An Introduction to Pasteurization

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An Introduction to Pasteurization
Pasteurization (or pasteurisation) is a technique
that uses heat to kill microorganisms and
prolong the shelf life of food and beverages. The
heat is usually lower than the boiling point of
water (100 C or 212 F). Pasteurization destroys
or inactivates numerous microorganisms, however,
bacterial spores are not destroyed, hence it is
not a type of sterilisation. Pasteurization
extends the shelf life of food by inactivating
spoiling enzymes using heat.
Products That Are Frequently Pasteurized

• Pasteurization can be used on solids and liquids
  that are both packaged and unpackaged.
  Pasteurized items include the following
• Beer
• Food in a can
• Products derived from milk
• Eggs
• Juices from fruits
• Milk
• Nuts
• Syrup
• Wine

Pasteurizations Evolution
Pasteurization is named after Louis Pasteur, a
French chemist. In 1864, Pasteur devised a
method for killing bacteria and reducing acidity
in wine by heating it to 5060 C (122140 F)
before ageing it. However, the procedure had been
used to preserve wine in China since at least
1117 AD. Lazzaro Spallanzani, an Italian
scientist, demonstrated in 1768 that heating
meat broth to boiling and then sealing the
container preserved the broth from
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deteriorating. To preserve delicacies, French
chef Nicolas Appert sealed them in glass jars
and plunged them in boiling water (canning) in
1795. Peter Durand used a similar technique to
preserve foods in tin cans in 1810. While
Pasteurs procedure was used for wine and beer,
Franz von Soxhlet did not propose the
pasteurisation of milk until 1886. So, why is the
technique referred to as pasteurisation when it
was used prior to Pasteur? Pasteurs research
showed that particles in the air, rather than
pure air, caused food to rot, which is the most
plausible reason. Pasteurs studies implicated
microbes as the cause of deterioration and
disease, resulting in the Germ Theory of Disease.
Pasteurization and Its Effects
A pasteurizer is based on the principle where
heat kills most pathogens and inactivates
certain proteins, including food deterioration
enzymes. The particular procedure is determined
by the products nature. Liquids, for example,
are pasteurised as they pass through a pipe.
Heat can be applied directly to a container like
a beer bottle in a tunnel pasteursier or via a
heat exchanger in flow pasteuriser. The liquid is
then cooled. The temperature is controllered in
zones or phases, as well as their duration. The
residance time and temperatures be it in a
bottled or canned product in a tunnel pasteuriser
or the time in a continuous flow pasteuriser
required to be controlled for effective
pasturisation. After the food has been packaged
into a container, it can be processed using a
tunnel pasteurizer. To avoid shattering glass
containers, hot water is utilised to achieve the
necessary temperature and via stages is
progressived heated. Steam or hot water can be
used to clean plastic and metal containers while
processing through the pasteurizer.
Improving Food Safety
The purpose of early pasteurisation of wine and
beer was to improve flavour. Food safety is the
primary goal of canning and modern
pasteurisation. The impact on food safety has
been significant, notably in the case of milk.
Many other foods and beverages can benefit from
pasteurisation. Several bacteria, including
those that cause tuberculosis, diphtheria,
scarlet fever, brucellosis, Q-fever and food
poisoning from Salmonella, E. coli, and Listeria,
thrive in milk. Raw milk was lethal before it
was pasteurised. For example, between 1912 and
1937, nearly 65,000 people in England and Wales
died of tuberculosis ingesting raw milk.
Milk-related illnesses decreased considerably
after pasteurisation.
The Effects of Pasteurization on Food
Pasteurization minimises the risk of food
poisoning and prolongs the shelf life of food by
several days or weeks. However, it may impact on
food texture, flavour and nutritional content.
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Knowledge of the food chemistry and biology is
required to determine the real effects. Eg. it
may, raise vitamin A levels, lowers vitamin B2
levels and has an impact on several other
vitamins for which milk is not a key source of
nutrition. The colour difference between
pasteurised and unpasteurized milk is caused by
the homogenization phase before pasteurisation,
not by pasteurisation. Pasteurization of fruit
juice has little effect on colour, but it may
cause the loss of some fragrance compounds as
well as a reduction in vitamin C and carotene
levels (a form of vitamin A). Pasteurization of
vegetables induces tissue softening and
nutritional alterations. Some nutrients are
depleted, while others are replenished.
Modern Advances in Pasteurizer Technology
Pasteurization refers to any procedure that
disinfects food and inactivates spoilage enzymes
without appreciably reducing nutritional levels
in the current era. These processes can be both
non-thermal and thermal. High-pressure processing
(HPP or pascalization), microwave volumetric
heating (MVH) and pulsed electric field (PEF)
pasteurisation are examples of newer commercial
pasteurizer technologies. The main methods for
canned and bottled products are thermal tunnel
pasturisation, while flow for high volume
pasturisation like milk and beer kegs thermal
flow pasteursiers are efficiently often employed
as tunnel pasturisation is impractical. Reference
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pasteurization/ Sarom Global HQ Australia,
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