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2002
Packaging soft drinks and reconstituted juices in beverage
cans
In recent years we have witnessed growing consumption of beer
and soft drink, both carbonated and noncarbonated, marketed in
cans.
This brochure introduces basic concepts and general information
on the manufacture of cans, raw materials, the production of
beverages, and quality control of these systems.
Caniel laboratory will be pleased to serve its customers and
provide them with information on any matter associated with the
issues covered in this bulletin.
The attached recommendations are up-to-date and replace any
previous recommendations on the subject These recommendations
should be seen as informative only Caniel is not responsible for
the results of following the guidelines and information contained
in this brochure
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1. The Can Manufacturing Process Two-piece cans (drawn cans) are
produced using a special technology that includes pressing the
medal into cups using a dies and then forming the cup into a can
using a process known as drawing and wall ironing.
The can is printed on the outside and coated on the inside. This
method guarantees that the can will be impermeable and able to
withstand standard manufacturing processes and corrosion.
basecoat: The basecoat protects the outside of the can and
provides background color for the printing system.
Inside coating (first coat): First coat is sprayed on the can in
order to create a protective layer between the metal and the
product during storage. The concave part of the bottom of the can
(on the outside) is coated, too, in order to prevent external
corrosion.
Inside coating (second coat): Second coat covers exposed spots
that were not covered by the first coat, so as to guarantee that
cans have a minimum of exposed metal.
Automatic equipment is installed on the production line to
inspect all the cans using a light tester that is extremely
sensitive to holes and leaks. Damaged cans are rejected too.
2. Packing
The cans are placed on pallets. Currently the pallets are 21
rows high. Each row contains 361 cans, for a total of 7,581 cans on
a pallet.
Because of the height of the pallet and the need to stabilize
it, it is held by a rigid metal frame, enclosed by four loops of
packing tape.
Stretch-wrap plastic isolates the cans and protects them from
the ambient environment.
Each pallet has a paper label that indicates the product name,
production code, and serial number. Reference should be made to
this label if there are any problems or failures.
Production date is printed on each can in a hidden form.
After unloading the cans, customers are requested to place the
frame back on the wooden pallet and to return them to Caniel.
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3. Productions and Filling with Carbonated Beverages
3.1 Empty-Can Conveyor
Because cans are delicate and lightweight, care must be taken in
every aspect of moving empty cans. Make sure that all passages are
very smooth to permit the ready flow of empty cans. The slops of
the filling lines should be moderate. Make sure that the conveyor
is always full of cans.
This will prevent unnecessary damage to cans.
The can-send system at the entrance to the filling machine must
grip the can. This method keeps cans from collapsing when they come
into contact with the can send.
3.2 Filling Machine (Filling Process)
Phase 1 Moderate pressure locks the can onto the fill head.
Phase 2 The actual filling stage, during which the can is locked
with a working
pressure that permits good filling
Balance the pressures in the filling system so as to avoid
exerting a force of more than 100 kg on a can.
The filling-base pressure should correspond to the equipment
manufacturers instructions and take account of the maximum
permissible load on a can.
To guarantee normal flow of cans at the entrance to the filling
machine and its exit make sure that:
3.2.1 The empty-can feed conveyor is 0.0250.050 mm above the
filling bases.
3.2.2 When the full cans are removed from the filling bases they
are about 0.0250.050 mm above the conveyor leading to the seaming
machine.
4. Seaming Machine
To ensure a proper seam make sure of the following:
4.1 Recommended system of rollers and seaming heads
4.2 Preventive adjustment should be carried out at least four
times a year and after every modification or refurbishing, in order
to guarantee proper seaming and keep cans from collapsing. During
the adjustment, check pin height (the weighted height between the
base plate at the end of the first action and the seaming
head),
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the base force exerted, and the gap between the first-operation
and second-operation rollers.
4.3 Strict adherence to recommended double seam dimensions as
stated in the information brochure, Recommended Seam Dimensions for
Aluminum End B64 206 on Caniel Steel Cans (see 21 below).
