5. Write about any one preservation method.
Answers
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objectives of food preservation:
- To prevent microbial contamination.
- To kill pathogens.
- To minimise food spoilage and food poisoning.
Food Preservation Methods:-
Food preservation started long back in ancient times. Cooling, freezing, fermentation, sun-drying, etc., are few age-old food preservation techniques. With the advent of technology, modern methods of food preservation were developed. Chemicals and other natural substances were used for preservation. These substances are known as preservatives.
Chemical Method:-
Salt and edible oils are two main preservatives which are used since ages to prevent microbial growth. This is why we add extra oil to pickles. Preservation by salt is known as salting. Salting 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
Sugar is another common preservative used in jams and jellies. Sugar is a good moisture absorbent. By reducing moisture content, it restrains the microbial growth.
Heat and Cold Methods
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
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.
Canning
The food contents are sealed in an airtight container at high temperatures. Meat, fish, fruits are preserved by canning.
Sterilization
This method is carried out to remove microbes from food. For eg., milk sterilization at 100°C kills the microbes.
Dehydration
It is the process of removal of water from food. It is the simplest method and prevents food spoilage by removing water.
Lyophilization
This is the process of freezing and dehydration of the frozen product under vacuum.
Radiation
This method is also known as cold sterilization. The UV rays, X rays, gamma rays kill all the unwanted microbes present in food.