different solvents, can be
extracted
to a greater or lesser extent depending on their solubility in that
solvent.
The use of carbon dioxide can be very important with delicate compounds
as
extractions are normally carried out at low temperatures ( 20 °C to + 20 °C) thus
ensuring that the
material is not damaged by excessive heat.
The use of materials produced
by carbon dioxide
extraction is growing, enabling the flavour industry to develop
flavourings
more true to nature than previously.
Emulsions
An emulsion can be described
as a dispersion of one
liquid in another in which it would not normally be miscible. Most
emulsions
used in carbonated soft drinks consist of two phases, which are
homogenised
under positive pressure. The following indicates some of the
ingredients used
in beverage emulsions.
Although a wide range of
materials is used to
produce these emulsions, the ingredients are normally controlled by the
Food
Regulations which specify not only the flavourings but also the
emulsifiers and
stabilisers that can be used.
The main use of emulsions in
carbonated soft drinks is as a
clouding agent. When considering the organoleptical features of a soft
drink,
the visual appearance is extremely important as the eye appeal can
often be the
determining factor in deciding which drink is actually purchased.
Syrup room operation
Introduction
It is possibly true to say
that the design of any
syrup room depends upon the desired end product. This chapter attempts
to
detail some of the equipment and materials that are necessary for a
modern
syrup room operation. In designing a syrup room, there are many
considerations
to be taken into account. These may be grouped as follows.
Hygiene related. The design
of infrastructure, tanks
and pipework must ensure sterility and safeguard the end product from
future
spoilage. The choice of detergent and type of CIP (Clean in Place)
system is
important.
Product related. To do with
the raw material, its
storage, handling and treatment, all of which affect the future quality
of the
drink.
Process related. Plant and
equipment. From the
humble origins of the syrup rooms of the 1930s and 1940s (when syrup
batches of
100 and 250 litres were commonplace and 1000 litre batches were
unusual), the
concept has evolved to the present day syrup room being considered as a
mini factory
within the main soft drinks complex clinically designed, staffed
and operated by
qualified technicians assisted by modern plant and sophisticated
instrumentation.
Present developments include
the automated and
computeri sed systems currently available, and the latest advances
where a
multiple component mixing plant prepares finished product as opposed to
the
conventional preparation of syrup. These areas, together with the
storage and
handling of raw materials, are discussed to give an appreciation of the
size,
complexity and importance of any syrup room operation.
Syrup room design
1. Wall finishes
An elaborate interior is not
necessary, but a
critical area of any syrup room is the finish on the walls as these are
constantly exposed to harsh cleaning compounds as well as the acid
components
of the product for
wall surfaces to
last, they must be impervious to this kind of treatment. With continual
use of
water and inevitable sugar deposition, these surfaces are extremely
prone to
mould growth. Ceramic tiling has generally been used but tends to be
expensive
and spray tile finishes may be used as an alternative this
finish is applied directly to masonry
blocks and consists of several layers of epoxy enamel paint covered
with a
glaze coating.
2. Floors and drainage
A surface coating capable of
resisting strong acid
and alkaline solutions is necessary unprotected
concrete surfaces offer little
resistance to these types of solutions. Quarry tiling is an excellent
surface
but, again, can be very expensive several
less costly products have now been
introduced, based on epoxy finishes that have been developed to resist
the
corrosive effects of specific compounds. Proper drainage must be
installed to
allow fast flow of waste to reduce contact time of corrosive products
on floor
areas, and drains should always be designed to allow adequate cleaning.
3. Ceilings and lighting
A concealed or dropped
ceiling system is generally used
and is supplied as lightweight panels the
surface should be resistant to the type of
products used in a syrup room since vapours are often carried upwards
and
deposits can occur. Fluorescent lighting systems are most commonly used
and
should be waterproof to reduce the effects of corrosion and prevent
ingress of
insects.
4. Heating, ventilating and
air conditioning
Environmental conditioning is
preferable but is not
installed in many factories in the UK. The advantages of these types of
systems
are:
1.
They reduce relative humidity
which, in turn, reduces condensation on equipment and piping that could
support
mould growth.
2. They reduce airborne
contamination by filtering out
dust, etc.
3.
They reduce ambient syrup
temperatures which could affect filling performance.
4.
They improve equipment
performances by permitting them to operate at cooler temperatures.
Syrup room equipment
1. Storage, mixing tanks and
systems
Tanks are used for a number
of purposes and can vary
from a small vessel for dissolving purposes to large storage tanks.
Some
factories are equipped with syrup tanks of capacities greater than
30000
litres, although many factories still use tank sizes of 5000 to 20000
litres
and consider such batches economical. The number and sizes of tanks are
determined by many factors:
•
Number of hours in a working
day
•
Line filling speed
•
Variety of products and flavour
changes
•
Filtration requirements of
syrup
•
Sterilisation requirements
between critical flavours
•
Ageing or maturation time of
syrups
•
De aeration of syrups after
mixing
Traditional syrup rooms had
tanks with open tops and
the only form of agitation was manual, often using a wooden paddle.
Modern
syrup room tanks are now designed to be fully enclosed and are fitted
with
manholes, inspection lamps, agitators, high and
low level probes and full CIP spray ball
assemblies: level indication is often by sight glass or the use of load
cells.
Mixing systems. The correct
amount of agitation in a
tank is very important the
agitation
should be smooth since violent agitation leads to aeration which is
difficult
to remove and causes problems at the filler. A comprehensive range of
mixers is
now available and can vary from propeller type mixers to high shear
mixers. The
positioning and type of mixer to be used should be carefully selected
depending
upon the size of tank and the nature and viscosity of product to be
mixed.
Mixers can be attached to the
tops of tanks or by
more permanent mountings at the bottom or side entries. Variable speed
motors can
be fitted to ensure that excessive aeration does not occur when low
levels of
syrup are mixed in large tanks. One of the major problems encountered
in mixing
syrup is the exclusion of air it
is good
practice when preparing syrup to first add water to the tank.
The agitators should not be
set in motion until they
are well covered with liquid. All ingredient pipework should be
directed to run
additions down the side of the tank instead of allowing them to splash
into the
bulk of the liquid. Some tanks have inlet points of the bottom feed
type and
these help in reducing splashing, foaming and aeration. Syrup batches
should
generally be allowed to stand to de aerate before filling to allow any
entrapped air to escape it
is usual to
allow at least one hour minimum or two hours ideally for sugar based
syrups.
High shear mixers. High shear
mixers are often
employed in the soft drinks industry to disperse stabilisers, e.g.
xantham gum
and sodium carboxymethyl cellulose these
can be very difficult to dissolve unless the correct technique is
employed. The
high shear mixer should be started in water and the powder added as
quickly as
possible the use of
a venturi to pre wet
the particles is particularly useful. The powder is sucked down into
the
disintegrating head and dispersed before the viscosity has developed.
It is
important that the powder should never be added slowly since it will
mean that
the last of the powder is added to a mix that is already of high
viscosity and
will inevitably form lumps that will be difficult to disperse.
Liquid jet mixers. These
offer an alternative to
conventional agitators and have been used successfully for the
production of
finished syrup. The system provides a homogeneous mixture with very
little
entrained air this
is due to the short
mixing time as the mixing process starts while the vessel is being
filled. The
application for liquid jet mixers is determined by the viscosity of the
liquid
to be mixed generally
these mixers can
be used where centrifugal pumps are capable of transferring the liquids
to be
circulated.
Jet mixers are normally
installed at the lowest
point possible in a tank to ensure adequate and efficient blending in
the event
of a low liquid level the
installation
of a jet mixing nozzle in the base of a mixing tank and the circulation
of
liquid is illustrated in Figure 1.
The jet of liquid flowing out
of the diffusion
nozzle at high speed generates a reduced pressure in the inlet cone of
the
diffuser which causes a liquid stream to be sucked out of the vessel
and
carried along the
diffusion jet mingles
with the drawn off liquid, increasing its velocity. The turbulence in
the
diffuser produces a homogeneous liquid mixture and the entire contents
of the
vessel are blended in a short time without creating circular movement.
2. Pipework, fittings and
connections
The majority of pipework is
stainless steel and if
suspended ceilings are used the pipework can be run above the ceiling.
All
pipework to the syrup manufacturing area should be marked or colour
coded this helps to
eliminate mistakes and promotes
safety.
Various fittings and valves
are used to connect
pipes e.g. bends,
tees and reducers sight
glasses and instrument ports and
valves for directing and regulating the
flow and the pressure.
Permanent joints are
sometimes used by welding or
expansion. Where disconnection of pipework is required the pipe
coupling is in
the form of a threaded union which has a seal or gasket in between.
Swing bends
are often used where a piping run needs to be switched from one line to
another, e.g.
connecting CIP line to the
syrup line. All pipe connections should be tightened firmly to prevent
air
being sucked into the system and to prevent leakage of syrup. Sight
glasses are
often located in the pipeline where a visual check on the ingredient is
required. Connections may be provided to allow the mounting of
measuring
instruments such as thermometers, pressure gauges, conductivity probes
(to
detect liquid). Sampling ports can be included, but it is essential
that the
sampling port does not allow contamination to occur to the ingredient.
Valves. Many designs of
valves are available for
process systems and can, vary from manual operation to air operated
types. The
choice of valve is important for a number of reasons:
•Valves
should be leaktight
against known line pressures.
•
Air valves should close on air
failure.
•
Diaphragms should be of
approved food grade material.
•
Valves should be resistant to
harsh corrosive products, should be reliable and should be designed for
minimum
maintenance.
Shut off and changeover
valves have distinct
positions. A regulating valve allows the passage or flow of liquid to
be
controlled gradually and is used for the fine control of flow and
pressure at
various points in the piping system.
Check Valves are fitted where
it is necessary to
prevent product from flowing in the wrong direction the
valve is normally kept open by the flow of
liquid in the right direction. If the pressure on the downstream side
of the
valve becomes greater than the flow pressure, the valve disc is forced
against
its seat by the back pressure and the valve is effectively closed
against
reversal of the flow.
Pressure relief valves are
used for regulating the
pressure of the product in the piping. If the pressure is too low the
spring
presses the plug against its seat when
the pressure reaches a certain level, the force of the plug overcomes
the
spring and the valve opens. Spring tension is adjusted to set the
desired
opening pressure.
3. Ingredient flow
Pipework should be designed
to prevent any pockets
occurring along the line where the product or cleaning detergent can
collect this could
lead to microbiological spoilage or
contami nation of the syrup by a detergent. It is also desirable to
ensure that
low points are designed into pipe work so that full drainage may be
obtained
via a valve at that point.
It is essential to design the
pipe sizes to give
adequate flow but ensure that mechanical bruising of the product does
not
occur. Flow resistance will occur in pipework due to friction in
straight pipe
lengths, changes in direction of flow due to bends, valves and other
fittings.
The flow resistance is expressed in terms of the column or head of
water
necessary to compensate for loss of pressure due to resistance.
Traditional syrup rooms had
tanks on a floor above
the filling lines and the pressure arising from the head of syrup was
usually
sufficient to transport it to the production line at the required flow
rate. In
modern factories, which are designed on high output, it is more
difficult to
gravity feed and so pumps are therefore used to generate the pressure
required.
The
resistance
to the flow of a liquid results in a loss of pressure and the component
is
therefore said to cause a pressure drop in the pipe. The pressure drop
is
measured in terms of head and is equivalent to the resistance of the
ingredient, the size of pressure drop being governed by the velocity of
the
flow, i.e. flow rate and size of pipe. If the velocity exceeds a
certain value
(dependent upon the nature of the liquid) then not only does the
frictional
head increase (requiring a more powerful pump) but the flow in the pipe
becomes
turbulent and disturbed, producing a possible adverse effect on the
syrup.
4. Pumps
Nowadays, with high
throughput operations, it is
necessary to convey large quantities of liquid through pipelines often
with
large numbers of bends, valves, etc.. and through pasteurisers,
homogenisers
and other associated equipment which could all possibly contribute to
pressure
drop. Pumps need to be fitted at various points in the line to convey
the
liquid and compensate for the loss of head however,
pumping agitates the product and it
is essential that the correct pump is chosen. Many different types are
available from the range of centrifugal, diaphragm, peristaltic, gear
and
positive displacement pumps.
Centrifugal pumps. These are
often used since they
can be manufactured to a sanitary design, are suitable for CIP and are
not
capable of producing accidental over pressure. A centrifugal pump
comprises an
impeller rotating in a casing, a delivery chamber and an electrical
drive.
Liquid entering the pump at the centre of the casing is carried round
by vanes.
If the liquid has to be pumped up to a tank at a higher level, the pump
discharge pressure must be sufficient to raise the liquid to that
height. This
type of head is known as a static delivery head. The pump
characteristics
supplied by a manufacturer usually relate to water the
viscosity of a product makes a difference.
When highly viscous liquids are pumped, the pressure losses in the pump
are
higher and so the energy of the product leaving the impeller will be
lower than
for water.
During pumping, liquid is
carried from one side of
the pump to the other, creating a partial vacuum in the space once
occupied by
the liquid. This space on the suction side is then refilled with more
liquid.
Cavitation on a pump can
occur when the pressure at
the suction falls below the saturation pressure of the liquid (varies
with
temperature) and dissolved oxygen comes out of solution this can be avoided by
reducing the pressure
drop on the suction line, e.g. large pipe size. fewer valves, raising
liquid
level above pump inlet, etc.
Flow
controllers are often used
to maintain a constant flow rate an
effective method of flow control is to vary the speed of the pump,
which can be
achieved mechanically, hydraulically or electrically. The centrifugal
pump can
be used to handle a wide range of liquids provided the viscosity is not
too
high the pump is
not self priming and
the suction line and pump easing should be filled with liquid before
switching
on.
Positive displacement pumps
(rotary). There are many
types of self priming positive displacement pumps. The rotary pumps
work on the
principle of two synchronised driven lobed rotors, which have a very
close
clearance but do not actually touch each other. As the rotors turn, the
volume
between the lobes at the suction port increases and the partial vacuum
created
causes liquid to enter the pump. The liquid is carried in the space
between the
lobes and the pump casing to the outlet as
the volume between the lobes is reduced,
the pressure increases and the product is discharged.