5. Full-Can Conveyor
After cans have been filled and seamed they should be flipped
over, so that the cover is on the bottom, and placed in the heater
in this orientation. Turning them upside down is very important for
detecting leaks. Most flaws in two-piece cans will be around the
easy-open end and seam.
Moving cans this 3 way ensures that leaks are detected during
heating process, with can rejected immediately by the fill-height
meter located right after it. To prevent unnecessary damage to the
seam, the cans should be turned right side up again immediately
after heating, so that the easy-open end faces up.
6. Storage (empty and filled cans)
The Cans must be stored in proper conditions and under
cover.
Make sure that cans are not exposed to direct sun (printed
colors fade in the sun), rain, high humidity, mechanical injuries
and blows, and inappropriate storage temperatures.
7. Storing filled Cans on Pallets
7.1 Make sure filled cans are packaged completely dried,
especially around the seam.
For shrink-wrapped packages, take special care that the cans are
completely dry before wrapping. Plastic shrink-wrap does not
breathe, so any water left on the cans cannot evaporate during
storage and will cause extremely rapid corrosion.
The use of perforated shrink-wrap is recommended, along with
high-pressure air nuzzles to remove any remaining water after the
cans have been cooled, or a final rinse with both de-ionized water
and air nuzzles.
Dents or scratches during storage may damage the printing and
the can and serve as a nucleus for corrosion.
Make sure the pallets are covered appropriately.
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Store the pallets with the cans on a flat and symmetrical
surface in order to keep the cans from collapsing.
7.2 High Humidity
High humidity may cause cans to sweat, producing corrosion on
the outside. Storage rooms close to production halls, must be
effectively insulated so that the steam and high humidity in the
latter will not cause external corrosion of the cans being
stored.
One must also provide appropriate airflow and ventilation,
especially in plants that are close to the sea, where there are
problems of high humidity and salt.
7.3 Storage Temperatures
Storage temperatures exceeding 3035, the result of exposure to
the sun in an unroofed place, accelerate the corrosion process and
shorten shelf life. In the case of filed cans, the increased
internal pressure, especially for highly carbonated beverages, such
as colas, lemon-lime drinks, soda, etc, will warp the ends.
8. Stress Corrosion of Easy-Open Aluminum ends
8.1 Easy-open ends on beverage cans are made of a Aluminum metal
that is coated on both sides. The most sensitive zone is around the
score, which is also the thinnest part of the end.
The main characteristic of this phenomenon is spontaneous
rupture of the end, causing the product to spill on other cans
packed on the same tray or pallet.
Later the process is apt to result in severe damage as a result
of secondary external corrosion of the can body.
8.2 Causes
The main cause of this phenomenon is an accumulation of moisture
and water left behind on the end by the filling process.
The moisture accelerates corrosion around the groove, which is
not protected by the coating. The groove is weakened and cracked,
after which the end bursts opens because of the internal
pressure.
Other factors accelerate this process, including:
8.2.1 A build-up of moisture as result of condensation of water
vapor from the air on the cans (extreme sweating)
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8.2.2 The exposure of the can to a corrosive environment on the
filling lines, such as excessive acidity of warmer.
9. Preventive Methods
The most important actions to prevent corrosion are as
follows:
9.1 Thoroughly rinsing the end of the can with clean water
immediately after seaming and again after it leaves the heater
(preferably with de-ionized water) to eliminate residues of
corrosion-promoting substances.
9.2 Completely drying the end surface before shrink-wrapping, by
forcing pressurized air through five nozzles for 10 seconds over
the entire surface of the end.
9.3 Make sure that the temperature of the can when it leaves the
heater is above the dew point, and preferably above 25C.
9.4 As noted in 7.3, storing the cans in a covered area, at a
temperature that does not exceed 30C35C.
