• Refrigeration and
• Freezing.
Refrigeration
This Is also known as cold storage. The food is cooled to below 4°c. Spoilage is not prevented but slowed down. Meat and fish store well under refrigeration. Cold storage warehouses are used to store large supplies of fruits, butter, cheese and eggs for up to ten months. Most other foods can be stored for a few weeks. Home refrigerators preserve food for short periods.
Freezing
This is one of the most important methods of preserving food today. The frozen food is kept at below -18°C, there by preventing growth of micro organisms and greatly slowing down chemical changes. Under such low temperatures most foods can keep for more than a year.
Freezing does not destroy the nutritive content of food. Sometimes, certain process used in preparing food for freezing may cause some loss of vitamins. For example , vegetables are blanched by immersing them near boiling water before freezing. Blanching stops the enzymes in food from working and kills most micro organisms.
Packaging is important when we prepare food for freezing. Usually plastic or aluminium foil is used to completely seal the food inside containers. This packaging must prevent moisture loss from the food. Moisture loss will cause the frozen food to change colour, texture and flavour , and also lose its nutritive value.
