Principles of food preservation

1. FOOD PRESERVATION
BASIC PRINCIPLES OF PRESERVATION
METHODS OF FOOD PRESERVATION
Dr. M. Sonia Angeline
Assistant Professor
Department of Life Sciences

2. INTRODUCTION
• Food preservation is also targeted towards reduction of discoloration of food products by
enzymatic browning which occurs during preparation of processed food products.
• Preservation of food is aimed towards prevention and control of growth of spoilage
microorganisms and bacteria including fungi and yeasts and also reducing the rancidity
due to oxidation of lipids.

3. BASIC PRINCIPLES OF PRESERVATION
• The main objectives of food processing on a home scale, institutional scale, or
in the food industry are similar. They include –
• Removal of unwanted matter from food – unwanted matters may be inedible,
indigestible or harmful to health, such as husk from grain, the skin of some
vegetables, coconut shells, etc.
• The unwanted matter has to be removed by a different process including
shelling, milling, peeling etc.

4. BASIC PRINCIPLES OF PRESERVATION
• Making food safe for consumption – Some food contains natural toxins which need
to be inactivated, i.e., trypsin inhibitor in soya bean, fungal toxin such as aflatoxin
in groundnut & grains, infected portions of food materials, green portion of potato is
removed by visual examination, & chemical toxin & poison are discarded.
• Ensure the safety of food by using a process to remove toxins & heat to develop
microorganism& their toxins.
• Safe processing prevents contamination.

5. BASIC PRINCIPLES OF PRESERVATION
• Increased digestibility – most foods are difficult to digest unless they are cooked.
• Cooking softens fiber, gelatinized starch, denatures protein, & makes food easier to digest.
• Foods need special kind of processing for preservation.
• Enhance flavor color & taste – The acceptability of food depends on its organoleptic
qualities.
• Processing techniques enhance the appearance of food & many techniques make food more
tasteful.
• The browning crust is formed due to Miller reaction which gives bakery items its baked
flavor aroma & taste.
• Processing such as caramelization; fermentation etc gives food a different flavor.

6. BASIC PRINCIPLES OF PRESERVATION
• Improving texture & consistency – Processes such as emulsification, gel
formation & increase in viscosity are aimed to improve the texture &consistency
of ready to eat food.
• Minimized nutrients loss – Nutrition is better retained by controlled processing
conditions such as autoclaving, freezer drying & controlled heat.
• Nutrients loss due to processing is managed by adding extra vitamins.
• Processed margarine, butter, etc are fortified by vitamins.
• Other processed food often enriched with vitamins, minerals & lysine.

7. BASIC PRINCIPLES OF PRESERVATION
• Extending the self-life – Processing extends the self-life because apart from
removing unwanted, spoilt,& harmful matter & subjecting the food to
temperatures outside the danger zone, all processes such as dehydration, cold
storage, canning & pasteurization are aimed at preservation to food.
• Increased acceptability through fabricated foods – New products of uniform sizes
& shape are been introduced in the market.
• They are made from low- grade commodities which are plentiful or good for health.

8. BASIC PRINCIPLES OF PRESERVATION
• Removal of micro-organisms or inactivating them- This is done by removing air,
water (moisture), lowering or increasing temperature, increasing the concentration
of salt or sugar or acid in foods.
• If you want to preserve green leafy vegetables, you have to remove the water from
the leaves so that micro organisms cannot survive.
• You do this by drying the green leaves till all the moisture evaporates.

9. BASIC PRINCIPLES OF PRESERVATION
• Inactivating enzymes- Enzymes found in foods can be inactivated by changing
their conditions such as temperature and moisture, when you preserve peas, one
of the methods of preservations is to put them for a few minutes in boiling water.
• This method also known as blanching inactivates enzymes and thus, helps in
preserving the food.
• Removal of insects, worms and rats: By storing foods in dry, air tight containers
the insects, worms or rats are prevented from destroying it.