Higher temperatures, resulting from exposure to the sun,
accelerate the corrosion process and may increase the pressure
inside the can, which in the case of highly carbonated beverages
may cause the end to burst.
10. More
10.1 Keep the heater water pH at the range 6.87.8; the
recommended range is a pH of 7.27.5.
A pH above 7.9 is considered corrosive. Alkaline water
accelerates external corrosion of aluminum end, causing the metal
to turn dark and damaging the printing on the outside.
10.2 Conveyor-belt lubricant recommended by Caniel, manufactured
by the German Henkel Corporation (dilute the soap 1:30 and apply it
using pumps and Henkel spray nozzles).
This is meant to avoid the use of soap that contains residues of
metals and/or other corrosion-promoting substances.
10.3 Avoid presence of corrosion-promoting equipment or parts,
made of brass or copper, near the can conveyors on the filling and
packaging line.
10.4 Leave spaces between the pallets in the finished-product
warehouse to permit better ventilation of the cans.
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Failure to follow these recommendations may lead to stress
corrosion accompanied by severe damage caused by secondary
corrosion on the outside of the cans.
11. Water Treatment
Treating the water serves the following objectives:
a. Guaranteeing uniform water composition throughout the year b.
Remove colloids and foreign matter from the water c. Remove
uncharacteristic colors d. Remove uncharacteristic flavors and
odors e. Reduce alkalinity f. Prevent microbial contamination
11.1 Standard Water Treatments
The most common method of treatment is with hydrated lime.
Adding this to alkaline water reduces alkalinity because dissolved
calcium and magnesium salts form insoluble precipitates.
Ca(HCO3)2 + Ca(OH)2 2 CaCO3 + 2 H2O Soluble insoluble
MgCO3 + Ca(OH)2 Mg(OH)2 + CaCO3 Soluble insoluble
If alkalinity comes from sodium carbonate, it is also necessary
to add calcium chloride.
Na2CO3 + CaCl2 CaCO3 + 2 NaCl insoluble soluble
11.2 Adding Coagulants
Coagulant treatment is meant to cause organic substances,
foreign matter, and calcium, magnesium, and sodium salts to
precipitate out; the iron salt forms a colloid to which these
materials adhere and precipitate from the solution.
The most common method is to add ferrous sulfate and calcium
hydroxide.
FeSO4 + Ca(OH)2 Fe(OH)2 + CaSO4
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11.3 Chlorination
Active chlorine must be added to the water to disinfect it and
remove all dissolved organic matter that might cause unpleasant
odors and aftertastes. The chemical process is as follows:
Cl2 + H2O HCl + HOCl oxidant
For effective oxidizing, the concentration of free chlorine,
expressed as Cl2, must be at least 0.6 mg (but no more than 2 ppm
to prevent corrosion), with a reaction time of more than 2
hours.
11.4 Filtration (sand and activated carbon)
Filtration with activated charcoal eliminates the chlorine left
from the chlorination process. Activated carbon catalyzes the
following reactions:
activated Cl2 + H2O 2 HCl + O
charcoal
At the end of the process, sand filtration removes the
precipitates formed by the lime treatment and chlorination.
11.6 Ion Exchanger
11.6.1 Whenever nitrate (NO3) concentration exceeds 10 ppm, an
anion exchanger or selective nitrate exchanger must be
installed.
O
CO2
act. charcoal
organic matter
Organic oxidation products
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11.6.2 Whenever iron concentration exceeds 0.1 ppm, cation
exchanger must be installed.
Another form of water treatment used by soft-drink industry is
reverse osmosis (RO), which can eliminate 90%95% of all dissolved
solids, such as carbonates, chlorides, and sulfates, and nearly
100% of dissolved organic substances with a molecular weight above
100, and of course total microbial filtration.
The method involves passing the water through cellulose acetate
or polyamide membranes.
