On what factors are most of Food preservation methods are based ?
Answers
Answer:
Food Preservation
When the availability of food is more than the present use it is preserved for future consumption. Preservation helps the food to be available in off-season and in any place. Delay in the use of fresh food alters its freshness, it palatability and its nutritive value hence such food is preserved and use for long time. Many foods cannot be preserved as such and need some type of treatment.
Food Spoilage
Spoilage of food refers to ulteration in food or undergoing some physical and chemical changes, which render the food inedible or hazardous to eat. The chief causes of food spoilage are:
The growth of microorganisms likes bacteria yeasts and moulds.
The action of enzymes that normally occur in the food.
Additional causes of spoilage include non-enzymatic reactions in food, such as oxidation, mechanical damage such as bruising and damage from rodents and insects.
Food preservation methods
All food preservation methods are based upon the general principle of preventing or retarding the causes of spoilage-microbial decomposition, enzymatic and non-enzymatic chemical reactions and damage from mechanical causes insects and rodents etc.
There are two types of preservation methods used:
Temporary preservation: In this method growth of microorganisms is only retarded or inhibited for short time.
Permanent preservation: In this method the growth of spoilage microorganisms are completely destroyed by different means.
Principles
Prevention or delay of microbial decomposition
By keeping out microorganisms (asepsis)
By removal of microorganisms e.g. by filtration.
By hindering the growth and activity of microorganisms e.g. by low temperature, drying, anaerobic conditions or chemicals.
By killing the microorganisms e.g. by heat or radiations.
2. Prevention or delay of self decomposition of food
By destruction or inactivation of food enzymes e.g. by blanching.
By delay of chemical reactions e.g. by prevention of oxidation by means of an antioxidant.
3. Prevention of damage caused by insects, animals and mechanical causes.
Preservation by Low Temperature
Freezing
Freezing may preserve foods for long periods of time provided the quality of the food is good to begin with and the temperature of storage is far enough below the actual freezing temperature of food for long preservation. In vegetables, enzyme action may still produce undesirable effects on flavour and texture during freezing. The enzymes therefore must be destroyed by heating before the vegetables are frozen.
Slow freezing process
It is also known as sharp freezing. In this method, the foods are placed in refrigerated rooms at temperatures ranging from –40C to –290C. Freezing may require from 3 to 72 hours under such conditions. Home freezing is done by sharp method.
Quick freezing process
The lower temperatures used –320 C to –400 C freeze foods so rapidly that fines crystals are formed and the time of freezing is greatly reduced over that required in sharp freezing. In quick freezing, large amount of food can be frozen in a short period of time.
Dehydro freezing
Dehydro freezing consists of drying the food to about 50% of its original weight and volume and then freezing the food to preserve it. Generally fruits, vegetables, meat, pork and poultry products are preserved by this method.
Preservation by High Temperature
The temperature and time used in heat processing a food will depend upon what effect heat has on the food and what other preservative methods are to be employed.
Pasteurisation
Pasteurisation is a heat treatment that kills part but not all the microorganisms present and usually involves the application of temperatures below 1000 C. The heating may be by means of steam, hot water, dry heat or electric currents and the products are cooled promptly after the heat treatment.
Explanation:
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Answer:
All food preservation methods are based upon the general principle of preventing or retarding the causes of spoilage-microbial decomposition, enzymatic and non-enzymatic chemical reactions and damage from mechanical causes insects and rodents etc.
Explanation:
As we see that in many food items we use preservatives such as oil mostly used in pickles so that they may not get affected by fungus (फफुंद) and also we add artificial preservatives chemicals in packed food item to increase their freshness.