Question

4. Write any five methods used for food preservation. Also write how it works and
some examples of food that can be preserved by each method.

Answer 1

Answer:

canning boiling freezing baking pickling

Answer 2

Answer:

Canning

Drying

Pasteurization

Freezing

Blanching

Please mark Brainliest

Explanation:

Freezing is a means of preserving food through the application and maintenance of extreme cold temperature (−4°C to −40°C). It is effective because most of the water of the food tissue is changed from the liquid to the solid state. This change in the physical state of water retards enzy-matic action and stops microbial growth, the cause of food spoilage, thus preserving food. Many foods can be frozen for twelve months or more without major changes in size, shape, texture, colour and flavour.

Blanching (dipping the products in boil-ing water for two to three minutes) veg-etables before freezing reduces the num-ber of microorganisms, removes some air from the tissues, makes them more compact and enhances their colour. Its most important function is to inactivate enzymes otherwise that would cause dete-rioration in palatability, colour and ascor-bic acid content during storage.

Pasteurization is a heat treatment that kills part but not all the micro organisms pres-ent and involves the application of tem-peratures below 100°C. The heating, may be by means of steam, hot water, dry heat or electric currents and the products are cooled immediately after the heat treat-ment. Milk is usually pasteurized.

Pasteurized products are not ster-ile. They contain vegetative organisms and spores which are still capable of growth. Hence many pasteurized foods must be stored under refrigeration. Pasteurized milk can be stored for over a week under refrigeration while pasteurized milk stored at room temperature will spoil within a day.

Canning involves the application of tem-peratures to food that is high enough to destroy essentially all micro organisms present. It also involves airtight sealing in sterilized containers to prevent recontam-ination. The degree of heat and the length of time of heating vary with the type of food and the kinds of micro organisms. Large quantities of food are canned for preservation. In developed countries, canned foods form a major part of the diet of the people. Items often canned are meats and meat products, fruits and vege-tables, fish products, soups, etc.

Dehydration is the extraction of moisture from food products like fruits, vegetables, herbs and meat.  

 

It inhibits the growth of microorganisms and imparts a long stor-age life. This is a modern development of smoking and drying. Some changes that occur during the process of dehydra-tion are:

·        Chemical changes

 

·        Browning and flavour changes

 

·        Denaturation of proteins

 

·        Concentration on the surface of the food (case hardening)