In order to prevent
excessively high pressures,
positive displacement pumps usually have some form of relief valve,
which
automatically returns some of the liquid to the inlet if the pressure
becomes
too great. Flow is normally regulated by varying the speed of the pump.
Positive displacement pumps are generally used for handling high
viscosity liquids.
5. Measurement of liquid
The
contents of tanks may be
measured using meters, dipsticks, sight glasses or load cells. The use
of load
cells is a common method for monitoring ingredients these,
however, have some disadvantages in
that all additions need to be converted to weight.
Reliable sanitary meters have
been developed for
measuring liquids. Accurate meters are the most practical method of
measuring
quantities of liquid into a tank.
Registering meters are
normally fitted with shut off
valves which automatically close at a predetermined setting, shutting
off the
flow of liquid. Meters do have an advantage in that multiple additions
may be
made simultaneously, thus saving time and often aiding mixing. In the
absence
of meters, the dipstick method of measuring liquid is reliable and has
been
widely used for many years. These are made from stainless steel and
have a
hooked end to facilitate hanging the strip from a specially marked spot
on the
side of the tank. With the use of dipsticks, each tank must be
calibrated
individually. Using an accurate meter or calibrated measure, water is
introduced into the mixing tank: the dipstick is then calibrated to
this level
and marked. The mark is checked by repeating the process several times,
being
certain to hang the dipstick from the same point each time. Once the
calibration has been accurately esta blished, the level is scribed
permanently
into the stainless steel.
A sight glass, mounted on the
side of a syrup tank
with sanitary mountings, is another means of measuring contents in a
tank. The
sight glass should be accurately calibrated and marked. Unless careful
cleaning
is employed, sight glasses can offer hiding places for contamination.
6. Filtration of ingredients
A number of ingredients in
syrup manufacture and,
indeed, in certain instances, the syrup itself require
some form of filtration, which could range from a simple mesh filter to
a more
sophisticated plate and frame or cartridge type system. Micro
filtration is
nowadays a safe and efficient method of removal of unwanted particles
and other
turbidity components. Where high carbonation mixer drinks are
concerned, it is
preferable to ensure all active centres are removed to aid good
filling: the
syrup itself can be filtered typically through a nominal 50mm cartridge
for
this purpose.
In contrast to the
conventional filter plate systems
the modern cartridge housing concept has numerous advantages.
•
Completely enclosed, sanitary
and leak free
•
Quick change out of filter
media
•
Short cleaning and sterilisation
times
Some cartridges can be
cleaned in forward flow with
hot water and significantly reduce costs by prolonging cartridge life.
Typical
cartridge systems feature a polypropylene centre core, outer cage and
end caps
and either a cotton wound cartridge or often a charged nylon membrane.
The
components are thermo welded to eliminate the use of glue or resins,
which may
impart unwanted off flavours.
Acids, colours, preservatives and other additives
Introduction
The commercial success of a
soft drink formulation
depends upon a number of factors. A strong, well placed advertising
campaign
will bring the consumer to purchase the new product but, thereafter,
the level
of repeat sales will reflect the degree of enthusiasm with which the
new drink
has been received.
Taste panelling and market
trials are also
preliminaries to a successful launch, yet continuity of sales will
ultimately
depend upon the product itself, primarily its appearance and taste, as
assessed
by the consumer, and then, perhaps, the reproducibility of quality in
both
manufacture and storage these
latter
being the major concerns of the producer and soft drinks retailer, who
must
maintain a regular turnover to survive.
It is hardly surprising that
the development of a
new drink product can take many months, while all aspects of its
appearance,
organoleptic properties and stability are tuned to requirements. In the
final
analysis, organoleptic properties are paramount, and the aroma, taste
and mouth
feel must be complementary in their contribution to the resulting
drink.
However, the immediacy of colour and its importance to the success of
the
product cannot be underestimated.
In recent years, the use of
synthesised ingredients
has frequently been under attack by the media and, as a result, market
forces
in many countries have initiated a rapid move in the direction of
natural
ingredients.
We have seen an influx of
various natural colour
extracts to the food industry which, being largely pH dependent and
light
sensitive, have found limited use in soft drinks. A few have found
acceptance,
but even so are still open to scrutiny in terms of adverse metabolic
effects.
Many have no reco mmended ADI (Acceptable Daily Intake in mg/kg body
weight)
values, while others have values allocated which are not far removed
from those
of the synthetic colours they have replaced.
Preservatives also show signs
of being phased out,
as improved methods of pasteurisation and aseptic filling are
devised. The ability of carbon
dioxide to act as a
preservative places carbonated drinks in a strong position for future
develop ment.
A typical carbonated soft
drink comprises carbonated
water, sugar, citric acid, flavouring, acidity regulators (e.g. sodium
citrate), colouring, preservative and artificial sweeteners, if used.
The
flavour component is presented against a finely tuned backcloth of the
other
ingredients, providing the right degree of sweetness, bitterness,
sourness, and
acidity (pH) to enhance drink palatability.
Acids
Following water and sugar,
the acid component is
third in terms of concentration. Its presence tends to be taken for
granted,
yet, without its contribution, the other formula components are left
lacking in
character. Because of the general tartness or sourness in taste,
acidity is
useful in modifying the sweetness of sugar. It will increase the thirst
quenching
effect of the drink by stimulating the flow of saliva in the mouth and
also,
because of a reduction in pH level, tends to act as a mild
preservative. While
the majority of soft drinks contain acids, it is the carbonated drinks
that
have the additional effect of dissolved carbon dioxide. Not officially
recognised as an acid addition, the presence of carbon dioxide under
pressure
certainly provide that extra sparkle to mouth feel, flavour and
sharpness (or
bite) to the drink, so it has been included here under the identity
given to
its soluble form.
1. Carbonic Acid
The solution of carbon
dioxide in water exploits
weakly acidic properties. Neither liquefied nor dry gaseous carbon
dioxide
affects dry blue litmus indicator paper, but if the paper is moistened
it will
provide an acid reaction in contact with the gas. There is little doubt
that in
solution some of the gas forms carbonic acid by combination with water.
Potassium and sodium
carbonates can be used in the
production of dry carbonated drink mixes, where a blend of sugars,
fruit acid
crystals, spray dried flavourings and other additives such as
stabilisers is
formulated to produce a drink which, when dissolved in water, has a
carbonation
level of about 1 1½ volumes carbon dioxide. In its more regular role,
during
the production of carbonated drinks, carbon dioxide is introduced as
part of
the bottling sequence, being dissolved under pressure before or after
dilution
of the bottling syrup with water. Measured in volumes of dissolved gas
per unit
volume of water at a specified temperature and pressure (usually
Volumes Bunsen
at 0°C and 1 atm), the average level employed is in the region of three
volumes
although extremes of perhaps one volume and six volumes are sometimes
encountered where highly specialised flavoured products are required.
2. Citric acid
This is by far the most
widely used acid in fruit flavoured
beverages. It has a light fruity character that blends well with most
fruits and,
in fact, is found as a major constituent in many of them, e.g. unripe
lemons
contain 5 8% of the acid. It is also the chief acid constituent of
currants,
cranberries, etc., and is associated with malic acid in apples,
apricots,
blueberries, cherries, gooseberries, loganberries, peaches, plums,
pears,
strawberries and raspberries, with isocitric acid in blackberries and
with
tartaric acid in grapes.
It was originally obtained
commercially from lemons,
limes or bergamots by pressing the fruit, concentrating the expressed
juice and
precipitating citric acid as its calcium salt by running in, with
constant
stirring, a slurry of chalk and water. The crude calcium citrate was
then
filtered off, filter pressed and washed prior to treatment with
sulphuric acid
to yield the free citric acid, which was then filtered from the
precipitated
calcium sulphate, and finally isolated by concentration of its solution
by
boiling, from which crystals of the monohydrate formed.
It was noted at the time of
Dr Martins Treatise on
Industrial and Manufacturing Chemistry that a known organism existed
Mucor
Piriformis (C. Wehmer, German Patent 72,957) that
could ferment sugar directly into citric acid. Owing to the low market
prices
of Sicilian lemon juice, no wide technical application of this early
enzyme
process had been made. However, citric acid is now produced by the
action of
specific enzymes upon glucose and other sugars.
Citric acid is a white
crystalline solid and can be
purchased in its powdered form or as the monohydrate. This latter state
is more
convenient in terms of storage, as it does not have a tendency to
absorb
moisture, as does the anhydrous form.
3. Tartaric acid
This acid occurs naturally in
grapes as the acid
potassium salt and, during fermentation of grape juice, will be seen to
deposit
from solution as its solubility decreases with increasing alcoholic
content of
the wine. The acid can be obtained in four forms: dextro, laevo, meso
tartaric
and the mixed isomer equilibrium, or racemic acid. Commercially it is
usually
available as the dextro tartaric acid. The acid possesses a sharper
flavour
than citric and, as such, may be used at a slightly lower rate to give
an
equivalent palate acidity. (Note that palate acidity is a purely
subjective
measurement and it is generally agreed that a number of acids may be
used at a
concen tration different to that indicated by their chemical acid
equivalent).
Tartaric acid may be isolated
from the crude deposit
of tartrates obtained from the wine fermentation process in a similar
manner to
that originally used for citric acid by leaching the deposit with
boiling HCl
solution, filtering clear and re precipita tion of the tartrates as the
calcium
salt. Further treatment with sulphuric acid is used to liberate the
acid, which
can then be purified by crystallisation.
Tartaric acid (dextro form)
exists as a white
crystalline solid mp 171 174°C. If used in beverage production, the
acid must
be perfectly pure and guaranteed for food use. It has disadvantages in
that its
salts are of a lower solubility than those of citric, particularly the
salts of
calcium and magnesium. When using hard water, it is therefore advisable
to use
citric acid to avoid unsightly deposition of insoluble tartrates.
4. Phosphoric acid
The acid is derived from
mineral and not vegetable
sources although occurring naturally in some fruits, e.g. limes,
grapes, in the
form of phosphates. It is used in some beverages as a substitute for,
or in
addition to, citric and tartaric acids, having a sharper and drier
flavour than
either of the above acids. Its taste is of flat sourness, in contrast
with the
sharp fruitiness of citric acid, and it seems to blend better with most
non fruit
drinks. In the UK, it is not allowed in drinks claiming the presence of
fruit
juices and comminuted fruits. Its main use is in cola flavoured
beverages,
where its special type of acidity complements the dry, sometimes
balsamic,
character of the cola drinks.
Pure phosphoric acid is a
colourless crystalline
solid (mp 42.35 °C) but is usually used in solution as a strong, syrupy
liquid,
miscible in water in all proportions. It is commercially available in
concentrations of 75,80 and 90%. The syrupy character is the result of
hydrogen
bonding, which occurs at concentrations greater than 50%, between the
phosphate
molecules. It is corrosive to most construction materials and rubber
lined
steel or food grade stainless steel are recommended for holding vessels.
5. Lactic acid
Sometimes used for the
acidification of beverages,
lactic acid possesses a smoother flavour than any of the foregoing
acids. It is
supplied commercially as an odourless and colourless viscous liquid and
is
obtained from the fermentation of sugars by lactic acid bacillus.
6. Acetic acid
As in the case with
phosphoric acid, under UK
legislation this acid is limited to use in non fruit juice drinks and
really
only qualifies where its vinegary character can contribute to a
suitable
flavour balance. Pure glacial acetic acid is a colourless, crystalline
solid of
mp 16 °C and is one of the strongest of the organic acids in terms of
its
dissociation constant and displacing carbonic acid from its carbonates.
7. Malic acid
This is the natural acid
found in apples and other
fruits. A crystalline white solid (mp 100°C), it is highly soluble in
water.
Being less hygroscopic than citric acid it possesses improved storage
and shelf
life properties.
Malic acid is slightly
stronger than citric in terms
of perceived palate acidity and imparts a fuller, smoother, fruity
flavour. It
is of course, first choice for apple flavoured drinks.
Unlike tartaric, its calcium
and magnesium salts are
highly soluble and the acid presents no problems in hard water areas.
8. Fumaric acid
Not permitted under UK soft
drinks legislation,
fumaric acid is widely used in other countries as an acidulant, notably
in the
US market.
In terms of equivalent palate
acidity it can be used
at a lower rate than citric acid and typical replacement can be
employed at two
parts fumaric per three parts citric in water, sugar water and
carbonated sugar
water. Its main drawback is a reduced solubility compared with the
citric acid
and special methods need to be employed in getting it into solution.
9. Ascorbic acid
This acid (known as Vitamin
C) is not only used as a
contributory acidulant but rather as a stabiliser within the soft
drinks system
and its anti oxidant properties improve the shelf life stability of the
flavour
component in many cases.
Many of the ingredients used
in flavourings are
susceptible to oxidation, particularly the aldehydes, ketones and keto
esters.
Ascorbic acid shields these from attack by itself becoming
preferentially
oxidised and lost, leaving the flavour component unaffected. It should
be
noted, however, that while a browning inhibitor in unprocessed fruit
juices,
the effect can later be reversed should the juice be subsequently heat
treated
(pasteu rised) when the ascorbic acid present can itself initiate a
chemical
browning reaction. Another disadvantage of ascorbic acid is its effect
upon
some colours in the presence of light.
Colours
The sensory perception of
colour will influence the
tasters reception of the drink. It has been generally demonstrated that
the
colour can far outweigh the flavour in the impression made upon the
consumer.
Both quality and quantity of colour are of importance and certain
colours
provoke, or perhaps complement, a particular taste. Reds will favour
the
fruitiness of soft drinks, e.g. blackcurrant, raspberry, strawberry,
etc.
Orange and yellow tend towards the citrus flavours. Greens and blues
reflect
the character of peppermints, spearmint and cool flavours, some times
herb like
and balsamic and the browns align with the heavier flavours, e.g.
colas,
shandies, dandelion and burdock.