The table illustrates the results of reverse osmosis
treatment:
Before R.O After R.O Totaled dissolved solids 205 < 50
Alkalinity 77 < 15 Chlorides 20 < 5 Total hardness 134
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Recommended Water Quality for Filling Cans
Parameter Max. recommended concentration, mg/L
Unit
1. Acidity 0 ---
2. Total alkalinity 50 CaCO3
3. Arsenic 0.01 As
4. Barium 1.0 Ba
5. Zinc 1.0 Zn
6. Chlorides 50 Cl
7*. Copper 0 Cu
8. Cyanides 0.01 CN-
9. Fluorides 0.8 F-
10. Hardness 200 CaCO3
11*. Iron 0.1 Fe
12. Lead 0.05 Pb
13. Manganese 0.05 Mn
14. Mercury 0 Hg
15. Nitrates 10 NO3
16. COD from KMnO4 4 hours at 27C Oxygen demand
17. Coliforms 0
18. Total count
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12. Soft drinks can be classified as follows:
B E V E R A G E S
Carbonated (CO2) noncarbonated
Natural/reconstituted Flavored drinks Natural/reconstituted
Flavored drinks
nonalcoholic alcoholic alcoholic nonalcoholic alcoholic
alcoholic (natural) (added) (natural) (added)
12.1 Hot-Filling
Hot-filling stages:
a. Filling with juice at a temperature of up to 92C b. Injection
of liquid nitrogen c. Seaming d. Cooling
The system is based on hot filling and developing positive
pressure by injecting liquid nitrogen into the headspace of the
can. The liquid nitrogen is injected before the can is seamed.
The nitrogen vaporizes after seaming, creating internal
pressure, which is necessary to keep the cans from collapsing after
cooling.
This method produces juices or beverages with positive pressure
in the can. Because the volume ratio of liquid to gaseous nitrogen
is 1:690, it take only a very small amount of liquid nitrogen to do
the job.
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The wrong amount of nitrogen may cause one of the following:
a. Excessive pressure, buckling of the end or bottom b. Low
pressure cans are sensitive to blows, producing creases and cracks
in the
inner coating and then corrosion.
The internal pressure at 25C should not be less than 1.3
bar.
12.2 Cold-Filling
Cold filling involves the following stages:
12.2.1 Cold-filling with juice at a temperature of up to 25C
12.2.2 Injection of liquid or gaseous nitrogen and seaming,
preserving the low oxygen level in the headspace. If gaseous
nitrogen is used, it does not provide any reinforcement to the
can.
12.2.3 Pasteurization and chilling (in this method, the
pasteurization temperature must be defined for each type of
beverage). During pasteurization or cooling make sure to use
low-alkaline and chloride- sulfate-free water.
During pasteurization and cooling the pH of the water should be
6.87.8, and preferably 7.27.5. A pH above 7.9 is considered to be
corrosive.
Alkaline water accelerates external corrosion of the aluminum
end and may damage the printing. The disadvantage of this method is
the long pasteurization time, which detracts from the organoleptic
qualities of the product. If gaseous nitrogen is used the can will
have relatively low mechanical strength.
Blows to the sides of the can may impair the quality of the
inner coating and accelerate internal corrosion.
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13. Raw Materials
13.1 Water
Because water is the main ingredient in beverages and
constitutes about 86% of the finished product, the water must be of
extremely high quality, clear, without turbidity, odorless, and
tasteless.
The level of dissolved minerals should be minimal, especial with
regard to nitrates. Nitrates should not exceed 10 milligrams a
liter; iron should not exceed 0.1 milligrams per liter; sulfur
dioxide should not exceed 5 milligrams per liter. Minimum levels of
chloride, sulfates, and dissolved air are also important.
13.2 Acidulants
Acidulants in beverages serve three purposes:
a. They give the drink its characteristic sour taste. b. The cut
the sweetness of the sugar. c. They serve as a preservative.
The most common acidulants in use are citric acid for
fruit-based drinks, phosphoric acid for colas, tartaric acid for
grape juice. The acid in beer and in natural or reconstituted
juices is natural, the result of the fermentation process (beer) or
the properties of the raw material (juices).
