Canning or bottling is a method of food preservation that involves placing foods in jars or containers and heating them to temperatures that destroy microorganisms. There are two safe canning methods - the boiling water bath method for high acid foods like fruits and pickles, and the pressure canner method for low acid foods like vegetables and meats, which reaches temperatures above boiling to kill deadly botulinum toxins. Canning prevents spoilage by driving out air from the jar and creating a vacuum seal to prevent reentry of microbes when the jar cools.

1. INTRODUCTION TO
FOOD PROCESSING INDUSTRY
Methods of food processing and
preservation
Mrs.A.Kanchchana
B.Sc in Agri (Hons), M.sc in ENS
Lecturer Gr II
Department of food technology
Sri Lanka German Training Institute

2. Why you need to process and preserve foods?

3. • The main aim of food preservation is to minimize the growth of
microorganisms during the storage period, thus promoting longer
shelf life and reduced hazard from eating the food.
• Food preservation is essential because it extends the length of
time during which the food is nutritionally viable and safe to eat.
• Most fresh fruits, vegetables and animal products spoil quickly
without refrigeration, dehydration or preservation.
• most popular and effective preserving techniques employ salt, sugar,
vinegar or brine.

4. • The preserving agents prevent bacteria, mold and other potentially harmful
organisms from growing on the food.
• Dry preserving techniques, such as packing food in salt, draws water out of
the food, making it an inhospitable environment for microorganisms.
• Wet-preserved foods undergo heat processing that kills microorganisms, and
the vacuum seal created by proper canning prevents life-sustaining oxygen
from entering the container.

5. • Most bacteria and fungal spores cannot live without oxygen and do not survive
prolonged immersion in boiling water.
• A notable exception is the bacterium Clostridium botulinum, which causes a
dangerous and potentially fatal disease called botulism.
• Clostridium botulinum is unusually hardy and thrives in anoxic environments;
oxygen is toxic to it.
• It also survives boiling temperatures that kill most other bacteria. However, it
cannot survive acidic environments such as pickle brine.

6. • Non-acidic preserves such as un pickled vegetables, soup stock and all wet
meat preserves do not contain sufficient acid to kill Clostridium botulinum.
• The only safe technique for making these preserves is to process the jars in a
pressure canner, which subjects them to temperatures much higher than
boiling water.

7. Preservation of food by any method is based on the following
principles:
(A)Prevention or delay of microbial decomposition
(i) By keeping out micro-organisms (asepsis)
• Nature provides protective coverings around the food in the form of shells of
nuts, die skins of fruits and vegetables, the shells of eggs, and the skin or fat on
meat or fish.
• These protective coverings act as a preservative factor,
thereby preventing or delaying microbial decomposition.
• Even in the food industry several aseptic methods are adopted to prevent the
contamination of foods during its processing.

8. • In the canning industry, the load of micro-organisms determines the
heat process necessary for the preservation of food. This is better
known as aseptic canning.
• In the dairy industry, the quality of milk is judged by its bacterial
content.
• Packaging of foods is also an application of asepsis.
• The coverings may range from simple wrappers to hermetically
sealed containers of canned foods.
• Polythene bags and moisture proof wrappings including heavy foil,
heavily mixed papers and cellophane are used.

10. (ii) By removal of micro-organisms
• Filtration is a method used for the complete removal of micro-
organisms and is successfully applied only to clear liquids such as
water, fruit juices, beer, soft drinks and wine.
• The filter used in this method is made of asbestos pads, unglazed
porcelain and similar materials.
• This filter is sterilised and made “bacteria proof” before being used as
a filtration device.
• The liquid is filtered by forcing it under pressure through the filter.

11. (iii) By hindering the growth and activity of micro-organisms
• This may be done by low temperature or drying or by providing
anaerobic conditions.
• When anaerobic (absence of oxygen) conditions are created, some
aerobic organisms die while the spores of others may survive but are
unable to multiply in the absence of oxygen.
• This principle is used as a preservative factor in canned and
packaged foods.

12. • Low temperature at which foods are preserved in cold storage slows
down and sometimes prevents bacterial activity.
• Drying of foods is a very effective method of avoiding spoilage of
food, since micro-organisms cannot flourish in the absence of
moisture.
• Certain chemicals like sodium benzoate and potassium meta bi-
sulphite may be used for preservation, but they should be used with
great care as an excess of any of them may result in poisoning.

13. (iv) By killing the micro-organisms using heat or radiation
• In this process gamma rays or high speed electrons are used to
destroy the micro-organisms.
• Both types of radiations are termed as ionized radiations.