11. PRINCIPLE OF FOOD PRESERVATION
• The basic principle of food preservation includes:
• Preservation or delay of microbial decomposition: That is archived by :
• Keeping out microorganisms (asepsis)
• Removal of microorganisms, i.e., by filtration
• Hindering the growth of activity of microorganisms, i.e., by low temperature, drying,
anaerobic conditions, &
• Killing the microorganisms, i.e., by heat or radiations.
• Preservation or delay by self – decomposition of food. This is brought about by :
• Destruction or inactivation of food enzymes i.e, by blanching&
• Preservation or delay of chemical reactions i.e, preservation of oxidation by means of
an antioxidant.
• Preservation of damage caused by insects, animals & mechanical causes.

12. METHODS OF FOOD PRESERVATION
• Preservation of food is achieved by application of physical, chemical and/or biological
methods are as follows:
• A good method of food preservation is one that slows down or prevents altogether the
action of the agents of spoilage.
• Also, during the process of food preservation, the food should not be damaged.
• In order to achieve this, certain basic methods were applied on different types of foods.
• For example in earlier days, in very cold weather condition, ice was used to preserve
foods.
• Thus, very low temperature became an efficient method for preventing food spoilage.

13. METHODS OF FOOD PRESERVATION
• Physical methods
• Cooling to
→ Low temperature refrigeration (0 to 7°C) - preserves for shorter period (days) →
Freezing - preserves for several months
• Heating → pasteurization, cooking, sterilization etc
• Exposure to ionizing radiation → U.V., γ, etc
• Application of high pressure
• Drying → removal of water to a level which does not support the growth of
microorganism

14. METHODS OF FOOD PRESERVATION
• Chemical methods
• Quite often it is either impossible or undesirable to employ conventional physical
methods of the preservation.
• In such situation one has to opt for chemical methods of preservation.
• It involves application of chemical additives which act as antimicrobial agents.
• Biological methods
• Souring (fermentation) lactic and acetic acid, e.g. cheese and cultured milk.

15. METHODS OF FOOD PRESERVATION
• The principles of various methods for food preservation are as
1) Prevention or delay of microbial decomposition
• By keeping out microorganisms (asepsis)
• By removal of microorganisms
• By hindering the growth and activity of microorganisms (e.g. by low temperatures,
drying, anaerobic conditions, or chemicals)
• By killing the microorganisms (e.g. by heat or radiation)
2) Prevention or delay of self-decomposition of the food
• By destruction or inactivation of food enzymes (by blanching)
• By prevention or delay of chemical reactions (By using antioxidant)

16. SEVERAL METHODS ARE AVAILABLE FOR
PRESERVATION OF FOOD BASED ON THE ABOVE
PRINCIPLES, THE METHOD INCLUDE:
• Preventing the accessibility of food to microorganism by asepsis and packaging
• Physical removal of microorganisms from food by filtration or centrifugation
• Hindering the growth and activity of microorganism by use of preservatives, use of low
temperatures atmospheric control in packaging and storing of foods and decreasing
water activity in foods by drying or evaporation
• Killing the microorganism by use of high temperature and ionizing radiation
• Inactivation of endogenous enzymes by moderate heating
• Inhibition of chemical reaction through the use of chemical additives
• Fermentation of foods to yield more stable or less perishable food product
• Food preservation as it is practiced in the industry always involves the use of
combination of methods for achieving maximum effectiveness.

17. METHODS OF FOOD PRESERVATION
• Asepsis or preventing the accessibility of food to microorganisms is well exemplified in
nature, the protective covering in natural foods such as skins on fruits and vegetables, shells
on eggs and nuts and skins and membranes on livestock and fish prevent the attack by
microorganisms and maintain the living tissues in healthy condition.
• Microbial attack is facilitated only after the death of the animal or when the skin is
physically damaged.
• Packaging of foods and food products in a variety of materials such as metal cans, plastic
films pouches, bags or boxes, paper bags or cartons and glass bottles provide effective
protection against microbial attack.
• Filtration or centrifugation is adopted to physically remove microorganisms particularly in
liquid foods such as milk, soft drinks, fruits juices and alcoholic beverages such as wine and
beer.