13.3 Antioxidants
Antioxidants such as ascorbic acid are added to some drinks.
Their purpose is to react with oxygen and prevent oxidation of the
ingredients.
13.4 Carbon Dioxide (CO2)
This gas is added to beverages during the carbonation process
(carbonated beverages only). Carbonation means saturating the
liquid with carbon dioxide, which gives the beverage a
characteristic flavor, serves as a preservative, prevents the
growth of bacteria, and slows the rate of corrosion in the can.
High-quality gas (low sulfur level) is important. The amount of CO2
in the product is expressed as volumes of CO2.
On this basis, carbonated beverages can be divided into three
groups:
a. CO2 volume greater than 3.5: colas, soda, tonic, ginger ale
b. CO2 volume 2.53.5: beer, lemon-lime drinks, orange drink c. CO2
volume 1.0-2.5: apple juice, grape juice, strawberry, raspberry
The CO2 volume is the ratio between the volume of the gas and
the volume of liquid.
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The upper limit for carbonation volume is 4. The internal
pressure at 21C must never exceed 60 PSIg.
13.5 Flavorings
Flavorings are the ingredients added to the beverage that give
it its characteristic taste. Food coloring, acidulants, and
preservatives are usually added as well.
Flavorings can be classified as follows:
a. Alcoholic extracts b. Nonalcoholic extracts c. Concentrates
d. Natural juice concentrates e. Emulsions f. Flavored syrups
13.6 Food coloring
Food colorings are supplied in the form of powder, paste, or
liquid.
13.7 Preservatives
Preservatives are meant to prevent spoilage caused by microbial
growth. The most common preservative is sodium benzoate, which is
tasteless and odorless at the appropriate concentrations and
effective against the growth of mold, fungus, and bacteria. The
recommended concentration is 150200 ppm. It is effective in sour
products (the non-ionized form is the active form).
Preservatives should not be added to products, like cider and
beer, that are pasteurized to kill bacteria.
13.8 Sweeteners
Most sweeteners are sugar-based products that provide sweetness
and add flavor and calories to the beverage. There are also
artificial sweeteners for diet drinks.
The most common sweeteners in use are as follows:
a. Crystalline sugar/sucrose b. Glucose c. Sugar syrup d.
Dextrose e. Sorbitol f. Artificial sweeteners
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For canned beverages, all these sweeteners must be totally free
of sulfur dioxide.
14. Carbonated Drinks: Production and Filling
The manufacturing and filling processes for carbonated beverages
must take account of the shelf life of canned drinks.
Soft drinks, unlike other canned food products, are extremely
corrosive. This generally causes iron from the walls and bottom of
the can to be dissolved by the product. A high iron-ion
concentration in the beverage (more than a few milligrams per
liter) may give some products an aftertaste. So care must be taken
during the production, filling, and seaming processes to assure the
following: a negligible concentration of iron ions in the raw
materials, removal of corrosion-promoting substances such as
nitrates and sulfur dioxide from raw materials and azo dyes from
the ingredients added, and minimal oxygen in the product and
headspace during the manufacturing process.
Handle the cans Carefully, without collisions that might damage
the special coating of the can.
Storage of both empty and full cans in an appropriate atmosphere
and temperature.
14.1 Preparing the Syrup
a. Preparing the beverage ingredients, such as acidulants,
flavorings and aromatic ingredients, and preservatives by
continuous mixing with water
b. Preparing the sugar syrup by mixing crystalline sugar
(sucrose) with water It is important to use sugar that is 99.9
percent pure to avoid aftertastes, heavy-
metal contamination, etc.
c. Mixing the two syrups together to create the final syrup,
which has a concentration of 5060 Bx.
Make sure that the mixing vats are made of stainless steel and
that the syrup and water never come into contact with iron pipes or
containers.
