Aseptic packaging
Aseptic packaging is a method in which food is sterilized or commercially
sterilized outside of the can, usually in a continuous process, and then
aseptically placed in previously sterilized containers which are subsequently
sealed in an aseptic environment.
After cooling, the sterile food product is pumped to an aseptic packaging
system where the food is filled and hermetically sealed into previously
sterilized containers. Aseptically processed foods can be packaged in the
same types of containers used for retorted foods.
The sterilization agents available for aseptic packaging include heat,
chemical treatment with hydrogen peroxide and high energy irradiation (UV
light or ionizing (gamma) irradiation).
A combination of hydrogen peroxide and mild heat is most commonly used
with plastic and paperboard-based laminate packaging.
The most commercially successful form of aseptic packaging utilizes paper
and plastic materials which are sterilizes, formed, filled and sealed in
continuous operation.
The package may be sterilized with heat or combination of heat and
chemicals. In some cases, the disinfectant property of hydrogen peroxide
(H2O2) is combined with heated air or ultra violet light to make lower
temperatures effective in sterilizing these less heat resistant packaging
materials.
Aseptic packaging is also used with the metal cans as well as large plastic
and metal drums or large flexible pouches.
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This frequently requires packaging of such items as tomato paste or apricot
puree in large containers.
The food manufacturer then may use the tomato paste in the production of
ketchup or the apricot puree in bakery products. If such large volumes were
to be sterilized in drums, by the time the cold point reached sterilization
temperature the product nearer the drum walls would be excessively burned.
Such items can be quickly sterilized in efficient heat exchangers and
aseptically packaged.
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Modified Atmosphere Packaging
Modified atmosphere packaging (MAP) is a procedure which involves
replacing air inside a package with a predetermined mixture of gases prior to
sealing it.
Once the package is sealed, no further control is exercised over the
composition of the in-package atmosphere.
However, this composition may change during storage as a result of
respiration of the contents and/or solution of some of the gas in the product.
Vacuum packaging is a procedure in which air is drawn out of the package
prior to sealing but no other gases are introduced.
This technique has been used for many years for products such as cured
meats and cheese. It is not usually regarded as a form of MAP.
The gases involved in modified atmosphere packaging, as applied
commercially are carbon dioxide, nitrogen and oxygen.
Carbon dioxide reacts with water in the product to form carbonic acid which
lowers the pH of the food. It also inhibits the growth of certain
microorganisms, mainly moulds and some aerobic bacteria.
Lactic acid bacteria are resistant to the gas and may replace aerobic spoilage
bacteria in modified atmosphere packaged meat. Most yeasts are also
resistant to carbon dioxide.
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Anaerobic bacteria, including food poisoning organisms, are little affected
by carbon dioxide.
Consequently, there is a potential health hazard in MAP products from these
microorganisms.
Moulds and some gram negative, aerobic bacteria, such as Pseudomonas
spp, are inhibited by carbon dioxide concentrations in the range 5–50%. In
general, the higher the concentration of the gas, the greater is its inhibitory
power.
The inhibition of bacteria by carbon dioxide increases as the temperature
decreases.
Nitrogen has no direct effect on microorganisms or foods, other than to
replace oxygen, which can inhibit the oxidation of fats. As its solubility in
water is low, it is used as a bulking material to prevent the collapse of MAP
packages when the carbon dioxide dissolves in the food. This is also useful
in packages of sliced or ground food materials, such as cheese, which may
consolidate under vacuum.
Carbon monoxide (CO) will inhibit the growth of many bacteria, yeasts and
moulds, in concentrations as low as 1%. However, due to its toxicity and
explosive nature, it is not used commercially.
Sulphur dioxide (SO2) has been used to inhibit the growth of moulds and
bacteria in some soft fruits and fruit juices.
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Argon, helium, xenon and neon, have also been used in MAP of some foods.
MAP packages are either thermoformed trays with heat-sealed lids or
pouches.
With the exception of packages for fresh produce, these trays and pouches
need to be made of materials with low permeability to gases (CO2, N2, and
O2). Laminates are used, made of various combinations of polyester (PET),
polyvinylidene chloride (PVdC), polyethylene (PE) and polyamide.