There is little doubt that in
the early years many
questionable practices were involved in beverage production and there
is an
interesting reference in Skuses Complete Confectioner A
Practical Guide to the Art of Sugar Boiling in all its Branches. This
book,
published c. 1890, contained information on cordials and other
beverages and,
under its section on flavours and colours, the author felt it necessary
to
point out the dangers of using certain colours such as sulphate of
arsenic,
iodide of lead, sulphate of mercury, carbonate or sulphate of copper
and
seriously admonished the used of chrome yellow (lead chromate) by
certain
confectioners who were partial to using a little chrome yellow for
stripes in
sweets. Such colours were officially banned from food use in 1925.
Today, the use of food
colouring is carefully
controlled under various legislations, with an ongoing programme of
toxico logical
studies where there is suspicion of harmful or allergic effects.
Both the EEC (European
Economic Community) and the
FDA (Food and Drug Administration of the USA) have published permitted
lists
that are under regular review. Most concern has been expressed over the
azo
colours as certain people can demonstrate an allergic reaction to some
of them.
Toxicological and allergic reactions have been reported most frequently
with
Sunset Yellow (E 110) and Tartrazine (yellow) E 162.
It has been found by
experience that a number of
food colours give a broadly satisfactory performance in soft drinks and
carbonated beverages.
The colour properties can be
affected by a number of
soft drink ingredients and good storage stability is required in the
presence
of acids, flavouring compounds and, where necessary, the preservative.
The
colour component must also be stable in the presence of light. It is
well known
that the combination of ascorbic acid and light has a detrimental
effect on
many colours. While it can be said that the colours permitted for soft
drinks
have a reasonably good all round performance, there is no substitute
for
storage trials in new product development to ascertain the real
behaviour in
the finished beverage.
The colours most commonly
encountered in the soft
drinks industry are Tartrazine, Sunset Yellow FCF, Carmoisine, Green S,
Chocolate Brown HT, the caramels and the nature identical carotenes.
Amaranth, previously widely
used, has lost ground
since its exclusion from the US permitted list by the FDA of America in
January
1976. Although Amaranth (El23) is still permitted in Europe, there has
been a
tendency towards the use of Carmoisine instead. Tartrazine and Sunset
Yellow
are being replaced more frequently by Quinoline Yellow, the slight
differences
in colour tone being compensated for in terms of intensity by altering
dosage
rates.
The consumer, also being
remarkably tolerant, tends
to demonstrate the fact that, unless one can make immediate comparisons
and
batches of beverages using different colour types are not presented
side by
side then the changeover to a new
colour will have
little effect on sales. In recent years there, has also been an
increase in the
usage of natural colour extracts within the regulatory lists. Curcumin,
carotenoids, (caramel) flavenoids, anthocyanins and chlorophyll have
all been
produced where necessary in water soluble forms (emulsions, salts,
etc.) with
varying success.
During the eighteenth century
there was little need
for rigid laws controlling additives in food or drinks. Until the
Industrial
Revolution, food had been produced in Britain for the immediate needs
of the
local communities, and trade was restricted likewise to the immediate
area.
Producer and consumer were often neighbours with a high level of trust
between
them. However, the result of the new industrialisation changed all that.
Between 1834 and 1856 it was
discovered that
aniline, produced from coal tar (a by product of coal gas manufacture),
could,
in conjunction with other agents, provide a wide range of vivid and
fast
colours. The patent taken out by a young chemist, William Henry Perkin,
for a
mauve colour produced from aniline, opened the door to a succession of
new dye stuffs
from coal tar products. These transformed the textile industry which
had
hitherto relied upon natural colouring extracts. Low cost and bright
hues
ousted the use of natural colours and had a marked effect upon world
trade. In
1868, alizarin, the colouring principal of the madder root (Rhubia
tinctoria),
was prepared synthetically and, during the same period, natural indigo
was also
being displaced in commerce by the artificial version.
Textile manufacture was not
the only use to which
the new products were directed and a selection of them soon became
available
for food use. often with dire results to the consumer.
In 1925 the compounds of
arsenic, antimony, cadmium,
etc. (referred to earlier), were finally officially banned from use as
legislation
began to take hold. Even so, it appears that little was done until the
early
1950s to regulate the use of food colours other than to ban from use
those
colours that had become obviously unsuitable for consumption, usually
at the
behest of interested parties following the outbreak of poisoning owing
to
excessive use of a particular additive. In 1954, a list of acceptable
food
colours was drawn up (hitherto only negative lists had been available)
and
subsequently, in 1957 and 1973, the list as we know it today was drawn
up of
both natural and synthetic colours.
In line with greater concern
over the food we
consume, there is a greater regard to the toxicological effects of food
additives in general and accordingly, not only do we consider the
suitability
but also the Acceptable Daily Intake (ADI). This is expressed in
milligrams per
kilograms of body weight as the amount of food additive that can be
taken daily
in the diet, without risk.
Within the EEC, the
allocation of ADI values is the
responsibility of JECFA (the Joint Expert Committee on Food Additives),
which
comprises experts representing the World Health Organisation (Geneva)
and the
Food and Agricultural Organisation of the United Nations, (often
referred to as
WHO/FAO).
Control of food additives in
the USA comes under the
auspices of the FDA. who have devised a permitted list of additives.
The EEC
and FDA lists, while subjected to a similar degree of toxicological
testing,
may differ in content. For instance, Amaranth, permitted by the EEC
list, was
de listed by the FDA in 1976.
The subject is controversial
and it is often
difficult to identify the actual number of persons showing the allergic
reaction, as the offending substance may only show adverse effects when
in
combination with a food or beverage to which the person is also
allergic. The
major deterrent is the list of ingredients on the label, which enables
those
who are allergic to identify the substance and avoid intake.
High intensity sweeteners
Introduction
The low calorie/sugar free
soft drinks market and
therefore, the use of intense sweeteners has grown dramatically in many
world
markets over the last five years. The major reasons for growth are:
(1) Sweetener development: that is,
improvement in the
taste quality of high intensity sweeteners permitted for use in soft
drinks and
consequently more acceptable low calorie/sugar free products.
(2) An increase in consumer
awareness of nutrition and healthy
eating, making the reduction of sugar intake in the diet desirable for
the
majority of developed societies.
Saccharin was the first high
intensity sweetener to
be marketed, and its usage increased during the First World War owing
to
a:sugar scarcity. Cyclamate entered the UK market during the 1960s and
was
later controversially banned in many countries as a potential
carcinogen.
The 1970 cyclamate ban
brought to an end the use of
saccharin cyclamate blends in many soft drinks markets. Soft drinks
sweetened
only with saccharin did not deliver the sweetness taste quality of the
blend
and this highlighted the need for alternative high intensity sweeteners.
It was a further 11 years
before other high intensity
sweeteners (aspartame, acesulfame K and thaumatin) gained approval for
use in
foods in major world markets.
Use of intense sweeteners
Use of sweeteners in soft
drinks is not restricted
to low calorie or dietetic products. In some countries, particularly
where
sugar prices are comparatively high, intense sweeteners are used in
combination
with sugar or glucose syrups to give more cost effective formulations.
Intense sweeteners provide
sweetness, the amount
supplied i.e. the
relative sweetness of
all intense sweeteners will depend on application.
The values quoted
in this chapter are only a guide and demonstrate the wide range of
values obtainable
under different conditions.
Intense sweeteners do not
supply the mouth feel of
sugar and, in some cases, they may supply undesirable side tastes or
prove to
be incompatible with some flavours. For these reasons, use of intense
sweeteners in soft drinks is rarely a case of direct substitution of
sucrose in
the regular product formulation: more often than not, total
reformulation is
necessary. It may be necessary to adjust the acidity and use buffers to
assist
stability of some sweeteners. Some adjustment of the flavour system
used is
commonly required and the use of gums or small amounts of sugars can
improve
mouth feel and control fobbing during filling. Use of ingredients that
mask
undesirable side tastes may also be required. Increasing the
carbonation of low
calorie products may also help mask undesirable side tastes and give
the
illusion of better mouth feel.
Sweetness synergy occurs with
many combinations of
intense land bulk sweeteners. The effects can be twofold: a higher
perceived
sweetness than would be expected from the theoretical sum of the
relative
sweetness values of the individual sweeteners used and, in some cases,
a marked
improvement in taste quality of sweeteners that have undesirable side
tastes.
The optimum sweetener system
will vary depending on
the product and will not necessarily be a sweetener blend. However, if
a
sweetener blend is to be used, a useful starting point often quoted for
blends
of two intense sweeteners is that sweeteners are used in an inverse
ratio to
their relative sweetness (to each other), so that each sweetener
contributes
50% of the total sweetness. For example, if sweetener A is half as
sweet as
sweetener B. the sweetener blend would contain twice the amount of
sweetener A
than sweetener B.
Optimum sweetener blends for
three or more
sweeteners are not predictable and should be determined by sensory
evaluation.
Several intense sweeteners
are now approved for use
in soft drinks. Four compounds acesulfame K, aspartame,
cyclamate and
saccharin have major importance in the
soft drinks
market. This chapter will give a brief review of these, together with
three
other compounds (stevioside, thaumatin and neohesperidin
dihydrochalcone) that
have limited world wide approval for use in soft drinks and two other
new intense
sweeteners alitame and sucralose currently
seeking approval.
Current sweeteners
1. Acesulfame K
Acesulfame K is the generic
name for the potassium
salt of 6 methyl l,2,3 oxathiazine 4(3H) one 2,2,dioxide it is a derivative of
acetoacetic acid and was
discovered by the German company Hoechst AG in 1967. Acesulfame K is a
white,
non hygroscopic crystalline substance at
room tempera ture solubility is good (270 g/l) in water, poor in
organic
solvents, but increases in solvent water mixtures.
Application in soft drinks,
(a) Sensory: As with all
intense sweeteners, sweetness potency of acesulfame K. relative to
sucrose
decreases with increasing concentration and varies with the medium in
which the
sweetener is being tested and the method used for quantifying sweetness.
Values for acesulfame K vary
from 110 to 200 at 10%
and 3% sucrose equivalence, respectively. The taste profile of
acesulfame K is
generally considered to be superior to saccharin. It has a rapid onset
time but
the sweetness quality is marred by a bitter astringent aftertaste that
is
particularly noticeable at higher concentrations. Sweetness quality can
be
greatly improved by combining with other intense and bulk sweeteners.
High
levels of synergism (30% and above) reportedly occur with aspartame
and, to a
lesser extent, with cyclamate, glucose, fructose and sucrose. Very
little
synergy is reported to occur with saccharin, possibly because they
compete for
the same sweet receptor site. The aftertaste of acesulfame K can be
masked in some
cases by the addition of sugar alcohols, maltol and ethyl maltol.
In soft drinks as a sole
sweetener, levels of 600 800
and 550 750 mg/1 for cola and citrus flavoured drinks, respectively,
are
appropriate. Blending with other sweeteners, in particular aspartame,
gives a
much more acceptable product. In 50:50 combinations with aspartame,
taking into
account synergy, levels of 160 170 and 140 150mg/1, respectively, for
cola and
citrus flavoured beverages would be appropriate.
(b) Stability: Stability of
acesulfame K is very
good and concentrated stock solutions can be stored and used. In
solution, no
detectable decomposition occurs at pH 3 at room temperature. Very
limited
decomposition occurs below pH 3 over extended storage periods.
Heat stability is also good.
No detectable
decomposition occurs during pasteurisation or UHT treatments.
In general, acesulfame K
appears to be non reactive
with other soft drinks ingredients. However, inclusion of acesulfame K
adds
potassium ions to the beverage and this should be taken into account
when
selecting clouding agents and stabilisers.
(c) Analysis: Qualitative
analysis may be performed
using thin layer chromatography. HPLC is the main method available for
quantitative analysis owing to the low volatility of acesulfame K,
detection
being in the UV range. Methods using isotachophoretic techniques can be
used to
determine acesulfame K, saccharin and cyclamate simultaneously.
Metabolism. Acesulfame K is
not metabolised and is
excreted unchanged from the body primarily in the urine. It, therefore,
has a
caloric value of zero. Very few micro organisms have been found to
metabolise
acesulfame K, indicating that it is also non cariogenic.
Regulation. A large number of
toxicological studies
were submitted to the regulatory authorities in order to gain approval
for
acesulfame K. The toxicity of acetoacetamide (the decompo sition
product of
acesulfame K formed under certain conditions) was also studied and they
indicated that both products were non toxic. The ADI (Acceptable Daily
Intake)
assigned by JECFA (Joint FAO/WHO Expert Committee on Food Additives)
and the
FDA (Food & Drug Administration) are 0 9 and 0 15 mg/kg body
weight,
respectively.
The UK was the first country
to approve use of
acesulfame K in food and drink with Group A classification in I983. The
FDA
gave approval for use in dry mix beverages in 1988. It is approved for
use in
soft drinks in over 15 countries, with several petitions pending.
Marketing. Acesulfame K is
marketed under the brand
name Sunett. Legislative constraints, limited production capacity and
competition from aspartame, which has better taste qualities, have
hindered the
development of acesulfame K in the soft drinks market. With capacity
problems
now overcome and more approvals in different world markets, use of
acesulfame K
should increase, particularly in areas where aspartame cannot be used.
Combination with other sweeteners will take advantage of the improved
taste
quality and apparent synergism and also assist in keeping within the
ADI.
2. Aspartame
Aspartame is the generic name
for N alpha aspartyl L
phenylalanine methyl ester. It was discovered as a potential high
intensity
sweetener in 1965 by J. Schlatter in the G.D. Searle laboratories.
Aspartame is a white
crystalline powder. Solubility in
water is 1.0 g/l at 20 °C and this is adequate for most food
applications.
Solubility increases in acid conditions and with increasing
temperatures
allowing stock solutions to be made up however, these solutions
should be freshly
prepared each day. Aspartame is sparingly soluble in solvents and
insoluble in
oil.
Application in soft drinks
(a) Sensory: Of all the
intense sweeteners currently available
for use, aspartame has a very similar taste profile to sucrose and this
has
been the overriding factor contributing to its success in the market
place.
Relative sweetness values
quoted at 4 5% sucrose
equiva lence in water are in the range 120 215. A relative sweetness
value of
180 at 10% sucrose equivalence is often used in soft drink
formulations. Taste quality
of aspartame is a clean sweet taste without the bitter metallic or
licorice
aftertaste often asso ciated with intense sweeteners some
individuals do, however, notice a slight lingering of the sweet taste.