The acidulants in common use bind iron ions relatively easily
and may therefore cause primary contamination of the beverage with
iron ions, which has far-reaching implications for creating a
strong aftertaste and shortening the shelf life of the
beverage.
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14.2 De-aeration
In order to reduce the amount of air in the beverage to a
minimum, to inhibit the rate of corrosion and increase the shelf
life of the canned beverage, the water needs to be de-aerated
before the beverage is prepared.
Applying a strong vacuum to a vat while water is sprayed through
it.
Another method has been developed recently, in which pressurized
water is sprayed into a vat containing CO2. The gas removes the air
from the water, leaving a final concentration of air in the water
of about 0.50.8 ml by volume per 330 cc of beverage.
14.3 Carbonation
There are several ways to carbonate beverage. Most of them are
based on mixing the syrup and water in fixed ratios, depending on
the type of beverage, then chilling the product to nearly 0C and
injecting CO2 (see Figure 2).
The amount of CO2 injected into the beverage depends on several
factors:
14.3.1 The contact surface between gas and liquid: the larger
its area, the greater the efficiency of absorption
14.3.2 The contact time between the gas and liquid
14.3.3 The absolute pressure of the gas-liquid system
Water Syrup
Mixer
Cooler
Filler Can
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14.3.4 The temperature of the liquid: the colder the liquid, the
greater the solubility of gas in it
14.3.5 The type of product: products with a higher sugar level
can dissolve less CO2 than products with less sugar
14.3.6 The purity of the CO2: any contamination by another gas
and especially air will cause displacement of the CO2 (for example,
one volume of dissolved air in the beverage will displace 50
volumes of CO2)
At the end of the carbonation process the temperature of the
product must be 0C2C. This temperature will preserve the desired
carbonation level until filling and seaming.
14.4 Moving and Rinsing Empty Cans
When empty cans are being moved on the conveyor, make sure that
they do not bump against one another and are not damaged by the
conveyor equipment.
Mechanical impact can damage the coating and expose the
underlying metal; thereby increasing the rate of corrosion while
the product is being stored. Before the filling stage, the cans
should be rinsed in cold water and turned upside down during or
after rinsing. To maintain a low filling and seaming temperature,
avoid rinsing in hot water or steam. Be careful to remove residues
of the rinse water and any foreign objects from the can.
14.5 Filling Process
For carbonated beverages, the cans must be filled at a
temperature below 4C. Hence the carbon cooler should be close to
the filling unit and the pipe between the two units should be
properly insulated.
This will preserve the appropriate level of carbonation for the
beverage and reduce the risk of foaming when the can emerges from
the filling machine.
14.6 Foam Breaker
Highly carbonated beverages, such as colas, lemon-lime drinks,
and drinks with a large amount of dissolved air, are liable to foam
after filling when the canned is released to atmospheric pressure.
Because the foaming creates an emulsion of air and product, there
is a danger that this air will be trapped inside the can when the
canned is seamed. To avoid this, a unit is installed right before
the cans enter the seaming machine to inject CO2 into the headspace
of the can, so as to break up the bubbles and eliminate the trapped
air. Seaming machines for soft drinks are equipped with a
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device for spraying CO2 into the headspace so as to eliminate
the air trapped in it. The foam breaker mentioned above is one such
device.
Another device, located close to every seaming head in the
seaming machine, forces the air out of the headspace during the
actual seaming process.
The maximum permissible amount of air in a can at the
post-seaming inspection is 2 ml of air in the headspace and one ml
of air absorbed or dissolved in the product.
15. Heating or Pasteurizing Cans
15.1 Heating Carbonated Soft Drinks
Carbonated soft drinks that are filled at a low temperature must
be heated to raise the temperature of the beverage to the ambient
temperature for that season. This is necessary to prevent sweating
caused by the condensation of water vapor from the air onto the
outside of the cold canned.
In summer the cans should be warmed to 30C; in winter, to
20C25C.
This step must be carried out efficiently and carefully.
Inefficient heating will cause condensation of water vapor on the
outside of the can and speed up external corrosion processes.
