1. Food can also be preserved with salt. This process is called salting. 2. Salting can be done in two ways as shown below. a) Adding a lot of salt to the food. b) Soaking the food in a salt solution. 3. Bacteria and fungi cannot grow in salty conditions. Hence, salted foods last longer. 4. Examples of food that can be preserved by salting are fish, meat, eggs, vegetables and fruits. 5. Salting will change the taste, colour and destroy food nutrition.
1. Pasteurising is a process in which milk is heated at 63°C for 30 minutes or heated at 72 °C fo 15 seconds and followed by rapid cooling to below 10 °C.
2. The pasteurised milk can then be refrigerated to last a few days.
3. Friut juice can also be preserved in this way.
4. This method of preservation retains the natural flavour of milk. Nutriens like vitamins are not destroyed.
1. Some foods can be canned and bottled. The canning and bottling of food allows the food to be kept for a very long time. 2. These methods of preservation involve: a) heating of the food to a very high temperature - can kill bacteria and fungi b) keeping foods in airtight cans or bottles - to prevent the entry of air that may contain bacteria and fungi 3. Therefore, canned or bottled foods can be kept for a long time in months or years. 4. Examples of food that can be perserved by canning or bottling are shown below.
1. Food can be preserved by soaking it in an acidic solution (vinegar) or saturated sugar solution. This process is known as pickling. 2. Bacteria and fungi cannot grow in acidic conditions or in saturated sugar solutions. 3. Therefore, pickled foods last longer and cannot be spoilt easily. 4. However, its taste will be different and it becomes less nutritions. 5. Examples of food that can be preserved by pickling are fruits such as mango, papaya and guava. 6. Mango pickling can be done as follows. a) Cut some green mangoes. b) Wash and drain the mango slices. c) Mix the mango slices with salt and leave them overnight. d) Wash and drain the mango slices again. e) Soak the mango slices in sugar solution for several days. f) Add a little bit of vinegar an seal the bottle tightly.
1. Cooling ia a process in which foods are kept at low temperature (0°C - 5 °C). 2. Examples of food preserved by cooling are vegetables, friuts, eggs, margarine, cheese and milk. 3. Freezing is a process in which food is cooled at a very low temperature (below 0°C) until it freezes. 4. Examples of food preserved by freezing are fish, meat, chicken, prwans, cuttlefish, meat balls and ice-cream. 5. Cooling and freezing can be done by keeping the foods in a refrigerator at home. 6. In the case of cooling, the idea is to slow bacterial action so that it takes food much longer (perhaps a week or two) to spoil. 7. In the case of freezing, the idea is to stop bacterial action altogether. Frozen bacteria are completely inactive. 8. Bacteria and fungi becomes active again when the food is taken out from the refrigerator. 9. Therefore, after taking out food from the refrigerator, it must be cooked or eated quickly before spoils. 10. The advantages of preserving food by cooling and freezing are : a) the freshness a food is preserved. b) nutrition content in the food is not destroyed