It is
synergistic with several other intense sweeteners including saccharin,
cyclamates, stevioside, acesulfame K1 and sugars. Flavour enhancement,
particularly with fruit flavours, occurs most
notably with natural flavours.
As the sole sweetener, use
levels of approximately
500 600 and 400 600 mg/l are appropriate for cola and lemonade
beverages,
respectively.
(b) Stability: As would be
expected from a compound
essentially made up of two amino acids, aspartame undergoes degradation
in
solution. Hydrolysis of the ester bond gives the dipeptide aspartyl L
phenylalanine
with the elimination of methanol. At pH 5 and above, the main
degradation
product is formed by cyclisation to the diketopiperazine (DKP) with the
elimination of methanol. DKP may then hydrolyse to the dipeptide which
may in
turn, hydrolyse to its constituent amino acids, aspartic acid and
phenylalanine.
The critical factors that
dictate the rate of
aspartame degradation in soft drinks are pH, temperature, moisture and
time.
Fortunately, for the soft drinks manufacturer, the optimum pH range for
aspartame stability is pH 3 to 5 with maximum stability at pH 4.3.
The effect of UHT aseptic
processes on soft drinks
containing aspartame is minimal. Typical aspartame losses would be in
the range
0.5 5% for most standard treatments. Therefore, the effect of
temperature on
stability of aspartame in soft drinks is likely to be a function of
storage and
distribution temperature.
Stability of aspartame in
concentrates and post
mix/fountain syrups is generally lower than in the corresponding ready
to drink
product due to the lower pH of concentrates.
There is no direct
relationship between the
acceptability of an aspartame sweetened product, its perceived
sweetness and
the actual loss of aspartame. As the concentration of aspartame
decreases, the
relative sweetness increases, thereby partially compensating for the
degradation of the sweetener. Sensory evaluation has indicated up to
40% loss
of aspartame before the soft drink is judged unacceptable.
In dry form, when stored
correctly, aspartame is stable
for several years, making it an ideal sweetener for powdered soft
drinks.
The improved stability of
aspartame has been the
subject of several patents most of which involve co
drying with various
acidulants and or bulking agents or encapsulation, and are not
applicable to
liquid systems. However, combinations of aspartame with caramel have
been
reported to give improved stability and are the subject of one patent
application.
(c) Analysis: Qualitative and
quantitative
spectrophotometric analyses can be performed by traditional amino acid
detection methods based on the reaction with ninhydrin. Quantitative
analysis
may also be effected by HPLC. Some chromatographic methods allow for
the
simultaneous analysis of other soft drinks constituents. A non
chromatographic
method based on a non aqueous perchloric acid titration may also be
used.
Metabolism. Unlike many other
intense sweeteners,
aspartame is metabolised by the body. It is hydrolysed into the two
constituent
amino acids and methanol in the gut. These breakdown products are
metabolised
in the same way as aspartic acid, phenylalanine and methanol from other
foods.
The aspartame molecule adds nothing new to the food chain.
People with the rare human
genetic disease
Phenylketonuria have a deficiency in their ability to metabolise
phenylalanine
and their intake of this essential amino acid must be very strictly
controlled
from birth to adulthood. Therefore, they must include the phenylalanine
content
of aspartame in their dietary calculations.
Aspartame is non cariogenic
and has a calorific
value of approximately 4 cal/g.
Regulation. The PDA issued
approval for the limited
use of aspartame in foods and beverages on 24 July 1974. G.D. Searle
voluntarily withdrew it from the market shortly afterwards when
questions were
raised about the validity of some of the toxicological data used to
establish
its safety. A stay of effective ness of the aspartame regulation was
published
in the Federal Register of December 1975.
Further toxicological studies
and re evaluation of
the original toxicology data satisfied the PDA that aspartame was a
completely
safe food ingredient, and in 1981 it gave approval for use in limited
food
applications. JECFA gave aspartame a comparatively high ADI of 40 mg/kg
body
weights. The FDA ADI is 50 mg/kg body weights.
Carbohydrate sugars
Introduction
Carbohydrate sugars
considered in this chapter are
those based on sucrose derived from sugar beet and sugar cane and those
derived
from starch, e.g. glucose syrups in their various forms.
History
It would appear that the
association between sugars
and carbonated soft drinks first occurred in the seventeenth century
when lemon
juices containing naturally present sugars were added to spring waters.
Sugar
was also used during the travels of Captain Cook as an addition to
lemon juice
in order to preserve the juice for long periods. From these origins,
the use of
sugar to improve preservation and to improve the taste acceptability
has
rapidly increased. In the UK the soft drinks trade sector is the
largest market
for carbohydrate sugars, representing in 1986 87 approximately 21% of
the total
market. The amount of carbohydrate sugars used in 1986 was
approximately 210000
tonnes, the majority of which was in the form of sucrose based
products. Future
usage of carbohydrate sugars is expected to increase to approximately
292000
tonnes in 1995, even though the percentage share of low calorie
carbonated soft
drinks, which are entirely artificially sweetened, is expected to reach
approximately 18% by the same year. Because of the present European
quota
arrangements for sucrose and high fructose glucose syrup, the relative
percentage share of these products as used in UK produced carbonated
soft
drinks is not expected to alter dramatically. By comparison, a dramatic
swing
to the use of high fructose glucose syrup has occurred in the United
States and
certain South American countries for reasons of pricing.
Carbohydrate sugars
Carbohydrate sugars used in
carbonated soft drinks
can be divided into those in a dry, granular form (e.g. granulated
sugar
(sucrose)) and those in a liquid or syrup form (e.g. liquid sugar which
is a solution of sucrose in water–and glucose type syrup produced from
maize)
or, in certain circumstances, wheat (e.g. glucose syrup or high
fructose
glucose syrup).
In the UK, a type of
granulated sugar is available
(mineral water sugar) which, by virtue of its name, could be viewed as
the
sugar used for production of mineral waters or soft drinks. Although
this sugar
type is eminently suitable for the preparation of carbonated beverages,
its
name and indicated use are historical and relate to past times when the
quality
of standard granulated was deemed unsatisfactory. Nowadays, standard
granulated
from both beet and cane is of a substantially higher quality and
therefore
adequate for the production of carbonated beverages. Mineral water
sugar, which
has undergone additional purification stages to reduce the already
minute
levels of impurities present, is now used for specific pharmaceutical
and
crystallization processes.
1. Granulated sugar
Granulated sugar is a dry,
crystallized disaccharide
extracted from sugar beet and sugar cane called sucrose: commercially,
however,
it is referred to by numerous names standard granulated sugar,
dry sugar or
granulated sugar. In Europe and the USA, the quality of granulated
sugar is
independent of source, being an extremely high purity organic product.
However,
in some less developed countries the quality of sugar is such that
further
purification is undertaken by the end user. This normally takes the
form of
filtration and carbon treatment of a prepared aqueous solution.
Packaging. Granulated sugar
is supplied in various
weight packages, including sacks (25 and 50kg), 1 tonne flexible
containers and
bulk tankers. The choice of supply depends on the availability and
distribution
systems in operation in the country concerned.
When a total choice exists,
bulk tanker deliveries
are most widely received owing to their advantages over sacked
products. These
advantages are related to convenience of handling, reduced storage
space,
reduced labour cost and a decrease in sugar contamination and loss,
associated
with sack opening and emptying. For those locations that require the
convenience of bulk deliveries but do not wish to incur the necessary
cost of
installing bulk tanker reception facilities, 1 tonne flexible
containers
provide a useful compromise.
Depending on the country, the
price of dry sugars,
in particular bulk granulated sugar, can be below the price of an
equivalent
quantity of sugar in commercially available liquid form (i.e. 67% w/w
aqueous
solution). This price differential can be sufficiently great to be cost
effective for soft drinks manufacturers who currently receive liquid
sugar to
change to dry sugar and dissolve on their own premises.
Manufacture. After extracting
the sucrose from
either sugar beet or sugar cane, the juices so produced containing both
sugars
and non sugars are subjected to a series of purification steps, which
remove
the non sugars and progressively concentrate the sucrose solution.
These
processes involve precipitation and absorption stages coupled with
numerous
filtration and evaporation systems. The final purification step
involves
crystallization of the pure sucrose crystals in vacuum pans. The
resulting
mixture of sugar crystals and syrup, known as masse cuite, is
transferred to
centrifugal machines where the syrup is spun off and the remaining thin
surface
film adhering to the sugar crystals is removed by washing with water.
The damp
sugar crystals are then dried to a moisture content of about 0.02% w/w
using a
hot air granulator before being cooled and stored in temperature and humidity controlled
sugar silos.
The produced granulated sugar
is not screened to a
particular particle size distribution the
range of crystal sizes is close to the
Gaussian or Normal Distribution pattern of spread, and is controlled
during the
vacuum pan crystallization stage by skilled operators. However, to
remove any
over large lumps due to agglomeration of sugar crystals, a coarse sieve
is
normally incorporated in the system conveying sugar to and from the
storage
silos. In addition, a comprehensive system of magnets is employed to
protect
the final product from chance contamination.
2. Liquid Sugar
In the UK, commercially
available liquid sugar
comprises an aqueous solution of sucrose at a saturated concentration
of 67%
w/w (67. Brix) at 200C.
Type of delivery. Although
available in drum form
from some manufacturers, the majority of soft drinks manufacturers
receive
their supplies by specially designed bulk road tankers capable of
transporting
up to 3000 gallons of liquid sugar.
Normally, liquid sugar is
delivered at a temperature
within the range 45 60ºC when its viscosity is 48.4 and 23.9 Centipoise
(cP),
respectively. However, it is possible, for soft drinks manufacturers to
receive
deliveries that have been cooled to a maximum temperature of 30 °C if
higher
temperatures would cause problems during their filling operations. Even
at this
temperature the liquid sugar remains relatively free flowing, having a
viscosity of about 114cP (at 30ºC).
Manufacture. Certain types of
liquid sugar are
produced without undertaking a sugar crystallization stage. These
“drawn off”
syrups from the manufacturing process are, however, of a colour and
flavour
unsuitable, without further treatment, for most soft drinks
manufacturers.
Because of the high quality
requirement of the soft
drinks industry, liquid sugar supplies are normally produced by
dissolving high
quality granulated sugar in water. This dissolution process is carried
out at
an elevated temperature to reduce the level of any microflora that may
be
present. The produced syrup is then normally filtered through a filter
aid
based system. Carbon filtration and de ionisation, using resin columns,
are
incorporated by some manufacturers in the liquid sugar production unit
if the
quality of the granulated sugar is insufficient to produce the
necessary
standard of liquid product.
Treatment of the liquid sugar
with ultraviolet
radiation is generally undertaken to minimize further the presence of
any
microorganisms. This is carried out using an in line system whereby the
liquid
sugar passes through a number of narrow annuli, which ensures a short
path
length for the ultraviolet radiation to pass, which is necessary for
high
absorbing liquids.
Temperature adjustment is
then carried out, if
necessary, by plate heat exchangers before final filtration as the
liquid sugar
is loaded into despatch tankers.
3. Glucose syrup: high
fructose syrup
Glucose syrups and high
fructose syrups can be used
as a complete, but more usually partial, replacement of sucrose in the
majority
of carbonated soft drinks. Used in conjunction with sucrose, syrups
with
appropriate fructose contents enable sweetness levels to be adjusted
according
to specific market preferences.
Complete sucrose replacement
in carbonated soft
drinks has occurred in certain non European countries with 55% fructose
syrup.
However, this is not the case within Europe since high fructose syrup
production is governed by the EEC quota system.
Glucose syrups of various
types are used exclusively
in certain health type soft drinks.
Type of delivery. Glucose
syrups, although available
in drum containers, are generally supplied in specially designed road
tankers.
The syrups normally incorporated are: dematerialized 95 DE (dextrose
equivalent, see Manufacture below) syrup 63DE
syrup high fructose
syrup of 42% fructose and
various blends of the above, with and
without sucrose to produce the required level of sweetness, viscosity
and mouth
feel.
The temperature of delivered
glucose syrup depends
on the specific type involved. 95 DE is delivered at a minimum
temperature of
50 °C because of the possibility of crystallization below that
temperature,
63DE at a temperature of 40 45°C and high fructose at 28 30 °C.
It is important to note that
63DE glucose syrup, in
particular, will increase its solution colour on storage. Consequently,
a
dematerialized form is necessary if the product is to be stored for up
to three
weeks.
Manufacture. Glucose syrups
are manufactured by the
acid and enzyme hydrolysis of starch, normally of maize or wheat
origin. This
treatment breaks down the long chain carbo hydrate molecules into a
spectrum of
simple and higher sugars.
If this
conversion is allowed to continue, the end products are dextrose and
maltose.
However, under controlled conditions syrups of defined composition can
be
produced.
The extent of hydrolysis is
defined in terms of dextrose
equivalent (DE): this figure represents the total reducing sugar value
of the
syrup expressed as a percentage of the reducing sugar value of pure
dextrose,
calculated on a dry basis.
Additional enzyme treatment enables
the dextrose content of
syrup to be converted to fructose up to 42%, giving the syrup a greater
sweetening power. This level can be further increased by
chromatographic
enrichment techniques.
Quality
Carbohydrate sugars are used
in carbonated soft
drinks not only to provide a level of sweetness to balance flavours and
acids
present but also to provide mouth feel to the product by increasing its
viscosity and dissolved solids content. They also provide an easily
metabolized
source of energy, a fact utilized in the marketing of certain health
related
soft drinks. The carbohydrate sugars incorporated therefore require to
be of a
consistently high quality in their physicochemical properties.
1. Trade requirement
Carbohydrate sugars are
generally supplied to
quality specifications agreed with soft drinks manufacturers and can
vary
depending on the products into which they are to be incorporated and
the
particular processing techniques involved at manufacturers premises.
Extraneous matter. The levels
of extraneous matter
are of particular concern because of (a) their effect on the appearance
of the
final products and (b) the possibility of loss of carbonation if
excessive
sites of nucleation are present.
