FAQs on Methods of Food Preservation

Question 1

1. What are the main methods of food preservation used to keep food fresh longer?

Accepted Answer

Ans. The primary food preservation methods are refrigeration, freezing, drying, salting, pickling, canning, and pasteurisation. Refrigeration slows bacterial growth, while freezing halts it completely. Drying removes moisture that microorganisms need. Salting and pickling create hostile environments for microbes. Canning seals food in sterile containers, and pasteurisation uses heat to kill harmful bacteria, extending shelf life significantly.

Question 2

2. Why does salt prevent food from spoiling and how does salting work as a preservation technique?

Accepted Answer

Ans. Salting works by drawing out moisture from food through osmosis, depriving bacteria and fungi of water needed for survival and growth. High salt concentration creates an inhospitable environment where microorganisms cannot thrive. This ancient preservation method is particularly effective for meats, fish, and vegetables, allowing food to be stored for extended periods without refrigeration or modern technology.

Question 3

3. What's the difference between freezing and refrigeration for food preservation?

Accepted Answer

Ans. Refrigeration cools food to 4°C, slowing microbial growth and enzyme activity but not stopping them completely. Freezing reduces temperature to -18°C or below, completely halting bacterial reproduction and chemical reactions. Frozen food lasts months longer than refrigerated items. However, refrigeration is more convenient for short-term storage, while freezing suits long-term preservation of meat, vegetables, and prepared meals.

Question 4

4. How does drying food like fruits and vegetables actually preserve them for longer?

Accepted Answer

Ans. Drying removes moisture content that microorganisms require to multiply and survive. Without water, bacteria, fungi, and moulds cannot grow or cause spoilage. Traditional sun-drying and modern dehydration methods concentrate nutrients and flavours while extending shelf life significantly. Dried foods like fruits, vegetables, and herbs remain stable for months or years when stored in cool, dry conditions away from humidity.

Question 5

5. What happens to food during canning and why does it prevent spoilage in CBSE Class 8 Science?

Accepted Answer

Ans. Canning involves heating food to high temperatures, killing microorganisms and enzymes responsible for spoilage. The food is then sealed in sterile containers, preventing recontamination. Heat processing destroys pathogenic bacteria whilst the airtight seal maintains an oxygen-free environment where remaining microbes cannot survive. This preservation method is highly reliable for fruits, vegetables, and pickles, offering shelf life of 1-2 years or more.

Methods of Food Preservation Video Lecture - Science Class 8

Science Class 8

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New NCERTs

ICSE

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