CBSE Class 7 Science Advanced Biology Food and Food Preservation Long Answer Questions Set 01

Long Answer Questions

Question 1. Explain different methods of food preservation.
Answer:
1. Drying: removing water from food under sunlight or wind prevents growth of microbes, for example dry fruits and dry meat.
2. Freezing: keeping food in cold storage reduces microbial growth, for example frozen peas.
3. Smoking: exposing food to smoke from burning wood, which acts against microbes, for example smoke roasting.
4. Packing: air-tight bags and bottles prevent microbial growth, for example dry fruits.
5. Oiling/salting: salt removes moisture from the food, and oil is also used, for example pickles.
6. Sugar: used for fruits and jams.
7. Chemicals: vinegar (acetic acid) and sodium benzoate are artificial preservatives.
8. Heating and boiling: microbes cannot grow in extreme temperature.
In simple words: Food is kept safe by removing water, cooling, heating, or adding salt, sugar or chemicals.

Teacher's Note:
1. Write each method with one example.
2. Mention pasteurization as a separate method.

Question 2. Explain the process of pasteurization.
Answer:
Pasteurization is a method of heat processing of food to kill disease-causing bacteria so that the food is safe to eat.
It was first demonstrated by Louis Pasteur, a French scientist.
The food is heated to a high temperature for a few seconds and then suddenly cooled. Milk is pasteurized at 72°C for 15 seconds.
Milk, canned drinks and cheese are pasteurized.
In simple words: Heat the food briefly to kill harmful bacteria, then cool it quickly.

Teacher's Note:
1. Give the temperature and time for milk.
2. Mention the sudden cooling.

Question 3. What is food preservation? What are the factors to be kept in mind while preserving food?
Answer:
Food preservation is the science of preventing decay or spoilage of food so that it can be stored in the best condition for the future.
The food must remain safe from attack by microbes, insects, pests, etc.
The food should not lose its optimum qualities, such as colour, texture, flavour and nutritive value.
Thus food preservation keeps the quality, edibility and nutritive value intact.
In simple words: Preserved food stays safe and keeps its colour, taste and nutrition.

Teacher's Note:
1. List the qualities that must be kept.
2. Link preservation to preventing spoilage.