All liquid products supplied
(such as liquid sugars
and the various types of glucose syrup) can, by virtue of their
physical
characteristics, be filtered before despatch thus minimizing the above
problems.
Granulated sugars, although
prepared from syrups
that have undergone numerous filtration processes, can contain levels
of
extraneous or water insoluble matter depending on the country of
origin. In the
UK these levels are extremely low, typically of the order 6 mg/kg
sugars, as
determined by a membrane filtration method.
Every precaution is taken to
minimize the presence
of this water insoluble matter, which can consist of filter aid or
calcium
salts from the manufacturing process. It may therefore be prudent for
soft
drinks manufacturers to consider the filtration of liquids prepared
from
granulated sugars using a filtration system of adequate porosity
commensurate
with realistic filtration rates.
Colour in solution.
Especially for those carbonated,
soft drinks, which are clear in appearance, carbohydrate sugars of a
low
solution colour are a prerequisite. In the UK this standard is
obtainable, but
in other less developed countries further treatment of sugars after
receipt is
necessary in order to conform to this level. The treatment used is
normally
that of filtration through plate and frame filters incorporating carbon
sheets.
The production specifications
of some international
soft drinks companies list the use of these carbon filters for all
locations in
order to cover the worldwide production of soft drinks, with
carbohydrate
sugars of differing quality parameters. In those countries whose
carbohydrate
sugar quality can be guaranteed to be of the highest order, the use of
these
filters may be negotiable.
Acid floc. Floc formation in
carbonated soft drinks
is a phenomenon observed in acid solutions and normally appears as a
white
precipitate. This precipitate can take the form of loosely aggregated
particles
floating within the solution which, in extreme cases, may take on the
appearance of well teased out cotton wool or as more dense particles
that sink
through the solution. On shaking the solution the floc usually
disappears as
the weak forces between the molecules are disrupted.
Floc has been shown to be
associated with sugars
(both beet and cane) and also with polysaccharides present in water as
a result
of the growth of algae and chemicals from water treatment.
Sugar floc is normally
associated with sugars of low
quality and these have caused final product problems in some countries.
For
this reason, the National Soft Drink Association standards include a
method for
the evaluation of floc producing substances. This is the Spreckles
Qualitative
Floc Test Procedure.
Since the National Soft Drink
Association makes
reference to the testing of sugars from beet for floc evaluation, the
sugar
beet industry in the UK has made extensive efforts over the years to
ensure
that all granulated sugars and liquid sugars are free of any substances
that
could lead to acid floc.
Microbiological. The low
moisture content, typically
0.02% w/w, of granulated sugar coupled with its high purity minimizes
the
possibility of microbiological degradation. In solution, carbohydrate
sugars
generate high osmotic pressure, which is a major factor in protecting
concentrated solutions from microbiological contamination. However, if
granulated sugar is allowed to become damp and syrups are diluted, then
an
increased risk of microbiological degradation occurs. This can happen
if there
are deficiences in storage conditions.
In the UK carbohydrate sugar
manufacturers target
levels for mesophilic bacteria, yeasts and moulds in liquid products
are the
standards for Bottlers liquid sugars as defined by the National Soft
Drink
Association. By comparison the target levels for granulated sugar are
twice the
National Soft Drink Association standards. This difference relates to
the fact
that, by virtue of their physical form, liquid products can be treated
by
filtration and ultraviolet radiation to reduce further any
microorganisms
present.
An additional protection
operated by some sugar
manufacturers is to control the pH of the liquid products to about 8 to
reduce
even further the chance of spoilage.
In practice, carbohydrate
sugar manufacturers
undertake regular sanitising programmes of their production and storage
systems
coupled with comprehensive quality assurance and control, not only to
ensure
minimal levels of spoilage organisms, but also to ensure freedom from
pathogenic bacteria.
2. Quality assurance
management
Soft drinks manufacturers in
the UK have for some
time required guaranteed quality raw materials especially as they
introduce
Supplier Assurance Systems and Good Manufacturing Practices.
Carbohydrate sugar
suppliers have responded positively to these requirements by
instigating their
own quality assurance systems, including certification to British
Standard 5750
and the International Standard ISO 9000.
These quality management
systems involve documented
procedures and instructions, which are self and externally audited,
concentrating on all key activities affecting quality of products and
service.
3. Sugar analysis
The methods generally used in
the analysis of
sucrose products are those defined by The International Commission for
Uniform
Methods of Sugar Analysis, normally referred to as ICUMSA. Many of
their
methods have been adopted by the European Economic Community and the
Codex Alimentarius
Commission. The analytical methods used by glucose syrup manufacturers
are
generally those standardized by the Corn Refiners Association.
Transportation and delivery
The mode of transportation of
carbohydrate sugars
depends on the type of sugar involved and also on the sophistication of
the
transport system and reception facilities available in any particular
country.
Less developed countries normally rely on granulated sugar contained in
bags.
Ideally this sugar should, for ease of handling, be palletized and
transported
within covered wagons to reduce contamination of the packaging
material, which
could eventually contaminate the contained sugar.
1. Bulk delivery of
granulated Sugar
Demand by soft drinks
manufacturers for bulk
deliveries has grown rapidly over the past years since their use offers
a
number of important advantages over bagged supplies. The advantages
relate to:
savings in storage space savings
in
manpower, both at the reception point and during internal redistri bution improved
hygiene and the possibility of
automated processing to which the system lends itself.
Bulk deliveries are made in
road tankers, which are
specifically designed to maximize efficient discharge of the sugar and,
by
virtue of the materials used for construction, to minimise product
contamination. Additionally they are designed for ease of internal
cleaning,
which should be carried out at regular intervals.
Grape juice processing
History of grape juice processing in North America
The fruit juice processing
industry of the United
States is said to have been started by Dr Thomas B. Welch and his son
Charles
in Vineland, New Jersey in 1868. By applying the theory of Louis
Pasteur to the
processing of Concord grapes, they were able to produce an unfermented
sacramental
wine for use in their church. By 1870 this grape product was being
produced on
a small scale for local church use.
By 1893, grape juice had
become a national favourite
beverage in the United States as thousands sampled it at the Chicago
Worlds
Fair. It was during this year that Dr Charles Welch turned his full
attention
to the marketing of grape juice. In 1897 a new plant location was
chosen for
processing operations at Westfield, New York. Some 300 metric tons of
grapes
were processed that year in
1989 Welchs,
now one of the largest producers of processed grape juice in the world,
handled
some 186000 metric tons of grapes.
Grape cultivars
In the United States, four
broad classes of grapes
are grown: Vitis lubruscana, hybrids of the northeastern United States
native
grape Vitis
vinifera, European grapes
common to California area Vitis
rotundifolia, the southern and southeastern Muscadine grapes and French hybrids. Prior to
the discovery of
the Americas the species, Vitis vinifera, supplied the known worlds
grapes.
Vinifera grapes are still among the most important in the world but in
harsh
climates these grapes cannot tolerate severe winters, diseases, and
pest
problems.
When selections of Vitis
lubrusca were crossed with
other grapes, new varietals were produced, such as Vitis lubruscana.
Ephraim
Bull was a horticulturalist who pioneered in this cross breeding and
selection
process with native American grapes. The Concord grape, a varietal
almost
synonymous with grape juice in the United States, was a seedling that
Bull
found in his vineyard. Its parentage is still unknown. Virtually the
entire
unfer mented grape
juice industry has
developed from this one cultivar.
The average production of
Concords is approximately
4 5 tons per acre in eastern United States. Yields can reach 7 8 tons
in
western states. Cultural practices such as irrigation, pruning severity
and
fertilization can have a very significant influence upon the quality
and
quantity of grapes harvested.
There are now many hybrids of
the native species
available for use in the industry. Some of the older cultivars are:
Catawba,
Delaware and Niagara. The Concord grape, grown throughout the cooler
regions of
the United Slates and Canada, is still the principal grape for the
industry.
Though not possessing as
large a market shares in
unfermen ted grape juice, there are some Vinifera grapes processed into
grape
juice. They tend to be much higher in sugar and lower in acidity than
the
Lubruscana grapes, and consequently are not as flavorful.
The genus, Vitis, is
generally considered to consist
of two sub species, Euvitis and Rotundifolia. All grape species other
than
muscadines fall into the Euvitis sub genus muscadines
alone make up the sub genus,
Rotundifolia. For this reasons some botanists do not classify
muscadines as
grapes. Some basic differences are identifiable such as clustering of
the
berries and pit configuration however,
muscadines are utilized in an identical fashion and treatment as the
Euritis
sub genus. Conse quently, in matters of commerce and functionality,
muscadines
are considered grapes.
The chemistry of grape juice
The quality of grape juice
can be described almost
entirely by its chemistry. Its color is caused by anthocyanins, their
glucosides and condensation products, its taste by acids, sugars and
phenolics
its aroma by a diverse mixture of volatile secondary metabolites in
very low
concentrations. Since 1967 over 1000 research papers have been
abstracted by
Chemical Abstract Service describing the chemistry of grapes and grape
juice.
In these papers thousands of chemicals and their reactions in grapes
are
described. However, only a small percent of these chemicals are
responsible for
the quality attributes that people perceive when they drink grape
juice. Table
1 lists the major components of grape juice, their concentrations and
Inequality attributes they determine.
This table shows clearly why
it is possible to
predict sweetness sourness and acidity in grape juice by measuring
certain
carbohydrates and organic acids. These compounds are major constituents
of
grape juice and are measurable by some very simple techniques. For many
years
the sugar and acid content of grapes have been used to set standards of
quality
resulting in new horticultural and processing techniques that modify
the sugars
and acids in grapes in order to optimize juice quality. These
developments are
the direct result of our knowledge of the chemical causes of quality
and the
availability of tools to measure them. However, the volatiles that
cause aroma
are present in such minute quantities that most of them are still
unknown and
those that are known generally require the most advanced chemical and
spectroscopic techniques to quantify them.
Although the methods of
chemical analysis that
define a quality grape will continue to develop and improve, there is
another
approach, sensory analysis. This involves the deter mination of quality
attributes using methods from the sciences of behavioural psychology
and
sensory perception. These methods relate the human perception of
quality to
food components. Instead of using chemical reactions and physical
measurements,
sensory analysis uses human subjects as tools to determine quality by
measuring
their behaviour when they are subjected to the food. A review of
sensory
methodology as it relates to the optimization of quality attributes is
given by
Moskowitz.
1. Carbohydrates
Carbohydrates are the most
abundant component in
grapes. On average, grapes have per 100 g, 6.2 g glucose, 6.7 g
fructose, 1.8 g
sucrose, 1.9 g maltose and 1.6 g of other various mono and oligosaccharides. Pectic
substances, which
act as the intercellular cement, are a mixture of numerous long chain
carbohydrates and related compounds, which occur in solution and/or
colloidal
dispersion in grape juice.
2. Acids
Tartaric acid is the
predominant acid in grapes and
accounts for the tartness of the juice. Tartaric acid is present as the
D isomer
and malic acid as the L isomer. Other acids present in minor amounts
include
citric, lactic, succinic, fumaric, pyruvic, a oxoglutaric, glyceric,
glycolic,
dimethyl succinic, shikimic, quinic, mandelic, cis and
trans aconitic, maleic and isocitric
acids. The resulting pH of grape juice can range typically from pH 3 to
pH 4
depending upon variety, climate and soil conditions.
3. Mineral content
Although differences among
varietals in mineral
content are not typically noted, differences during maturation have
been
studied. Mineral anions and cations are taken up at a relatively
constant rate
and distributed throughout the system resulting in a relatively poor
concentration in the berry compared to other parts of the wine. During
maturation heavy metals increase by as much as 50%. Phosphate content
increases
in both the peel and the pulp.
4. Phenolics
The color of Concord grapes
is due in large part to
the anthocyanin pigments located in and adjacent to the skin. These
pigments
are extracted by heat and/or fermentation. Seven individual color
components
have been identified in Concord juice, the major contributor being
delphinidin
monoglucoside. The phenols typically found in grapes include benzoic
acids,
cinnamic acids, flavonols, anthocyanidins as well as various flavans,
which
constitute the tannin precursors.
5. Volatiles
Maarse listed 500 volatile
compounds in grapes but
most of these compounds occur at levels well below their detection
threshold.
Only a very few seem to evoke sensation and affect perception.
Furthermore. The
odor active molecules have no identifiable chemical features that
distinguish
them from the more prevalent odorless volatile compounds. The odor
active
volatiles in Lubruscana grapes come from different metabolic pathways.
2,5 Dimethyl
3 (2H) 4 furanone, a sweet strawberry smelling compound, is produced
from
carbohydrate metabolism. Ethyl 3 mercapto propanoate, with a foxy
smell, methyl
anthranilate with its Concord smell and the floral smelling 2
phenylethanol are
formed from amino acids, while beta damascenone with a rose like aroma
and
linalool with the aroma of orange peel oil are derived from terpenoids.
The
green leaf like smelling (E) 2 hexenol is a lipid oxidation product.
This diversity results in a variety
of processing effects on
the aroma of grape products. For example, the heat treatments used in
color
extraction, depectinization, juice concentration and pasteurization
cause beta damascenone,
vanilin, and/or methyl anthranilate to dominate the aroma of certain
cultivars.
Modern grape juice processing
1. Harvesting/ripening
Grape juice consists of a
natural aqueous mixture of
various carbohydrates, organic acids, anthocyanins and flavor
compounds. In the
soluble solids of grape juice, the primary sugars are glucose and
fructose. In
unripe grapes, glucose accounts for as much as 85% of the sugar
content. As the
grape approaches full ripeness there is generally a slight excess of
fructose.
Sugars are manufactured in the leaves via photosynthesis and
translocated to
other organs, particularly the berries, as needed. It is the sugar
content of
the grapes, which often is the basis for purchase and a primary
indicator of
optimal harvest time for grape juice production.
A typical level of acidity at
time of harvest in
Concord grapes is 1.3 g/100 ml as tartaric acid. This acidity generally
starts
quite high in the grapes and decreases as ripening takes place. Optimum
ripeness is often associated with balanced levels of sugars and acids.