Temperature above 30C for highly carbonated beverages such as
colas, lemon-lime drinks, and soda will create high pressure inside
the can and may warp the cover if the pressure exceeds 6
atmospheres.
The process involves spraying hot water, passing through a hot
water warmer, or passing through a steam channel.
15.2 Pasteurizing Carbonated Natural and Reconstituted
Beverages
Because they are marketed without preservatives, beverages such
as cider and beer must be pasteurized. The pasteurization
temperature ranges from 60C to 70C, and the time varies, both of
them as a function of the product type and composition. Because the
pasteurization temperature is high, insure a low carbonation level
and large headspace, to avoid attaining a pressure of 6 atmospheres
during the pasteurization process.
When pasteurization or heating is over, air must be blown on the
cans, while turning them over, in order to dry them completely
before packaging.
Cans that are still wet when they reach the packing trays will
cause external corrosion and rust during storage.
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16. Inspection of Filled Cans
After the pasteurization stage and before the packaging stage
the filled cans must be inspected in order to guarantee their
quality at the time of packaging and to detect any flaws that
caused leaks during the filling process. The standard filling
inspection is done using x-rays detector.
If the fill height is less than the calibrated range the canned
is rejected automatically.
This method rejects cans that were not properly seamed and
remained without ends.
Another but less common method is to weigh the cans. The
disadvantage is the need to calibrate the sensor for each different
type of beverage, because each drink has its own specific
gravity.
17. Production Code Marking
The production code is marked on cans, before filling process or
before packing.
There are several standard methods:
Contact methods
1. Printing a visible code on the side or bottom of the can 2.
Printing an invisible (UV) code
Non-contact methods
1. Laser engraving 2. Inkjet printing, usually on the bottom of
the can
18. Packing
The standard package is 24 cans in a tray with or without
shrink-wrap. Cans must be absolutely dry when packed. Damps cans
are liable to rust during storage, especially when packed in
shrink-wrapped trays, which create a closed corrosive cell if the
cans are still wet or damp.
19. Storage
Cans should be stored on a flat and symmetrical horizontal
surface. An uneven surface may cause the cans to collapse.
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20. Quality Control during the Manufacturing Process
The parameters that determine the shelf life of the product must
be applied during the filling process, along with strict attention
to appropriate recording to permit product tracking.
20.1 Filling Tests
Check the uniformity of the fill volume of the filling-machine
heads at the start of each production day. To do this, take a can
from each fill head and check its weight or volume. The deviation
among the fill heads should not exceed 5 ml; the minimum fill
volume is 330 ml. specific gravity of the beverage must be taken
into account.
20.2 Testing for Air in the Headspace and in the Beverage
This test is performed using a Zahm and Nagel device (Figure 2).
To run it, fill the glass burette (No. 1) with a solution of
20%30%. potassium hydroxide or sodium hydroxide. Place the canned
on the stand (No. 5) and lower the piercing unit (No. 21) into the
can, with the valve (No. 30) closed. Ignore the pressure reading on
pressure gauge.
Open the valve (No. 30) until the pressure on the gauge falls to
zero. Shake the device and the glass burette well until the soda
takes up all of the CO2, the volume of the trapped air bubble
remains constant, and the pressure-gauge reading is steady. Use
this reading to calculate the carbonation. The bubble of air
trapped in the burette after the valve is opened corresponds to the
amount of air in the headspace.
Continue opening the valve (No. 30) and shaking the can until
the pressure drops below 0.5 atmospheres. The amount of air added
to the original volume of the bubble indicates how much air was
absorbed by the product.
This test should be run once an hour, on one can from each fill
head after the heating stage.
The maximum amount of air in the headspace should be 2 ml; air
absorbed by the product should not exceed one ml. More than 2 ml of
air in the headspace indicates improper removal of air from the
headspace by the CO2 injection system, in the seaming and defoaming
stages.
