Science textbook solutions for Class 7 science Chapter 5 Food Safety


Important points to remember :
  1. All constituents of food-carbohydrates, fats, proteins, vitamins, minerals, fibre and water are necessary for the proper growth of the body. 
  2. The foodstuffs we consume, whether of animal or plant source, must be of the best quality.  Otherwise, we may fall prey to disease or illness. 
  3. Food is said to be spoiled if there is a change in its colour, odour, texture, quality, taste and there is a loss of its nutrient  content. 
  4. various methods  of safe storage of food like freezing, drying, boiling, air-tight packing, etc. 
  5. These different methods prevent the growth of micro-organisms in food and thereby  save the food from spoiling. 
  6. The health of all people, young and old, poor or rich, is endangered by food adulteration. 


Question 1: Complete the following statements by using the correct option from those given below.
(Irradiation, dehydration, pasteurization, natural, chemical)

a) Drying the food grains from farms under the hot sun is called dehydration.

b) Materials like milk are instantly cooled after heating up to a certain high temperature. This method of food preservation is called pasteurization.

c) Salt is a natural type of food preservative.

d) Vinegar is a chemical type of food preservative.

Question 2: Answer the following questions in your own words.
a) How is milk pasteurized?
Answer : Milk is pasteurized by heating at  80°C for 15 minutes and  cooling it quickly. This destroys the microbes present in the milk  and it keeps for a longer duration.

b) Why should we not consume adulterated food materials?
Answer : We should not consume adulterated food materials because it affects our health. It is unsafe & impure. Adulterated food can cause stomach disorder, food poisoning,cancer, heart problems, giddiness, Diarrhoea, infertility, allergies, anaemia,brain damage, paralysis, hyperactivity etc.

c) What precautions do your parents take to keep foodstuffs safe?
Answer : Preparing and Cooking Raw Meat, Poultry, Fish, and Egg Products. Wash your hands with warm water and soap before preparing foods and after handling raw meat, poultry, fish, or egg products. Keep raw meats and their juices away from other foods in the refrigerator and on countertops. Never wash raw chicken.

d) How does food spoilage occur? Which are the various factors spoiling the food?
Answer : Various factors cause food spoilage, making items unsuitable for consumption. Light, oxygen, heat, humidity, temperature, and spoilage bacteria can all affect both safety and quality of perishable foods. Microbial spoilage results from bacteria, molds, and yeast.

e) Which methods of food preservation would you use?
Answer :

  1. Freezing Biological and  chemical reactions in  food materials  are  slowed down at low temperature.  As a result,  food remains in good condition for a longer duration. That is why, refrigerators are used in the kitchen.
  2. Pasteurisation This method involves heating the milk or other similar foodstuffs up to a certain  temperature, e.g., milk at  80o  C for  15  minutes and  cooling it quickly. This destroys the microbes present in the milk  and it keeps for a longer duration.
  3. Salting : Some naturally available materials like salt, sugar,  oil are used as preservatives in pickles, jams,  murabba,  petha, etc. Chemical.
  4. Acetic acid (vinegar), citric acid, sodium benzoate and some nitrate  and nitrite salts are some examples of chemical preservatives.  They are used in sauces, jellies, jams,  and in  packaged  readyto-cook vegetables and  readyto-eat foods, etc. These preservatives keep the  food safe for a very long duration.



Question 3: What shall we do?
a) There are vendors selling uncovered sweetmeats in open places in the market.
Answer : The vendors selling the sweetmeats in open surface should totally avoid this. They should cover the selling articles to maintain its safety. The open food that too dead parts are often subjected to the accumulation of various dirt and germs that ruins the nutrient content of the food particles.

b) A 'pani-puriwalla' is serving the pani puri with dirty hands.
Answer : Answer: If panipuri wala is serving panipuri with dirty hands, we must avoid panipuri from such stall. Explanation: Ideally, we can advise and explain to him how his dirty hands could cause infection to hundreds of people including him.

c) We have purchased a large quantity of fruits and vegetables.
Answer : If we have purchased large amounts of fruits and vegetables, then we need to store them properly. ... Vegetables can be cut and stored in deep freezers and then used as and when required. Some vegetables can also be used in making pickles.

d) We need to protect foodstuffs from pests like rats, cockroaches, wall-lizards, etc.
Answer : Insects and pests like rats, cockroaches etc. are the conductor of different diseases , these insects spread diseases by contaminating our food items. To prevent this contamination we should always cover our food materials ,and arrange pest controls if needed.


Question 4: Find the odd-man-out.
a) salt, vinegar, citric acid, sodium benzoate
Answer : salt is the odd one out beacuse it is natural preservative while rest of them are chemical preservatives.

b) lakhi dal, brick dust, metanyl yellow, turmeric powder - 
Answer : turmeric powder is the odd one out because it is a type of spice while the rest of the three are adulterants.

c) banana, apple, guava, almond- 
Answer : almond is the odd one our because it is a dry fruit whereas the rest of the three are fresh fruits.

d) storing, freezing, settling, drying- 
Answer : settling is the odd one out because rest of the three are preservation methods.

Question 5 : Complete the chart below.
Answer :
1.Turmeric powder - Metanyl yellow
2. Black pepper - Papaya seeds
3.Rava - Iron filings
4. Honey - Sugar


Question 6: Explain why this happens and suggest possible remedies.
a) Qualitative wastage of food.
Answer : The qualitative food wastage is the one that is done during the supply chain of the products. It is done on the initial level only with no condition to take down in the household. This type of waste is not even consumed by a single person but it spoilt and thrown away.

b) The cooked rice is underdone.
Answer : The cooked rice is underdone. It is due to the fact that the rice is kept stored for a long time and it loses water. Explanation: This cooked rice is not harmful to eat but to make it eatable one should add a cup of water to let it regain its original form.

c) The wheat that was bought is a bit moist.
Answer : Wheat that is brought is moist because wheat is harvested when there is some water content in the wheat. EXPLANATION: When harvested, wheat contains some water content which is not dried completely and is circulated in the market for selling.

d) The taste of yoghurt is too sour/slightly bitter.
Answer : All you need is pasteurized milk and bacteria. With such a high volume of active bacteria chugging away, the end result becomes supremely tangy. For some, that sour taste is anything but tasty, so many varieties of yogurt come adorned with additives ranging from honey to fruit preserves to balance out the flavor

e) Cut fruits have turned black.
Answer : When fresh fruits and vegetables are peeled or cut open, the enzyme called polyphenol oxidase (also called tyrosinase) contained in the cells is exposed to and reacts with the oxygen in the air. The bruising seen on some fruit, such as apples and pears, is caused by the same type of reaction.


Question 7: Give reasons.
1. Food remains safe at 5° Celsius.
Answer : Food remains safe at 5oC because this temperature prevents the growth of microorganisms. Microorganisms usually require hot and humid places to grow whereas at this temperature they cannot grow and survive. Their metabolic activities are inhibited at this temperature.

2. Nowadays, food is served buffet style during large gatherings.
Answer :  Nowadays food is served in buffet style during large gathering because ​buffet is a self service dinning system in restaurants where it allows you to serve variety of dishes at a time.


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