On
occasion, tannins, color and aroma are also considered. Although
acidity levels
of Concord grapes at harvest are very high, cold temperature storage
(32°F) of
the grape juice extracted from these high acid grapes will induce a
detartration and reduction of total acidity to more acceptable levels.
Degrees
Brix, a refractive index based measurement of soluble solids, is the
primary
method used in grading grapes at harvest, which are scheduled for juice
production.
Mechanical harvesting has
greatly improved the
efficiency and speed of bringing grapes from the vineyard to the
processor.
Mechanically harvested grapes are handled in bulk boxes (47 x 42 x 38
inch)
equipped with polyethylene liners. These boxes will hold approximately
1 ton of
grapes. Studies have shown that mechanically harvested grapes actually
contain
fewer stems and trash than hand harvested grapes. This is important due
to the
detrimental effect of materials other than grapes on the quality of
expressed
grape juice. These boxes can be expected to have approximately 21 inch
of free
run juice in them because of mechanical damage, vibration and weight of
grapes
from depth of load.
The Chisholm Ryder grape
harvester is a self propelled
system that straddles the rows of vines and is one of the most commonly
used
harvesting units. This harvester bats off the grapes and grape clusters
with
metal or rubber like strips as it moves down the length of the row. The
grapes
fall onto a series of collector leaves located on either side of the
unit
underneath the vine being harvested. These rotating leaves then
transfer the
grapes to conveyers, which carry them to the top of the harvester unit
and dump
them into a transfer chute for filling of a bulk bin separately
transported by
truck.
Bulk bins of grapes are
transported to a grading
station where core samples are taken from each bin and combined to form
a load
sample. This is used to measure the soluble solids (Brix) upon which
payment
for the load will be based. Grapes are typically processed within 4 6 h
of
picking.
Most grape juice processed in
the United States is
made from Concord grapes. A significant volume of literature can be
found
concerning grape juice processing and some reviews of the technology
are also
available. A typical process outline is described below and shown in
Figure 2.
2. Stemmer/Crusher Operation
Grapes at the plant are first
conveyed to a
stemmer/crusher, which removes residual stems, leaves and petioles from
fruit.
This unit is designed around a rotating perforated drum. The
perforations are
approximately 1 inch in diameter and generally cover the entire drum.
In the
process of traversing the rotating drum, grapes are caught by the
perforated
drum and knocked from the stems. The individual grapes are broken open
or
crushed in the process and drop through the drum. Stems and leaves,
etc.
continue on in the center of the drum and are discharged at the end for
waste.
3. Hot break process
Once the stemmed/crushed
grapes are separated from
the vines they pass
through a large bore
tubular heat exchanger where they are heated to 140ºF. This is known as
the hot
break process and it is primarily designed to extract a large amount of
color
and assist in maximizing the yield of juice. To the hot grapes is added
a
pectolytic enzyme and in the case of the typical process shown here,
Kraft
(wood pulp) paper (actually spent filter media from the rotary vacuum
juice
filter) is added to serve as a press aid.
The addition of press aid to
the mash provides
firmness and exit channels for the juice. Sterilized rice hulls,
bleached Kraft
fiber sheets or rolled stock and ground wood pulp are common press aids
used
commercially. Ideally, a rotary filter press aid should have relatively
long
fibers and it should be able to be separated with a minimum breakage of
those
fibers for maximum effectiveness.
Soluble pectin is found in
the juice and is a result
of pectolytic enzymes which are primarily located in the cell wall of
the
grape. This soluble pectin causes difficulties in pressing due to the
lubrication it affords the press cake and the consequential reduction
in screw
press effectiveness. Typically, 50 100 ppm of a pectinase enzyme is
sufficient
for the de pectinization process at this stage. De pectinization is
designed to
reduce the slippiness of the pulp and thus permits the effective use of
a screw
press when combined with wood pulp bulking agent. Enzyme treatment is
allowed
to continue for about 30min prior to pressing. Several de pectinizing
tanks are
employed so that a continuous flow may be maintained to the presses.
4. De juicing/pressing
operation
The mash is generally hot
pressed in order to
maximize yields and color extraction. Hot pressed juice is higher in
total
solids, tannins, anthocyanins and other matter. Control of the combined
hot break/hot
press procedures is important because the extraction of astringent
materials
(i.e. tannins) will increase with time and temperature of these two
unit
operations. Phenolic compounds contribute to both the color and the
astringency
of grape juice. The extraction of both the phenols and the anthocyanins
is
greatly affected by the degree of heating used in the hot break
process. In
general, the longer and hotter this process, the more significant the
extraction process.
The de juicing or pressing
operation can utilize a
number of different equipment variations. These include screw,
hydraulic, belt
and pneumatic presses. Selection of the equipment can depend on
production
capacity, juice yield, desired level of automation, availability of
manpower,
operating cost and required capital investment.
The hydraulic rack and frame
press was the mainstay
of the grape juice pressing operations for many years. Heavy cotton or
nylon
cloths were filled with a set amount of mash and then folded to produce
what is
called a cheese. The individual cheeses were stacked and separated by a
wooden
or plastic lattice work. The combined stack was then compressed using a
hydraulic ram during which the juice was expressed.
The Bucher Guyer Press is a
highly automated
pressing system used in a batch pressing operation. Generally this
system
requires no press aid. The system consists of a rotable cylinder with a
hydraulic ram used for juice expression. Within the cylinder are fabric
covered
flexible rubber rods. The rods have longitudinal grooves, which allow
the juice
to transport easily to the discharge port.
The wilmes press is a
commonly used system for grape
juice pressing. It is a pneumatic based system consisting of a
performed,
rotable horizontal cylinder with an inflatable rubber tube in the
center. The
cylinder is filled with grape mash through a door in the cylinder wall,
which
is rotated to the top position. After filling, the press is rotated to
ensure
even filling. During this rotation the air bag is filled, creating the
mash
compression action. The bag is then collapsed and the cylinder is
rotated. The
rotation and pneumatic compression of the mash is repeated many times
with increasing
air pressure.
The de pectinized mash
produced in the hot break
process can be passed over dejuicing screens where 50 60% free run
juice is
removed. With this low technology step, the mash to be pressed is
reduced by
approximately half. The dejuiced pulp is then pressed in (horizontal or
vertical) screw presses. The typical screw press consists of a
reinforced
stainless steel cylindrical screen enclosing a large bore screw with
narrow
clearance between the screw and the screen. Breaker bars are typically
located
between the screw intervals in order to disrupt the compressing mash.
Backpressure is provided at the end of the chamber and is usually
adjustable.
Typical capacities for screw presses with a 12 inch and 6 inch diameter
are 5
and 15 tons/h, respectively.
The Serpentine belt press,
the Ensink and other belt
presses are effective for grape juice processing. In belt presses, a
layer of
mash is pumped onto the belt entering the machine. Added press aid is
usually
required for improved yield and reduced suspended solids. The belt is
either
folded over or another belt is layered on top of the one carrying the
mash. A
series of pressurized rolls compress the enveloped mash. Expressed
juice is
caught in drip pans. The cake is discharged after the last pressure
roller.
The waste pomace from any of
these systems may be
repressed for improved yields of an additional 3 5 gallons of juice per
ton
leading to a total juice yield of 200 205 gallons per ton. Extraction
of the
pomace using hot water, in a plant equipped with concentration
equipment, can
recover additional soluble solids in the juice. This secondary
extraction, when
handled with are will produce a low soluble solids liquor which will
have no
odor or taste defects. This low flavour impact, low soluble solid
extract can
be recombined (in natural proportions) with single strength juice
intended for
concentration.
All pressing operations must
be able to deal with
free run juice and in some cases handle it with special care to give
the
highest possible product quality. In comparing the different press
types, the
screw press is probably most popular, however, this is highly dependent
on
required yields, available capital at purchase and smoothness of
integration
into current operations.
5. Coarse filtration
The pressed juice is merged
with free run juice and
accumulated in slurry tanks where the press aid, usually paper or wood
fiber is
added at the rate of about 15 lb/ton of grapes. The paper, which
typically
comes in 1 Ib sheets, requires very heavy agitation to break it up and
disperse
it throughout the juice. Alternatively this paper may be shredded
first. Having
been dispersed, this paper serves as filter media for the rotary vacuum
belt
filtration that follows.
Prior to filtration the
insoluble solids (ISS)
content of Concord juice pressed with paper (measured volumetrically by
centrifugation) can reach 10 12%. Without paper, pressing is extremely
difficult and produces juice containing up to 30% ISS. After filtration
through
the belt and paper, insoluble solids will be 1% or lower. The spent
paper
discharging from the belt is then re slurried into the fresh hot grapes
entering the system just prior to the treatment tanks thus
the paper serves the dual function of
filter media and press aid.
The importance of achieving
low ISS cannot be
overempha sized for two reasons: (i) high efficiency heat exchangers
used for
pasteurization have very small clearances between plates and tend to
plug over
a period of time with high levels of insolubles (ii)
any insolubles remaining will ultimately
settle to the bottom of the storage tanks. The actual volume of bottoms
is
dependent primarily on the level of insolubles in the initial juice and
the
filtration of bottoms juice containing high levels of insolubles is
difficult and
costly.
6. Bulk storage and tartrate
precipitation
A common practice is the
storage of single strength
grape juice in bulk storage tanks. The tanks themselves are pre cleaned
and
then filled with clean municipal ice water for periods of 1 4 weeks
prior to
use. This water is then used for cooling processed juice during the
periods of
highest process demand thereby dramatically reducing the immediate
refrigeration needs. Air inlets at the tops of these tanks are
generally fitted
with absolute sterile air filters in order to ensure no airborne
contamination.
In the actual process,
filtered juice is pasteurized
at 185 190°F for a minimum of 1 min. The heat exchanger system utilized
in this
step, cycles through a cleaning every 24 h. Hot caustic, followed by
200 ppm
chlorine solution, followed by 185°F hot water rinse is the usual
sanitizing
method. By proper flow design this cleaning approach can be used for
not only
the heat exchangers but also for all the feed lines to the storage
tanks. Once
the juice is properly pasteurized it is immediately cooled using a
regenerative
heat exchanger, to 30 32ºF prior to storing in refrigerated tanks.
The entire system is treated
much like an aseptic
process. Special care is taken to avoid any dead ends or other such
areas for
contamination buildup. Use of heat exchangers for the cooling process
is
required in order to deliver juice at proper temperature to the storage
tanks.
Failure to reach storage temperature prior to delivery of juice to the
tank
will cause the tank to remain above proper storage temperature
excessively
long.
These tanks, which typically
are either stainless
steel or Food Grade epoxy lined cold rolled steel, are not truly
aseptic but
nevertheless are carefully sterilized prior to introduction of any new
juice.
Design of the tanks allows for complete filling up to a top manhole.
The
manhole top is usually equipped with an ultraviolet lamp to preclude
the growth
of mold. Tank capacity varies typically in a range of 150000 320000 US
gallons
but can range over 700 000 gallons. Juice processed in this manner and
held at
28 30ºF is very stable and has been held for over 1 year without any
evidence
of fermentation. Obviously, stringent sanitation requirements are
necessary.
Processing of citrus juices
Introduction
The citrus growing areas in
the United States are
located in the States of Florida, California, Texas and Arizona. The
largest
crop is harvested in Florida where over 90% of the oranges and
approximately
55% of grapefruit are processed into juice products. Brazils crop is
larger
than Floridas, where even larger percentages of oranges are processed
for
juice. Other citrus growing areas in the Western Hemisphere include
Mexico,
Central America, Puerto Rico, Jamaica, Dominican Republic and countries
on the
northern part of South America. The machinery used for the processing
of citrus
juices in these countries and in other regions, such as Spain, Italy,
Israel
and around the Mediterranean is quite similar.
Most of this chapter deals
with the processing of
oranges in the State of Florida, USA, with which the author is most
familiar.
The handling of grapefruit, tangerines, lemons, limes, etc., is quite
identical
in most ways to that of oranges, though some of these citrus varieties
require
additional process equipment for certain by products.
The basic unit in Florida for
describing the size of
the orange crop is the fruit box. A box of oranges, by definition,
weighs 90 Ib
and a box of grapefruit weighs 85 Ib. The harvesting season crosses
over the
New Year and has a duration of 7 10 months, depending on varieties 123 100 000 boxes of oranges
(61 550 US tons)
were harvested during the 1986 1987 season of which 92% went to
processing, the
balance going to the fresh fruit market. In the same season, 49 800 000
boxes
(2116 500 tons) of grapefruit were harvested with 56% of the crop
processed for
juice. Of the approximately 113 million boxes of oranges processed in
the 1986 1987
season, the juice from 96 million boxes was concentrated to make frozen
concentrated orange juice (FCOJ).
By products resulting from
the processing of citrus
fruit include dried peel for livestock feed, molasses concentrated from
liquid
pressed from the peel, commercial d limonene, which is distilled peel
oil, and cold
pressed oil, the processes of which are discussed later in this
chapter. The
production of livestock feed from the processing of all varieties of
citrus in
Florida for the 1986 1987 season was 600 626 tons of dried peel and 27
811 tons
of molasses. d Limonene production was 13 483 000 Ib.
Fruit harvesting and transport
The harvesting of citrus
fruits in Florida begins
when the fruit reaches maturity standards set by the United States
Department
of Agriculture (USDA) and the Florida Department of Citrus. For juices,
these
regulations have to do with Brix acid ratio color, oil content, etc.
and in
general are set to ensure quality products.
The picking of fruit for the
orange juice market
begins in September with most of the juice going to the single strength
market.
There are four main varieties of oranges growing in Florida for the
juice (and
fresh fruit) market. The earliest oranges consist of Hamlin and Parson
Brown
varieties. These early fruits are harvested mostly from October to
December.
Mid season fruit (called Pineapple oranges) mature during the first 3
months of
the year. Late season fruit (Valencia oranges) are harvested from March
to
June.
The production of FCOJ
usually begins early in
December when the soluble solid (sugars) content is around 12%
(12°Brix). With
evaporators operating at full capacity, concentrate production drops by
5% if
infeed Brix is 11.5° instead of 12°.