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Modern Packaging System
Various terms for new packaging methods can be found in the literature,
such as active, smart, interactive, clever or intelligent packaging.
The definitions of active and intelligent packaging are:
● Active packaging changes the condition of the packed food to extend shelf
life or to improve safety or sensory properties, while maintaining the quality
of the packaged food.
● Intelligent packaging systems monitor the condition of packaged foods to
give information about the quality of the packaged food during transport and
storage.
Active packaging
Active packaging refers to the incorporation of certain additives into
packaging film or within packaging containers with the aim of maintaining
and extending product shelf life.
Packaging may be termed active when it performs some desired role in food
preservation other than providing an inert barrier to external conditions.
Active packaging includes additives or “freshness enhancers” that are
capable of scavenging oxygen, adsorbing carbon dioxide, moisture, ethylene
and/or flavor/odor taints, releasing ethanol, sorbates, antioxidants and/or
other preservatives and/or maintaining temperature control.
The following Table lists examples of active packaging systems, some of
which may offer extended shelf life opportunities for new categories of food
products.
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►The main active packaging systems are:
1. Oxygen scavenger:
The most common oxygen scavengers take the form of small sachets
containing various iron-based powders containing an assortment of catalysts.
These chemical systems often react with water supplied by the food to
produce a reactive hydrated metallic reducing agent that scavenges oxygen
within the food package and irreversibly converts it to a stable oxide.
The iron powder is separated from the food by keeping it in a small, highly
oxygen permeable sachet.
2. Carbon Dioxide Scavengers/Emitters
There are many commercial sachet and label devices that can be used to
either scavenge or emit carbon dioxide.
The use of carbon dioxide scavengers is particularly applicable for fresh
roasted or ground coffees that produce significant volumes of carbon
dioxide.
Fresh roasted or ground coffees cannot be left unpackaged since they absorb
moisture and oxygen and lose desirable volatile aromas and flavors.
3. Ethylene Scavengers
Ethylene (C2H4) is a plant hormone that accelerates the respiration rate and
subsequent senescence of horticultural products such as fruit, vegetables and
flowers.
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Many of the effects of ethylene are necessary, e.g. induction of flowering in
pineapples and colour development in citrus fruits, bananas and tomatoes,
but in most horticultural situations it is desirable to remove ethylene or to
suppress its effects.
4. Ethanol Emitters
The use of ethanol as an antimicrobial agent is well documented. It is
particularly effective against mould but can also inhibit the growth of yeasts
and bacteria. Ethanol can be sprayed directly onto food products just prior to
packaging.
The size and capacity of the ethanol-emitting sachet used depends on the
weight of food, aw of the food and the shelf life required.
5. Preservative Releasers
One most commonly used preservative releaser is a synthetic silver zeolite
that has been directly incorporated into food contact packaging film. The
purpose of the zeolite is apparently to allow slow release of antimicrobial
silver ions into the surface of food products.
Many other synthetic and naturally occurring preservatives have been
proposed and/or tested for antimicrobial activity in plastic and edible films.
These include organic acids, e.g. propionate, benzoate and sorbate,
bacteriocins, e.g. nisin„ spice and herb extracts, e.g. from rosemary, cloves,
horseradish, mustard, cinnamon and thyme, enzymes, e.g. peroxidase,
lysozyme and glucose oxidase, chelating agents, e.g. EDTA, inorganic acids,
e.g. sulphur dioxide and chlorine dioxide, and anti-fungal agents, e.g.
imazalil and benomyl.
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The major potential food applications for antimicrobial films include meats,
fish, bread, cheese, fruit and vegetables.
6. Moisture Absorbers
Excess moisture is a major cause of food spoilage. Soaking up moisture by
using various absorbers or desiccants is very effective at maintaining food
quality and extending shelf life by inhibiting microbial growth and moisture-
related degradation of texture and flavor.
Moisture absorber sachets for humidity control in packaged dried foods,
several companies manufacture moisture drip absorbent pads, sheets and
blankets for liquid water control in high aw foods such as meats, fish,
poultry, fruit and vegetables are available.
