There are different methods of preserving foods. The method that is used depends on the nature of the food.
The Common Methods of foods preservation are:
A. DEHYDRATION- This Involves removing water or moisture from food. It includes:
i. Solar or Sun Drying: This is a very effective way of preserving vegetables, maize, beans, cassava chips, yam chips, pepper, tomatoes, etc.
ii. Smoking: Foods preserved by smoking method are such “foods as fish, meat, and some root vegetables”. Usually it involves putting the foods in wire gauze, rack or stick over smoke coming from fire or firewood.
B. LOW TEMPERATURE TREATMENT: This include processes in which the food is subjected to a low temperature to slow the actions of micro-organisms and enzymes. it includes:
i. Freezing: This is keeping food at a low temperature (0◐c or below) in the freezer at Different kinds of foods can be preserved by freezing, e.g. fish, meat, fresh tomatoes, etc.
C. HIGH TEMPERATURE TREATMENT: This involves using heat to destroy the food enzymes and micro-organisms that may be present in foods. Use of high temperature to achieve food preservation includes:
i. Sterilization: A very high temperature that can destroy all the micro-organisms in the food is used. The foods are exposed to high temperature for longer time, and in some cases, under pressure. Example Is Milk.
ii. Pasteurization: The food is heated to a high temperature and then quickly cooled. Example include fruit juices, jams and milk.
iii. Canning: This is preservation of food by sealing it in air tight containers and applying heat. The high temperature is applied for a sufficient period of time to destroy harmful organisms. it commonly used for fruits, meats and fish.
D. USE OF PRESERVATIVES: This is the addition of substances to food to prevent it from decaying. Such substance is called food preservative.
There are two groups of preservatives, namely natural and chemical preservatives.
i. Natural Preservatives: Natural preservatives include sugar, salt, lemon juice, vinegar and oil.
*Salt:* Salt is added to food item to reduce the activity of enzymes, thus preventing the food from getting spoilt, e.g. salting of malt, and fish.
*Sugar:* Sugar is uses as a preservative in jams and jellies.
ii. Chemical Preservatives: Some edible chemical such as citric acid, sodium benzoate and potassium metabisulfile are uses to create unfavourable environment for the growth of micro-organisms and prevent chemical reactions in canned and packed foods.