Hand picked and mechanically
harvested fruit are
brought from the groves to the roadside and loaded into trucks (tractor
trailer
type), which hold 500 550 boxes of fruit. The trailers are then trucked
to the
processing plant.
Unloading and storage of fruit
These operations are shown
diagrammatically in
Figure 1. The trailers are approximately 8 ft wide x 40 ft long.
Trailer sides
extend approximately 5 ft above the bed of the trailer. After weighing,
the
trucks are hauled to the unloading ramps where they are inclined and
unloaded
through a gate at the rear of the trailer. There are various types of
unloading
ramps used, the most historic of which is a fixed back over or fixed
back down
ramp. As the crop size grew and processing plants became larger, a need
for
quicker unloading became necessary and the trend now is to convert to
hydraulic
ramps for lifting and tilting the trailers. Of these, there are two
types, the
back into and the drive through arrangement.
The older fixed back into
ramps are concrete slabs
with a 10º slope from horizontal. Because of the fixed slope of the
incline and
associated clumsy traffic patterns, a good average unloading rate for
one ramp
is about three loads per hour. This would allow an infeed fruit flow of
1500
boxes h or 65 70 tons raw oranges per hour. Other disadvantages include
the
varying height of different trailer beds above the road, which
sometimes requires
manual fixing of fill in ramps or wheel elevating shims before the back
gate of
the trailer can be opened.
The drive through type
hydraulic ramp allows for the
most favorable traffic patterns, adjustable tilting to accelerate the
rolling
of fruit near the end of the unloading cycle, and an adjustable
hydraulic back
stop and fill in ramp which can be completely lowered to facilitate
driving
through. Unloading ramps of this design can handle up to six trailers
per hour
(3000 boxes of oranges per hour).
One of the problems facing
the unloading staff is
the accumulation and disposal of leaves, stems, dirt and even small
branches
that arrive with the load. The amount of trash has increased over the
years as
plants grew and as the percentage of mechanically harvested fruit
increased. In
the path of flow from the trailers to the storage bins, the fruit may
travel
over a gravity bar grate, roller spreaders, belt conveyors, chutes,
elevator,
etc., and in each of these transitions, leaves and stems must be
contended
with. Bar grates and roller spreaders will drop some of the small,
loose pieces
through their open spaces to a collection pit, which needs periodic
sweeping
and shoveling. Conveyor transfer gates and elevator chutes sometimes
become
clogged. The clean up and manual disposal of this trash requires
considerable
man hours throughout the production day. Many attempts have been made
to reduce
the labor required for this clean up by mechanically conveying the
trash from
under bar grates and roller spreaders. Screw conveyors are not
completely
suitable for elevating the trash out of the pit as the longer stems
will wind
their way around the shaft, accumulate other pieces and stop the flow.
The latest solution to the
trash problem is the
installation of machinery similar to that used in the corn industry for
husking
corn. These units consist of feeder and distribution belts, which put
the fruit
in single file through a belt and roller arrangement that not only
drops out
the loose trash but will pull off stems that are attached to the fruit.
The use
of this type of equipment requires 10 12 ft headroom to complete all
the
gravity transfers of fruit and trash through it to other conveyances.
Layout of this type of
equipment depends on
availability of plant space. Florida surface water tables are not too
far below
ground level so deep pits are not always feasible and careful attention
needs
to be paid to the type of conveyors, elevators and transfer points.
Dirt and
small pieces of trash will pass through transfer points, especially
under the
fruit wipe off on belt conveyors and on the bottom of bucket type
elevators, so
there still needs to be access under these conveyors for periodic clean
up.
On its path to the storage
bin the fruit passes
through a sampler, a device which takes an on line sample of the
incoming
fruit. The sampler is usually located after the fruit is elevated, and
the
fruit drops through chutes to the State Test Room. An approximate 40 Ib
sample
of raw fruit is run through a state test room extractor and tested for
yield,
soluble solids content, Brix and acidity.
Next in the path of fruit
flow is a grading station,
where unsuitable fruit is culled out and attached stems that have
passed
through the trash removal equipment are removed. The grading stations
consist
of roller spreaders with grading personnel picking out the culls and
dropping
them through a chute to a conveyor (usually a screw conveyor) that
transfers
them to the cattle feed production part of the citrus plant, referred
to as the
Feed Mill.
An unloading station that can
handle six loads per
hour requires a grading station capable of removing culls
(unsatisfactory
fruit) from fruit that passes at a rate of fifty 90 Ib boxes of oranges
per
minute. One box of oranges lying single height requires approximately
13 ft2 of
area on a conveyor belt and grading table. A grading table consists of
a roller
type conveyance that spreads the fruit across the table and conveys
them
forward at about 60ft/min. The widest tables are 52 inch across the
rollers
with grading personnel on each side. Grading personnel are spaced about
48 inch
apart with drop chutes between them. A single 52 inch wide grading
table x 10ft
long with six people will ideally handle 20 boxes of oranges per
minute. However,
since the fruit will be graded again on its path to extraction, the
unloading
grading tables are pushed harder, allowing for two tables per unloading
ramp,
each handling approximately 25 boxes per minute. After grading, the
fruit
travels through belt conveyors and elevators to the fruit holding bins.
The holding bins are
constructed with steel columns,
beams and braces with either wood slats for siding or flat mesh
expanded metal.
They are usually constructed in parallel rows with each bin having a
capacity
to hold one truck load. Each bin has approximate dimensions of 10 x 10
x 25 ft
high and the succeeding bins have common walls. The two rows of bins
are fed
with a bell conveyor equipped with manually set wipe offs and gates for
feeding
the individual sections. The fruit enters the bins through inclined
ramps that
more or less cause the fruit to roll down in a spiral motion so that
dropping
and bruising is minimized. The inclined ramps are located so that the
total
weight of the load is distributed throughout the height of the bin to
prevent
squashing of the fruit at the bottom.
Fruit transfer from storage bins to extractors
The introduction of fruit
into the processing plant
begins with the bin operator opening gates at the bottom of the bins
where fruit
rolls onto a conveyor belt in the center of the bin rows. The rate of
flow out
of the bins is manually controlled by the bin gate opening and by an
adjustable
vertical gate at the end of the bin take out conveyor. The processing
buildings
are located at some distance from the fruit bins in order to be away
from the
flies and other insects that tend to inhabit the bin area. Belt
conveyors and
bucket elevators bring the fruit to a height suitable for gravity flow
through
washing, grading, sizing and extractor feed.
The elevated fruit usually
drops into a fruit surge
bin located just outside the extractor room with a volume capable of
holding 5 10
min of fruit. The surge bin is equipped with level switches which send
signals
to the fruit bin operator and extractor operator, for purposes of
regulating
flow. The surge bin take out conveyor has a variable speed drive that
is
controlled by the extractor operator so that fruit flow rate coincides
with
juice demand.
From the surge bin, the fruit
is discharged onto a
roller spreader and from there it enters a brush washer. The washer
consists of
a series of rotating cylindrical brushes turning in the direction of
the fruit
flow. Detergent is added at the fruit inlet end and water is sprayed
over the
spinning fruit. Most Florida citrus processors use evaporator
condensate (the
water removed from the juice in the concentrate process) for washing
fruit.
Just downstream from the
washer are located further
grading tables where unsuitable fruit is graded out by personnel on
each side the culls
are dropped through chutes and
conveyed to the feed mill.
After grading, the fruit
travels through another
roller type device similar in design to the grading tables but used to
spread
the fruit into a pattern feeding the total width of the fruit sizer.
The sizer
consists of several narrow belts running in parallel and tilted so that
the
fruit travels in single file along the low edge of the belt and against
a
rotating roller that can be adjusted up and down. Juice extractors
require larger
and smaller cups for different size ranges and the actual construction
of the
sizer depends on type and number of juice extractors. Each roller bay
of the
sizer is adjusted to suit the size variations of the incoming fruit.
Extractors
have constant speeds and only meet maximum capacity when their feed
chutes are
kept full. The extractor room people must make periodic checks and
adjustments
of sizer roller spacing, gates and lane dividers to ensure that the
extractor
room is not the bottle neck of the process.
The sized fruit drops through
chutes to a
distribution belt that feeds the extractors. This belt conveyor travels
the
full length of a row of extractors plus a few more feet to accommodate
the
drive and drop out for overflow fruit. The top belt is tilted toward
the
extractors and separated into lanes for conveying the larger fruit past
the
smaller cupped extractors as the sizer above is not as long as the
total row of
extractors. The distribution belt is equipped with gates and wipe offs
that can
be set to maximize the extraction efficiency.
The return side of the
distribution belt is usually
a few feet lower than the top or feed side of the belt. Along the feed
flow
between extractors that change cup size, is a wipe off and an overflow
chute
that drops fruit to the return side of the distribution belt. The
overflow
fruit travels back towards the front end of the system, is wiped off,
conveyed
and elevated back to the fruit surge bin. Fruit sizing must be set to
ensure
that the fruit surge bin does not accumulate loo many of one size,
which would
limit the capacity of the extraction operation.
Juice extraction and finishing
1. Extractors
There are two types of
extractors in common use in
the Citrus Processing industry, both originating in the United States.
One type
is manufactured by FMC and the other by Brown Citrus Machinery.
Extractors are
leased on a royalty basis and the equipment is owned and serviced by
the
extractor manufacturer. In Florida there is about an even split between
the two
types and the advantages one has over the other are best extolled by
the
respective suppliers. Both types produce a juice yield and quality
sufficient
to meet high technical standards and profitability.
Extractors are lined up along
the length of the
distribution belt on a platform 8 10 ft above the room floor. The
maximum
number of machines per row is ten (maximum of eight preferred) on the
FMC
extractors and eight on the Brown. Additional in line extractors would
require
wider and more unwieldy conveyor belts.
The FMC extractor is equipped
with a feeder that
runs fruit into the extractor cups in five rows on the five head
machine. Eight
head machines are used for small fruit such as lemons, limes and
tangerines and
three head machines are used for larger oranges and grapefruit. A five
head FMC
extractor, operating at 100rev./min with 90% of the cups full, will
handle 450
fruit/min. During the Florida Valencia orange picking season (March to
May)
most of the fruit will be of a size range that averages 250 fruit per
90 lb box
with a yield of 6 gallons of 12º Brix juice when finished. This is 10.8
US
gallons/min per extractor. However, not all the cups will always be
100% filled
(or even 90% filled), especially the larger cup machines on the end of
the
line.
Fruit is deposited by the
feeder into the bottom cup
of the FMC extractor. The upper half of the cup descends and presses
down on
the fruit, and as contact is made, the sharp end of a round stainless
steel
tube, located inside the bottom cup, is inserted in the bottom of the
orange,
cutting a plug. As the fingers of the top and bottom cup halves mesh,
the fruit
is pressed inward forcing the juice into the tube which is perforated
with
small holes in the cylindrical section and has a restriction in the
bottom to
prevent loss of juice. The resulting internal pressure forces the juice
and
some pulp through the perforations in the tube wall and strains out the
seeds
and larger pieces of pulp. Through precise timing and as the upper half
of the
cup is in the pressing position, the strainer tube containing the
restriction,
plug, pulp and seeds, rises to further press the contents of the tube
and to
eject the pressed plug.
As the two halves of the FMC
cups come together, the
oil cells in the skin of the fruit are ruptured, forcing the oil out of
the
skin where water sprays can be mounted which wash the oil and small
pieces of
skin (crumb) down the outside of the cups and via a screw conveyor to a
cold
pressed oil recovery system. The extracted juice drops into a juice
manifold
connected to the line of extractors, which is sloped in the direction
of flow
toward the final finishing. Ejected peel drops through chutes to a
screw
conveyor located under the extractors, which conveys the peel to the
Feed Mill.
The extractors manufactured
by Brown Citrus
Machinery use a reaming action to extract juice from citrus fruit,
except for
the model 1100 machine which is described later. Of the reaming type,
there are
three models, the most used of which are models 700 and 400. Of these
two types,
the model 700 machines have the highest speed and will handle up to 700
fruit/min. In a line of these extractors, most will be model 700 when
processing oranges, with one or two model 400s at the end of the line
to handle
large fruit. The model 400 can be equipped with larger cups and reamers
and is
also used on grapefruit lines. The Brown model 500 extractor has cups
and
reamers of a smaller size for handling limes and lemons.
The model 700 extractor has a
rotating feeder wheel
with a horizontal shaft and paddles spaced apart on the perimeter of
the wheel.
Fruit rolls from the feed chute into the spaces between the paddles,
which are
timed to rotate and feed fruit cup halves that are connected to
traveling
chains. The cups accept the fruit from the feeder wheel and pass over a
knife
that halves the fruit. The fruit then passes across a slider plate,
which holds
the halves in the cups as they spread apart to feed the reamer wheel.
The reamer wheel also has a
horizontal shaft and is
equipped with reamers at its perimeter that are spinning through gear
action in
the rotating wheel. The cups are so spaced on the chains to match the
position
of the reamers on both sides of the reamer wheel. As cups and reamers
rotate
around, the juice is extracted along with pulp, rag and seed and it
drops down
into a juice trough that feeds the juice finishers. The peel is ejected
from
the cups as the chain returns to the feeder wheel and is dropped to
screw
conveyors to transport the mass to the Feed Mill.
The Brown model 1100
extractor has a feeder that
places the fruit into three single lanes as it enters the extractor. As
the
fruit drops into the extractor it is caught by a series of rotating
discs with
wide angle nearly flat conical shapes on horizontal shafts. The fruit
is wedged
between pairs of discs which forces the fruit across a knife and cuts
the fruit
in half with the skin side of the halves against the discs. As the
discs rotate
the open sides of the halves are forced across a stationary screen.
Juice,
pulp, rag and some seeds pass through the perforations down to the
juice trough
that feeds the finishers. Peel is ejected by the rotation of the discs
after
about 320º of circular path.
2. Finishing
From both FMC and Brown
machines, the extracted
juice needs finishing to separate cloudy but otherwise clean juice from
pulp,
rag, seed and pips. Extracted juice enters the finishers from headers
or
troughs that are sloped toward the direction of flow. The finishers
separate
the pulpy matter from the juice by the action of a rotating auger
inside a
cylindrical screen. The spinning auger forces the pulp out the end of
the
finisher through a valve which is either spring loaded or loaded by use
of an
air cylinder. The valve seat or clearance area is conical and is about
the same
diameter as the screen cylinder (approximately 14 inch in diameter).
