Food is a source of energy but unhealthy or spoiled food is the major cause of diseases in humans. And to prevent food from becoming unhealthy, it needs to be preserved; this can be done in a variety of ways. Preservation of food is the technique to prevent food spoilage, food poisoning and microbial contamination in food.
This major technique is covering food with lids especially food that has rice and curry, to keep away flies and other insects. This is to protect it from any infection it can cause itself but this is short-term; food preservation is to preserve food for a longer time.
Food is basically preserved to prevent microbial contamination, kill pathogens, minimise food spoilage and prevent food poisoning.
Traditional food preservation can be through cooling, freezing, fermentation and sun-drying but now, there are modern methods of food preservation; chemicals and other natural substances known as preservatives.
Chemical method: Salt and edible oils are two main preservatives which are used since ages to prevent microbial growth. Preservation by salt is known as salting which helps to preserve fruits for a long term. Meats and fishes can also be preserved by salting.
Other synthetic preservatives include vinegar, sodium benzoate, sodium metabisulphite, etc.
Sugar is another common preservative used in jams and jellies. Sugar provides good moisture absorbent which restrains the microbial growth.
Boiling and refrigeration prevent around 70 percent of microbial growth. Boiling kills the microorganisms that cannot tolerate extreme temperatures. Thus, it helps in food preservation.
Refrigerators have very low temperatures. Since microbes do not get optimum temperature they need for growth, their growth is inhibited. Pasteurization developed by Louis Pasteur is used until today to preserve milk.
Smoking prevents dehydration in fish and meat and thus prevents spoilage. The wood smoke contains a large number of anti-microbial compounds that slow the rancidification of animal fats.
Sealing food like meat, fish or fruits in airtight containers at high temperatures keeps them fresh
Sterilisation: sterilization is removing microbes from food like milk. It is done at 100°C
Dehydration is another way; it is done by removing water from food.
Lyophilization: This is the process of freezing and dehydration of the frozen product under vacuum.
Radiation, also known as cold sterilization involves use of UV rays, X-rays, and gamma rays to kill all the unwanted microbes present in food.
These methods are basically based on the principle of either reducing the temperature conditions required for microbial growth or evaporating the water content.
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