14. (B) Prevention or delay of self decomposition of food
• This is done by destruction or inactivation of food enzymes by
blanching.
• The inactivation affects many plant enzymes which otherwise might
cause toughness and change in colour.
• All plant and animal tissues contain enzymes which are highly active
at room temperature and above.
• For each 10° C (19°F) raises in temperature the rate of the chemical
change doubles.

15. • Rancidity of fats is an excellent example of undesirable oxidation
and leads to the deterioration in flavour of foods that may contain
only small quantities of fat. Oxidation also leads to a loss of
ascorbic acid.
• Plant and animal tissue fibre is softened, the surfaces of cut non-
acid fruits are oxidised and become darkened as a result of enzyme
action, thereby changing the colour, texture and nutritive value.

16. • Before freezing (to prevent the growth of bacteria) fruits and
vegetables are blanched to inactivate the oxidative enzymes, Blanch-
ing is done with hot water or steam and the extent of treatment
applied varies with the kind of food being treated.
• The brief heat treatment is supposed to accomplish
-reduction of the number of micro-organisms on the food,
-enhancement of the green colour of vegetables such as peas and
spinach, and
-prevention of damage because of mechanical causes, insects
and animals.

17. Note:
BLANCHING
• Blanching is a process where vegetables are exposed to boiling
water or steam for a brief period and then rapidly placed in ice
water to prevent cooking.
• Blanching stops the food's enzyme action and destroys any
microorganisms present on the vegetables surface reducing your
risk of food poisoning

18. • Items of food can be damaged either by insects and animals or by
mishandling. Therefore, meticulous care should be exercised to
minimize any damage to the foods.
• The entire operation of preserving foods is divided into three stages
of careful handling:
I. Proper packaging
II. Quick and effective transportation
III. Providing good storage facilities, like silos for grains and cold
storages for fruits and vegetables.

20. METHODS OF FOODS PRESERVATION
Foods can be preserved by the following methods
(i) Canning or bottling
(ii) Salting or sugaring (osmotic dehydration)
(iii) Drying
(iv) Fermentation
(v) Cooling and freezing

21. What does canning do?

22. 1.Canning or bottling
Canning Basics for Preserving Food
• Canning is an important, safe method for preserving food if practiced
properly.
• The canning process involves placing foods in jars or similar
containers and heating them to a temperature that destroys micro-
organisms that cause food to spoil.
• During this heating process air is driven out of the jar and as it cools
a vacuum seal is formed.
• This vacuum seal prevents air from getting back into the product
bringing with it contaminating micro-organisms.

23. Safe Canning Methods
There are two safe ways of processing food,
a. The boiling water bath method
b. The pressure canner method
• The boiling water bath method is safe for tomatoes, fruits, jams,
jellies, pickles and other preserves.
• In this method, jars of food are heated completely covered with
boiling water (212°F at sea level) and cooked for a specified
amount of time

24. • Pressure canning is the only safe method of preserving vegetables,
meats, poultry and seafood.
• Jars of food are placed in 2 to 3 inches of water in
a special pressure cooker which is heated to
a temperature of at least 240° F.
• This temperature can only be reached using the pressure method.
• A microorganism called Clostridium botulinum is the main reason
why pressure processing is necessary.

25. • Though the bacterial cells are killed at boiling temperatures, they can form
spores that can withstand these temperatures.
• The spores grow well in low acid foods, in the absence of air, such as in canned
low acidic foods like meats and vegetables.
• When the spores begin to grow, they produce the deadly botulinum toxins
(poisons).

26. • The only way to destroy these spores is by pressure cooking the
food at a temperature of 240°F, or above, for a specified amount of
time depending on the type of food and altitude.
• Foods that are low acid have a pH of more than 4.6 and because of
the danger of botulism, they must be prepared in a pressure canner.
The low acidic foods include:
• Meats
• Seafood
• Poultry
• Dairy products
• All vegetables

27. • High acid foods have a pH of 4.6 or less and contain enough acid so
that the Clostridium botulinum spores can not grow and produce their
deadly toxin.
• High acidic foods can be safely canned using the boiling water bath
method.
The high acidic foods include:
• Fruits
• Properly pickled vegetables
• Certain foods like, tomatoes and figs, that have a pH value close to 4.6
need to have acid added to them in order to use the water bath method.
• This is accomplished by adding lemon juice of citric acid.

28. Note:
• Don’t confuse a pressure canner with a pressure cooker, which is
used to cook food quickly.
• A pressure cooker does not have adequate room for both the canning
jars and the water needed to create the right amount of pressure to
preserve foods.