Screen
hole sizes range from approximately 0.020 inch to 0.030 inch in
diameter,
depending on the condition and softness of the fruit.
The tightness of the finish
results from the force
applied by the auger against the pressure of the valve. Correct juice
yields
are controlled by adjustable pressures applied in both the extractors
and
finishers. Higher pressures give greater juice yields, however
excessive
pressure can result in off flavors by forcing too much peel and pulp
matter
into the finished juice.
Two finishers are often
placed in series at the end
of the extraction line, the upstream finisher referred to as the
primary
finisher and the downstream called the secondary finisher. The primary
finished
is not set as tight as the secondary unit and so will have a higher
flow
capacity. Sometimes large plants require two secondary finishers in
parallel,
as they will have higher finishing pressures thus less throughput
capacity. The
juice from the primary finisher will be lower in pulp matter and its
juice
stream can be directed to a process that may specify low content of
insoluble
solids.
The amount of pulp allowable
in the final processed
juice is set by plant quality standards and the maximum is set by USDA
and
Florida regulations. Pulp content is tested using a clinical
centrifuge, which
spins a sample placed in a graduated glass tube. Sinking pulp is forced
to the
bottom of the tube and floating pulp appears at the top. The target is
to
achieve 12% or lower total pulp, but the measurement is by volume, not
weight,
as the cellulose matter on a dry basis is only a very small fraction of
the
total weight of the sample.
The pulp discharge off the
finisher is transferred to
the Feed Mill drying operation, or to a pulp wash operation which
yields
further soluble solids by the action of counter current water leaching.
Washed
or unwashed pulp is also sometimes directed to pulp recovery systems,
which
through further equipment removes seeds and reject material. The clean
portion
of the pulp is pumped through heat exchangers, pasteurized, cooled and
chilled
by refrigeration. This product is packed in 40 Ib containers and stored
in
freeze rooms for future use.
Juice processing for pasteurized single strength
The canning of pasteurized
juice begins in Florida
in August and September and coincides with the harvesting of fruit for
the
fresh fruit market. Overflow from the packing houses is sent to
processing
plants, and some fruit is delivered directly from the groves. Blending
of fruit
varieties and control of ratios is usually accomplished by the fruit
storage
bin operator. Juice is pumped from finishing to process receiving tanks
that
are equipped with agitators to keep the pulp suspended. These tanks can
also be
used for adding sugar or other ingredients when canning sweetened or
fortified
juices. From the tanks the product is pasteurized by hot filling at 195
200ºF.
Peel oil enters the juice in
the extraction process.
Higher extraction pressures yield more juice but also force more peel
oil into
the juice stream. Too much oil gives off flavors to the juice and in
the early
days the amount of oil could be controlled by extractor pressure only.
Since
then de oilers have been developed as an integral part of the
pasteurizing
process.
In the de oiler the juice
temperature is elevated
above the can filling temperature. The juice is then flashed into a
vacuum
chamber controlled by a flash condenser and vacuum system to the can
filling
temperature. As a rule of thumb, a flash of 10ºF, say from 205 195ºF
will
remove approximately 1% of the mass as evaporated water vapors. This
flash
evaporation strips out some of the oil and the greater the difference
between
the heater and flash chamber, more evaporation occurs and more oil is
removed.
Since the oil has a higher boiling point than the juice, the removal of
oil is
an example of steam distillation or steam stripping. Some lower boiling
constituents in the juice, which contribute to the juice essence, are
also
removed in the de oiling process. This is not considered objectionable
in
processing hot pack canned products. The juice entering the can must be
hot
enough to pasteurize it (about 195ºF). However, there is a limiting
high
temperature for taste reasons which, therefore, limits the amount of
oil which
can be removed by flashing and has an influence on extractor pressure
settings.
Some de oilers use heat
exchangers to bring the
juice up to filling temperature and heat the juice further by direct
injection
of live steam. The condensing of steam adds water to the juice but in
the
vacuum chamber an equal amount of water is flashed off. It is the
authors
opinion that there is a danger of adding essence of boiler or essence
of steam
pipe to the juice with the use of this type of de oiler. An advanced
design
uses indirect heating only. The flash chamber is connected to a
stripping
condenser through which the water and oil vapors pass. The water phase
is
condensed and returned to the juice and the oil exits through a vent
line
connected from the condenser to an oil recovery system.
The heated juice is pumped
from the pasteurizer de
oiler to the can filler bowl, which has a
demand float that regulates the juice flow through the system. Can
fillers
rotate and accept empty cans through mechanical timing devices driven
by the
filler which space the cans to synchronize with the filler valves.
Under the
rotating filler bowl, the cans are lifted by cam action and forced
upward
toward the bottom of the bowl. The cans contact the valves located in
the bowl,
push the valve stems up, opening the valves and the hot juice flows by
gravity
into the cans.
Filled cans exit the filler
and enter the can closing
machine, which is driven by the filler and thus synchronized. A small
stream of
live steam is injected into the head space at the top of the can to
expel air
that would otherwise be trapped between the lid and the juice. Lids are
applied
and seamed and the cans exit the closer into a can twist, which inverts
them so
that the hot juice pasteurizes the lid.
The cans are then fed into a
water spray can cooler.
Cans enter the cooler at about 195ºF and exit the cooler at about
100°F. They
are stored in warehouses at ambient temperature.
Single strength orange juice
is also filled into
glass containers at 190 195ºF, after which they are cooled first by
warm water
to avoid thermal shock, followed by chilled water. The coolers in this
type of
operation carry the bottles on a wire mesh belt (as compared to the
spinning of
the cans) with recirculating water sprays in sections along the length
of the
cooler, the warmest water at the inlet end. The outlet section uses
chilled
water (about 35°F) and cools the product to around 50ºF after 1 h
residence
time in the cooler. This product is stored and distributed at cool
temperatures
and given a shorter shelf life than the canned product due to the
inevitable
colour and taste changes with age.
Juice processing for concentrate
The obvious advantages of
making concentrate from
fruit juices are: (1) reduced volumes for storage and shipping, and if
enough
water is removed from the juice, the concentrate can be kept at ambient
temperatures without spoiling. The most widely used technique is to
apply heat
to the product in order to evaporate water by boiling, though other
processes,
such as removing the water by freezing or ultra filtration have been
tried on
citrus juices without any wide acceptance.
Citrus juices are quite
sensitive to heat and if
exposed to elevated temperatures or even kept at ambient temperature
for too
long, flavor and color changes will occur. With high temperature short
time
(HTST) pasteurizers orange juice may be heated quickly to 185 200ºF.
held for
30s and quickly cooled without any color change. This process stops
enzymatic
reactions, which would otherwise cause cloud separation, flavor and
color
changes.
There is, however, a non
enzymatic reaction that
takes place in juice and concentrate that in time causes browning due
to sugars
reacting with proteins. This reaction is retarded at low temperatures.
For this
reason all orange juice concentrate produced for reconstitution into
juices is
stored at temperatures of 20ºF or lower. This allows for holding
inventories of
concentrate for more than 1 year if necessary.
The earliest orange
concentrate in Florida and
California was produced on steam driven evaporators, sometimes only
open
kettles. The concentrate produced was not suitable for juice, but was
used for
drink bases and confections. By 1935 several processors were producing
concentrate on vacuum evaporators designed by various equipment
manufacturers
originally for use on other products. These were medium to high
temperature
evaporators, which by todays standards produced an inferior product.
The concentrate
was then heated and hot filled into cans. The canned product was cooled
by
water spray and stored at ambient temperatures. The market for this
product was
in Europe and England and for the armed forces during World War II.
It was during the period
between 1935 and the middle
1940s that considerable research and development was done on producing
concentrate by using high vacuum low temperature evaporators. Research
and
development showed that by the use of a low temperature (below 160ºF)
concentration
process followed by frozen storage a much fresher tasting concentrate
could be
produced. The trade name for this product became Frozen Concentrate
Orange
Juice or FCOJ.
By 1950 equipment
manufacturers had successfully
developed commercial low temperature high vacuum evaporators, some of
which
used refrigeration heat pump designs and others, which used large
recompression
jets. Concentrate was pumped out at 58º Brix at temperatures around 55
60ºF.
Unpasteurized, single strength cut back juice was blended in to make
42º Brix
for canning, which partly compensated for the loss of volatiles in the
concentrate process.
The concentrate produced by
this low temperature
technique was of very good quality and was packed mostly in 6 oz cans,
which
were sent through a blast freezer and stored at –10ºF.
It became apparent after some
time that heat
treatment was necessary to stabilize the canned product, as frozen
storage
temperatures could not always be guaranteed after leaving the plant
refrigeration facilities. Microbial spoilage and/or cloud separation
due to
pectolytic enzyme action would sometimes occur. Around the mid 1950s,
high
temperature short time pasteu rizers were added to the concentrate
process
which would bring the temperature of the juice to around 195°F with
enough holding
time to kill the microorganisms and deactivate the pectin esterase.
1. Characteristics of 1950s
evaporators
To understand the
significance of the advance taken
by later designs, it is necessary to examine these first commercially
successful evaporators. These early low temperature evapo rators were
of the
recirculating type, shell and tube falling film design. Stainless steel
tubes
were installed vertically in, a configuration referred to as a tube
nest or evaporator
body. Juice entered the top of tubes and flowed downward as a film
against the
inside wall of the tubes. Evaporated vapors traveled downward through
the
center of the tubes and exited with the juice through a vapor liquid
separator.
The juice was pumped back to the top of the tube nest and into the
tubes
through some sort of distribution device. On the outside of the tubes,
referred
to as the shell side of the tube nest, steam condensed under vacuum
giving up
its heat to the boiling juice on the tube side of the tube nest.
Tube nests were arranged in
stages and effects and
each stage held a considerable amount of product. When the correct
concentration was reached in the final stage, concentrate was pumped
out and
replaced from earlier stages under liquid level control. Brix control
of the
product from these evaporators was good because of the large
stabilizing effect
of the bulk of product in process.
Maximum evaporator operating
temperatures varied
with manufacturers design, up to 120ºF for steam driven types with
recompression jets. Refrigeration heat pump evaporators highest process
temperature was around 75ºF (not including the pasteurizer).
These evaporators required
considerable heat
transfer surface because of low temperature difference across the tube
walls
and because of high resistance to heat transfer caused by cold thick
product
inside the tubes. Vapor liquid separators were large as were vapor
transfer
ducts by virtue of the large volume of the evaporated water vapors.
These large
spaces were almost impossible to clean in place (CIP) and after 30 40 h
of
operation the separator man ways and top distribution chambers needed
to be
opened and manually cleaned. Cleaning required a considerable amount of
down time
and man hours. Recharging these evaporators with juice, restarting and
reaching
steady operation at 58° Brix pump out, also added to loss of production
time.
2. Modern evaporators for
citrus fruit
The low temperature
evaporators had been designed on
the basis that low evaporation temperatures would compensate for the
long
residence time in the process and
avoid
heat damage. The successful use of high temperature short time
pasteurizers
demonstrated that no significant heat damage was done to the product
provided
the time of elevated temperatures was kept short.
This experience along with
the aforementioned
deficiencies of the low temperature evaporator design gave rise to the
development of the thermally accelerated short time evaporator (TASTE),
which
at the present time is used almost exclusively in the world wide citrus
industry. These evaporators are of the multi effect, multi stage,
single pass
design and the first one was installed in Florida in 1958.
For the reader who is not
familiar with evaporator
terminology it might do well here to explain the difference between the
evaporator effect and evaporator stage. Effect defines the heat flow
through an
evaporator, the first effect always the warmest which receives the
energy for
driving the evaporator. In refrigeration low temperature heat pump
evaporators,
which were usually double effect units, the first effect received heat
as the
condenser side of a refrigeration system. The water vapors from
evaporation
inside the tubes of the first effect traveled through vapor lines to
the shell
side of the second effect, condensed and gave up its heat to the
boiling liquid
inside the tubes of the second effect. The water evaporated in the
second
effect entered the shell side of a vapor condenser, condensed and
transferred
its heat to a boiling refrigerant inside the tubes. The refrigerant
vapors were
boosted by the compressors and the refrigeration condensing heat was
absorbed
by the first effect, completing the cycle.
The TASTE evaporator is
driven by boiler steam
directed to its first effect shell side. For each pound of steam
condensed, an
equal amount of water vapors are evaporated and sent to the next
(second)
effect, from the second to the third and so on, with the evaporated
vapors from
the last effect condensed by cool water, usually recirculated from a
cooling
tower.
The stages of an evaporator
define the product flow the
first stage receiving the single strength
feed juice. Any effect of an evaporator can be designed to receive feed
liquid.
A forward flow evaporator feeds the first effect and product flows
parallel
with the heat flow through the effects. Reverse flow feeds product to
the last
effect and pumps out of the first effect. Mixed flow loosely defines an
evaporator, which is staged as neither of the above.
The number of effects used
determines the energy
efficiency of the evaporator. A single effect steam driven evaporator
will
evaporate approximately one pound of water for each pound of boiler
steam
condensed. In a two effect unit, the first effect is the boiler for the
second,
thus two pounds of evaporation per pound of steam is achieved, and so
on. This
pound for pound ratio does not exactly apply to citrus evaporators as
it does
not include the heat required for preheating (heating the juice to the
first effect
temperature). Other forms of evaporator design have been offered to the
citrus
industry, such as the use of vapor recompression, in order to reduce
the steam
and/or energy requirements. However, the evaporation to steam ratio for
a seven
effect TASTE evaporator is 6.1/1. That is, 1 Ib of steam will cause 6.1
Ib of
evaporation (including the preheating load). This energy efficiency is
more
favorable than that achieved with recompression, especially when
considering
the greater capital investment for the recompression plant. Multi
effect steam
driven evaporators are much more forgiving to upsets caused by infeed
flow and
Brix variables and are thus easier to control. They may also be
operated at
lower than design capacities simply by throttling the steam valve.
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