Too much air in the product is the result of inefficient removal
or nonremoval of air by de-aeration of the water.
To check the efficiency of the CO2 injection when the can is
seamed, take a can from each seaming head, fill them with 330 ml of
saturated saline solution, and seam them.
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The air measurement device will indicate the amount of air
trapped in the headspace. If this exceeds 2 ml, regulate the flow
of CO2 during injection and repeat the test.
Remember that the CO2 flow must be laminar. A turbulent flow is
apt to cause precisely the opposite phenomenon, namely the
introduction of air into the headspace instead of its removal.
20.3 Fill-Temperature Test
The appropriate fill temperature is between 0 and 4C. This value
is important, because higher fill temperatures mean an increased
tendency to foam, which carries a risk of underfilling and
infiltration of air. The temperature should be checked every 30
minutes.
20.4 Carbonation Test
The carbonation is tested along with air by reading the maximum
pressure after the can has been shaken once and comparing it to the
pressure in the can after the air has been removed. The temperature
of the beverage yields the carbonation value, expressed as CO2
volumes, which is the ratio between the volume of CO2 gas and the
volume of beverage.
20.5 Testing the Temperature at the waemer Exit
To prevent condensation of water on the sides of the can, it is
important that it leave the warmer at a temperature higher than the
ambient temperature for the season.
In summer, the temperature should be a maximum of 30C; in
winter, 20C25C. Make sure that the temperature does not exceed
30C.
In highly carbonated beverages such as colas and lemon-lime
drinks, high temperatures may produce an internal pressure > 6
atmospheres, which could cause warping of the aluminum end.
Run this test on two or three cans every hour.
20.6 Checking the Calibration of the Weight Gauge or Fill-Height
Gauge
To do this, prepare standard cans filled with volumes of 330 ml,
325 ml, and 335 mm, and run them through these gauges. The can with
a fill volume of 325 ml should be rejected, while the other two
should pass. Run this test two or three times every shift.
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20.7 Checking for the Presence of the Code
Two or three times every shift one should take a can off the
line and check whether the code can be read for identification
purposes, as required by Israeli standard 1145.
20.8 Seaming Tests
Attaching the end to the can is a mechanical operation that
involves the rotational motion of a set of cylinders that produce
the double seam.
1. Actual overlap 2. Body hook 3. cover hook 4. Seam length 5.
Seam thickness (including free space) 6. Depth of depression
21. Seaming Test
The seaming test is usually divided into two types:
a. Destructive test b. Visual test
A. Destructive test
The destructive test is run at the start and in the middle of
each shift. For each test a can is taken from each head of the
seaming machine and three points along the end seam are tested.
The parameters listed in 20.8 above are measured manually, using
computerized systems such as Seametal.
Correct seam thickness is of utmost importance to prevent gas
lose and corrosion inside the double seam.
The maximum recommended seam thickness is three times the
thickness of the metal plus twice the thickness of the body metal
plus 0.006.
In case of deviations from the recommended dimensions, but the
overlap, seam thickness, and flange are acceptable, the seam will
be considered to be acceptable.
See the information bulletin, Recommended Seam Dimensions for
Aluminum End B64 206 on Caniel Steel Cans.
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B. Visual check
A visual check should be performed once an hour, by feeling the
seam and inspecting its soundness by eye, looking for cutover,
beads, or general damage.
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Appendix A Manufacture of Carbonated Soft Drinks
Cans
deplletizer
Rinser
Filling machine
foam breaker
Injection of CO2 during
closure
Closing machine
warmer and dryer breaker
Full-height gauge or
scale
Code printer
Packing machine
Palletizer machine
Crystalline Sugar
Sugar Solution
Filtration
Concentrated Syrup
Dosing
De-aerator Cardboard Trays
Shrink- Wrap
Warehouse for canned
carbonated beverages
Treated Water
Water treatment and
filtration
Raw Water
CARBO COOLER
Acidulates / Flavors /
Preservatives
Additives
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Appendix B