29. Note:
• Older canning methods are unreliable and, for that reason, aren’t
used or recommended today for home-canning.
• Occasionally, these methods are “revived” as being faster and easier
than water-bath or pressure canning, but using other methods is like
playing Russian roulette with your food safety.
Water bath canning Pressure canning

30. II. Salting or Sugaring
• Salting - Salting preserves food by removing the moisture and
creating an environment unsuitable for microbial growth.
• Very few bacteria grow in high salt solutions, so simply adding a very
high amount of salt can be an effective method of preservation.
• Salting is one of the oldest known methods of food preservation.
• Natural sea salts abundant in the Mediterranean region were readily
available in ancient times and were used to preserve meat, fish,
vegetables, and even some fruit.
• The amount of salt alone needed to preserve food is extremely high
and therefore can be unpalatable.

31. • Therefore, salt is often used in combination with another method, like
dehydration or an acidic solution, to preserve food.
Examples of salt-preserved foods include:
• Hard salamis,
• Bacon,
• Salt pork,
• Fish,
• Olives
• Pickles
• Preserved lemons.

32. • Sugaring is a food preservation method similar to pickling.
• Sugaring is the process of desiccating a food by first dehydrating it,
then packing it with pure sugar.
• This sugar can be crystalline in the form of table or raw sugar, or it
can be a high sugar density liquid such as honey, syrup or molasses.
• The purpose of sugaring is to create an environment hostile to
microbial life and prevent food spoilage.

33. • Sugaring is commonly used to preserve fruits as well as vegetables such as
ginger.
• From time to time sugaring has also been used for non-food preservations.
• For example, honey was used as part of the mummification process in some
ancient Egyptian rites.

34. • A risk in sugaring is that sugar itself attracts moisture.
• Once a sufficient moisture level is reached, native yeast in the
environment will come out of dormancy and begin to ferment the
sugars into alcohol and carbon dioxide.
• This leads to the process of fermentation.
• Although fermentation can be used as a food preservation method, it
must be intentionally controlled, or the results will tend to be
unpleasant

35. III. Drying
• Food drying is one of the oldest methods of preserving food for later
use.
• It can either be an alternative to canning or freezing, or compliment
these methods.
• Drying foods is simple, safe and easy to learn.
• With modern food dehydrators, fruit leathers, banana chips and beef
jerky can all be dried year round at home.

36. How Drying Preserves Food?
• Drying removes the moisture from the food so bacteria, yeast and mold
cannot grow and spoil the food.
• Drying also slows down the action of enzymes (naturally occurring
substances which cause foods to ripen), but does not inactivate them.
• Because drying removes moisture, the food becomes smaller and lighter in
weight.
• When the food is ready for use, the water is added back, and the food returns
to its original shape.

37. • Foods can be dried in the sun, in an oven or in a food dehydrator by
using the right combination of warm temperatures, low humidity and
air current.
• In drying, warm temperatures cause the moisture to evaporate.
• Low humidity allows moisture to move quickly from the food to the
air.
• Air current speeds up drying by moving the surrounding moist air
away from the food.

38. IV. Fermentation
• Fermenting - Fermenting is another ancient technique of food
preservation that has remained popular to this day.
• The popularity is most likely attributed to the unique flavor that is
accrued through fermentation.
• Fermentation itself is a form of food spoilage, but when the
microorganisms are tightly controlled, it can produce desirable
effects and provide safeguards against harmful organisms.

39. • The bacteria or yeast used in the fermentation process produce acid as
a byproduct, which acts to prevents other, potentially harmful bacteria
from thriving.
• As an added bonus, many of the organisms used to ferment foods are
also healthy additions to the natural flora of the human
gastrointestinal tract.
• Both sauerkraut and kimchi are examples of the use of fermentation
to preserve cabbage

40. • Fermentation in food processing is the process of converting carbohydrates to
alcohol or organic acids using microorganisms yeasts or bacteria under
anaerobic conditions.
• Fermentation usually implies that the action of microorganisms is desired.
• The science of fermentation is known as zymology or zymurgy.
• The term fermentation sometimes refers specifically to the chemical conversion
of sugars into ethanol, producing alcoholic drinks such as wine, beer, and cider.

41. • However, similar processes take place in the leavening of bread (CO2 produced
by yeast activity), and in the preservation of sour foods with the production of
lactic acid, such as in sauerkraut and yogurt.
• Other widely consumed fermented foods include vinegar, olives, and cheese.
• More localized foods prepared by fermentation may also be based on beans,
grain, vegetables, fruit, honey, dairy products, fish, meat, or tea

42. V. Cooling and freezing
• Chilling and Freezing - Bacteria and yeast grow best at specific
temperatures, usually between 40-140ºF.
• By lowering the temperature below 40ºF their metabolic and
reproductive action is significantly slowed.
• While this may not actually kill the bacteria and yeast, it does slow
the spoilage process.

43. • Although freezing food has been used in colder climates for hundreds of years,
the expansion of electricity and home appliances in the early and mid-20th
century greatly expanded the use of freezing as a food preservation method