food preservation by refrigeration and air conditioning

Refrigeration and Air Conditioning Systems in Food Preservation

BY: AKSHAY PATHANIA

ASSISTANT PROFESSOR

MECHANICAL ENGINEERING DEPARTMENT

Food PreservationTHE FOOD PRESERVATION MAY BE DEFINED AS THE STATE IN WHICH FOOD MAYBE RETAINED OVER A PERIOD OF TIME WITHOUT BEING CONTAMINATED BYPATHOGENIC ORGANISMS OR CHEMICALS AND WITHOUT LOSING ITS COLOUR,TEXTURE, FLAVOR AND NUTRITION VALUE.

Food Preservation By R & ACApplications 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.

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

Methods of Food Preservation

1. Heat Processing

2. Dehydration

3. Chemical Preservation

4. Oils and spices

5. Canning

6. Pasteurization


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.


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.


Commercial Refrigerators for Food Preservation

Reach-in Refrigerators

These refrigerators are the most versatile and the mostwidely used of all commercial fixtures. These refrigeratorsmay be used for both storage and display of the product.When used for storage only, they have solid doors, while fordisplay of product, glazed doors are provided. Theserefrigerators are commonly used in grocery stores, meatmarkets, bakeries, lunch counters, restaurants and hotels.



Walk-in Cooler

The walk in coolers are mainly used as storage fixtures.They are available in a wide variety of sizes. These are usedby nearly all retail stores, markets, hotels, restaurants etc.for the storage of perishable foods. Some walk-in coolers areprovided with glazed reach-in doors for storing, displayingand dispensing of dairy products, eggs and beverages.



Display Cases

The principal function of display cases is todisplay the product or commodity in a mostattractive manner in order to simulate sales.Thus, in the design of a refrigerated displayfixture, the first consideration is given to theproduct being displayed.

a. Self service case

b. Service case


Cold Storage for Food Preservation

Many food products may be stored at sometemperature above freezing point. The storage may beshort term storage or long term storage. The storageswhich are used for short term storage purposes areknown as cold storages. The period for short termstorage ranges from one to two days or to a week ormore in some cases, but not more than 15 days underany circumstances. When perishable foods are to bestored for a longer period, they should be frozen andstored in frozen stores.


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


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.


Methods of Food FreezingI. 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)


Cold Storage Temperatures

food preservation by refrigeration and air conditioning

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