7. Flavour/Odor Adsorbers
The interaction of packaging with food flavors and aromas has long been
recognized, especially through the undesirable flavor scalping of desirable
food components.
Two types of taints amenable to removal by active packaging are amines,
which are formed from the breakdown of fish muscle proteins, and
Aldehydes that are formed from the autoxidation of fats and oils.
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Intelligent packaging
Intelligent packaging includes indicators to be used for quality control of
packed food. They can be so-called external indicators, i.e., indicators which
are attached outside the package (time temperature indicators), and so-called
internal indicators which are placed inside the package, either to the head-
space of the package or attached into the lid.
1. Time temperature indicator (TTI)
A time temperature indicator (TTI) can be defined as a simple device that
can give the idea about easily measurable, time-temperature dependent
change which affects full or partial temperature history of a food product to
which it is connected.
The principles of TTI operation are based on mechanical, chemical,
electrochemical, enzymatic or microbiological irreversible change.
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2. Gas indicators
Gas indicators give the information about the integrity of the gas
composition inside the package, helping to monitor the safety and quality of
products.
As the gas composition in the package headspace can easily change due to
leakages, permeation, or respiration of fresh foods, it is important to observe
its stability throughout the shelf-life.
Gas indicators are devices placed onto package, changing its color by either
a chemical or enzymatic reaction, usually giving information about the
presence or absence of oxygen or carbon dioxide.
For example, gas indicators that change their colors when detecting change
in gas composition, turn from its original pink color to blue or purple when
exposed to oxygen or carbon dioxide. When the level of gas reduces, the
color changes back to original.
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3. Freshness indicators
Two types of the changes can take place in the fresh food product i.e.
(i) Microbiological growth and metabolism resulting in pH changes,
formation of toxic compounds, off-odors, gas and slime formation.
(ii) Oxidation of lipids and pigments resulting in undesirable flavors,
formation of compounds with adverse biological reactions or discoloration.
A freshness indicator indicates directly the quality of the product. The
indication of microbiological quality is based on a reaction between the
indicator and the metabolites produced during growth of microorganisms in
the product.
An indicator that would show specifically the spoilage or the lack of
freshness of the product, in addition to temperature abuse or package leaks,
would be ideal for the quality control of packed products.
A freshness indicator indicates directly the quality of the product. The
indication of microbiological quality is based on a reaction between the
indicator and the metabolites produced during growth of microorganisms in
the product.
An indicator that would show specifically the spoilage or the lack of
freshness of the product, in addition to temperature abuse or package leaks,
would be ideal for the quality control of packed products.
4. Pathogen indicators
Commercially available Toxin Guard TM is a system to build polyethylene-
based packaging material, which is able to detect the presence of pathogenic
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bacteria with the aid of immobilized antibodies. As the analyte (toxin,
microorganism) is in contact with the material it will be bound first to a
specific, labelled antibody and then to a capturing antibody printed as a
certain pattern. The method could also be applied for the detection of
pesticide residues or proteins resulting from genetic modifications.
Barcodes are used for storing data on the package that can be read by an
optical scanner. For example, this helps to track the location of the product
throughout the supply chain. Most typically used barcodes consist of 12
digits with different sizes and numbers beneath them. This solution is widely
used but also has the disadvantage of providing limited information.
Radiofrequency identification (RFID) devices on the other hand are a type
of intelligent packaging system that uses radiofrequency electromagnetic
fields to transfer data from a microchipped tag with the aim of automating
the identification and tracing the product (Following Figure). This approach
allows to gather more information about the product in the label, giving
more specified overview about the product.
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In addition to previous intelligent packaging systems, sensors are also used
to provide information about the product, monitor the changes during
storage and track and locate the product throughout the chain. Sensors are
considered as devices which give continuous signals.
For example, biosensors give information about the physiological changes of
the product or the presence of different biological or chemical materials in
the packaging environment.
In instance, microbes such as Salmonella and E. coli can be detected by a
nanoporous silicon-based biosensor. Next to that, gas sensors give
quantitative information about the gas composition of the package.
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