2. Food Preservation
THE FOOD PRESERVATION MAY BE DEFINED AS THE STATE IN WHICH FOOD MAY
BE RETAINED OVER A PERIOD OF TIME WITHOUT BEING CONTAMINATED BY
PATHOGENIC ORGANISMS OR CHEMICALS AND WITHOUT LOSING ITS COLOUR,
TEXTURE, FLAVOR AND NUTRITION VALUE.
3. Food Preservation By R & AC
Applications of Food Preservation
It adds variety to the food.
It increases the shelf life of food.
It increases the food supply
It decreases the wastage of food.
4. Causes of Food Spoilage
1. Spoilage due to physical changes.
2. Spoilage due to chemical changes.
Enzymes
Micro-organisms
Bacteria
Yeast
Moulds (fungus)
Food Preservation By R & AC
5. Methods of Food Preservation
1. Heat Processing
2. Dehydration
3. Chemical Preservation
4. Oils and spices
5. Canning
6. Pasteurization
Food Preservation By R & AC
6. Food Preservation by Refrigeration
The Refrigeration is the only means of preserving food in its original position.
The preservation of perishable foods by refrigeration involves the use of
low temperature as a means of eliminating the activity of spoilage agents.
It has been found that the growth of food destroying microorganisms
is much faster (about 100 times) at a temperature of 10°C than at 4°C.
This is enough to emphasize the use of refrigerators for preserving
fruits, vegetables, fish, meat, milk etc.
Food Preservation By R & AC
7. Domestic Refrigeration for Food Preservation
The main purpose of a domestic refrigerator is to provide a low temperature
for storage and distribution of foods and drinks.
The storage in domestic refrigerators is generally short term or temporary
storage.
These are small in size and vary in capacity from 0.1𝑚3
to 0.25𝑚3
.
The refrigerant used should preferably be non-toxic.
Generally, methyl chloride, R-12 and R-11 are used as refrigerants.
Food Preservation By R & AC
8. Commercial Refrigerators for Food
Preservation
Reach-in Refrigerators
These refrigerators are the most versatile and the most
widely used of all commercial fixtures. These refrigerators
may be used for both storage and display of the product.
When used for storage only, they have solid doors, while for
display of product, glazed doors are provided. These
refrigerators are commonly used in grocery stores, meat
markets, bakeries, lunch counters, restaurants and hotels.
Food Preservation By R & AC
9. Commercial Refrigerators for Food
Preservation
Walk-in Cooler
The walk in coolers are mainly used as storage fixtures.
They are available in a wide variety of sizes. These are used
by nearly all retail stores, markets, hotels, restaurants etc.
for the storage of perishable foods. Some walk-in coolers are
provided with glazed reach-in doors for storing, displaying
and dispensing of dairy products, eggs and beverages.
Food Preservation By R & AC
10. Commercial Refrigerators for Food
Preservation
Display Cases
The principal function of display cases is to
display the product or commodity in a most
attractive manner in order to simulate sales.
Thus, in the design of a refrigerated display
fixture, the first consideration is given to the
product being displayed.
a. Self service case
b. Service case
Food Preservation By R & AC
11. Cold Storage for Food Preservation
Many food products may be stored at some
temperature above freezing point. The storage may be
short term storage or long term storage. The storages
which are used for short term storage purposes are
known as cold storages. The period for short term
storage ranges from one to two days or to a week or
more in some cases, but not more than 15 days under
any circumstances. When perishable foods are to be
stored for a longer period, they should be frozen and
stored in frozen stores.
Food Preservation By R & AC
12. Considerations should be kept in mind while
storing the foods in cold storages
1. Storage Temperature
2. Relative humidity and air motion
3. Mixed Storage
4. Product chilling
Food Preservation By R & AC
13. Frozen storages for Food Preservation
• When the food products are to be preserved in its original fresh state for longer periods, then they
are usually frozen and stored approximately at -15°C or below.
• They differ from cold storages in their size and the temperature range.
• The high quality products in good condition should only be frozen.
• The meet products do not require any special processing before freezing. They are directly freezed
taking them into frozen storages after washing.
Food Preservation By R & AC
14. Methods of Food Freezing
I. Slow or Sharp Freezing (-17°C to -40°C, used for boxed poultry, fish, eggs in cans etc.)
II. Quick Freezing
a. Immersion freezing (for liquid products)
b. Indirect contact freezing
c. Air blast freezing (-17°C to -40°C, used for shrimp, fish fillets, pre-cooled products packed in small
packages)
Food Preservation By R & AC
