Food preservation is the process of treating and handling food to stop or slow down spoilage (loss of quality, edibility or nutritional value) and thus allow for longer storage. Preservation usually involves preventing the growth of bacteria, yeasts, fungi, and other micro-organisms (although some methods work by introducing benign bacteria, or fungi to the food), as well as retarding the oxidation of fats which cause rancidity. Food preservation can also include processes which inhibit visual deterioration (when something becomes less close to the original) that can occur during food preparation; such as the enzymatic browning reaction in apples after they are cut.
Many processes designed to preserve food will involve a number of food preservation methods. Preserving fruit, by turning it into jam, for example, involves boiling (to reduce the fruit’s moisture content and to kill bacteria, yeasts, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). There are many traditional methods of preserving food that limit the energy inputs and reduce carbon footprint. Maintaining or creating nutritional value, texture and flavor is an important aspect of food preservation, although, historically, some methods drastically altered the character of the food being preserved. In many cases these changes have now come to be seen as desirable qualities – cheese, yoghurt and pickled onions being common examples.
1. Our food comes from animals and plants.
2. Fresh products such as fruits, milk and vegetables do not last long if kept at room temperature. 3. Food turns bad because of bacteria and fungi.
4. However, not all bacteria and fungi are harmful.
5. When food spoilt, it usually changes in appearance.
6. The action of bacteria and fungi causes spoilt food to; * Emit an unpleasant smell
* Have an unpleasant taste
* Change color
* Change in texture
* Become mouldy
* Become slimy
Micro-organisms Can Spoil Food
1. The growth of micro-organisms such as fungi and bacteria can spoil food. 2. Fungi and bacteria can grow wisely on damp foods that are exposed to the air. 3. Fungi and bacteria change the food material into simple substances. 4. These simple substances may be poisonous.
5. Spoilt food is unsafe to eat because it contains poisonous substance. 6. We can get food poisoning if we eat spoilt food.
7. Eating spoilt food can also cause bacterial and fungal infections. 8. The conditions suitable for the growth of micro-organisms are; * Water
* A suitable temperature and suitable acidity
Methods of Food Preservation
Drying consists in removing the water from a product. This can be done through heating, creating a vacuum or using chemicals that’ll absorb the water (e.g. concentrated sulfuric acid), or through slow progressive drying. This is a way of preserving food in so far as microbes can’t develop without water. Dehydration is a particularly well adapted way of preserving herbs, fruits or even vegetables. Dehydration and lactic acid fermentation are the healthiest methods of food preservation as the vitamins are kept intact and rebuild themselves when the food is rehydrated. Besides, this sort of food is easy to carry (e.g. for holidaymakers) and medicinal herbs, they keep all their properties There are solar dryers : especially useful for cold or temperate climates (Quebec…), though they can be used in Summer only, when nights get colder, drying is less easy as moist can penetrate the plant if there is no additional heating.
1. Drying involves the removal of water contained in the food. There are three ways...
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