Using eight methods of food preservation with different types of offood.
Drying:
This method of preserving is achieved by extracting the moisture from the food, thus preventing moulds, yeasts and bacteria from growing. This was done by drying foods, such as fruits, in the sun; today other types of equipment are used, and the food is dried by the use of air at a regulated temperature and humidity.
Foods preserved by drying are: Vegetables: peas, onions, beetroot, beans, carrots, lentils, cabbage, mixed vegetables, Potatoes fruits: applies, pears, plums (prunes), apricots, figs, grapes (sultanas, raisins, currants,). Others: Herbs, Eggs, Milk, Meat, Fish
Chilling and freezing:
Refrigeration is a method of preservation. Where the micro- organisms are not destroyed or killed, they are only prevented from multiplying. The lower the temperature the longer foods will keep. Refrigerators prevent foods from spoiling for only a short time, most frozen foods can be kept at – 170°C for a year at – 28°C for tow years. Foods must be kept in a deep freeze until required for use. Cold chilled storage of fresh foods merely stops the distortion (decoy) of the food; it does not prevent it from eventually going bad. The aim of chilling is to slow down the rate of spoilage; the lower the chill temperature within the range – 1°C = 8°C the slower the growth of microorganisms and the biochemical changes which spoil the flavour colour, texture and
nutritional value of foods. Lowering the temperature to this range also reduces food poisoning hazards although it is important to remember that
the food should not be contaminated before chilling Foods preserved by chilling are Beef, chicken, lamb etc. Foods preserved by freezing are: Fish, meat, poultry, peas, etc.
Canning and bottling:
Bottled and canned foods are sealed in air–tight bottles or tins and heated at a high enough temperature for a sufficient period of time to destroy harmful organisms. Foods preserved by Canning are: Fish, Milk, Ham, Fruit, Meat, Foods preserved by bottling are: Fruit, Herbs, Milk, Vegetables etc.
Preservation BY Salting and Smoking microorganisms cannot grow in a high concentration of salt. Foods preserved by Salting are: Fish, Meat, Poultry etc. Foods preserved by smoking are: Fish, Meat, Poultry etc.
Preservation by chemicals
Certain chemicals are permitted by law to be used to preserve certain foods such as sausages, fruit pulp, jam etc. also for domestic fruit bottling.
Preservation by acids:
Foods may be preserved in vinegar, which is acetic acid diluted with water. Foods usually pickled in vinegar are: Gherkins, capers, onions, shallots, etc
Preservation by radiation:
Foods subjected to certain rays, for example, x-rays or gamma rays are preserved.
Preservation by gas storage
Gas storage is used in conjunction with refrigerators to preserve meat, eggs, and fruit. Extra carbon dioxide added to the atmosphere surrounding the foods, increases the length of time they can be stored.
