Food Safety – Chapter 5 | Std 7 Science Solutions

Maharashtra State Board · Standard 7 · Science

Food Safety

Chapter 5 — Question & Answer Solutions

🍎 This chapter teaches us how to keep our food safe from spoilage and adulteration, and why food safety matters for our health. Read every question carefully and learn the answers in your own words.

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

Ans:

Statement	Answer
(a) Drying food grains from farms under the hot sun is called ______.	Dehydration
(b) Materials like milk are instantly cooled after heating to a certain high temperature. This method of food preservation is called ______.	Pasteurization
(c) Salt is a ______ type of food preservative.	Natural
(d) Vinegar is a ______ type of food preservative.	Chemical

Answer the following questions in your own words.

(a) How is milk pasteurized?

Ans:

Pasteurization involves heating the milk to a certain temperature and then cooling it quickly. Milk is heated to 80°C for 15 minutes and then cooled at once. This destroys the microbes present in the milk and keeps it safe for a longer duration.

(b) Why should we not consume adulterated food materials?

Ans:

The health of all people — young and old, poor or rich — is endangered by food adulteration.
Different types of adulterants affect our health in different ways.
Some adulterants cause abdominal discomfort or poisoning.
Some may affect the functioning of certain organs if consumed over a long period of time, and may even cause cancer.

Ans:

Perishable foods like milk, fruits, vegetables and cooked food are stored in proper places where they will not spoil — for example, by keeping them in a refrigerator.
Foods like papads are protected and preserved by drying them under the sun.
Foods like water and milk are boiled.
Airtight containers are used to store food.
Natural preservatives are added to foods like pickles, jams, murabba and petha.
These methods prevent the growth of microorganisms in food and keep it safe.

(d) How does food spoilage occur? Which are the various factors spoiling the food?

Ans:

Food is said to be spoiled when there is a change in its colour, texture, quantity, taste or nutrient content. Food spoilage occurs for many reasons:

When food grains from farms are damaged due to improper handling, storage or transportation.
When food is not handled properly — for example, overcooked food.
Improper storage of food — for example, storing it in a damp place.
Acidic foodstuffs like milk can spoil due to chemical reactions.
Some foodstuffs spoil due to contamination by microorganisms or insects from the air, water or soil.

(e) Which methods of food preservation would you use?

Ans:

Freezing or refrigerating: Cooked food, dairy products and poultry products can be stored in a refrigerator, as this slows the growth of microorganisms and keeps the food safe for longer.
Boiling: Boiling destroys the microbes present in food, allowing it to be kept for a longer period of time.
Drying: Drying foodstuffs removes their moisture content, preventing them from spoiling.
Airtight containers: No moisture from the environment can enter, so the foodstuffs remain safe for longer.
Natural preservatives: Pickles contain preservatives like salt and oil to keep the food unspoiled, while jams and jellies use added sugar as a natural preservative.

What shall we do?

(a) There are vendors selling uncovered sweetmeats in open places in the market.

Ans: We should avoid eating uncovered foods, as they are not safe. They may pick up microorganisms from their surroundings, which can spoil the food.

(b) A ‘pani-puriwalla’ is serving pani puri with dirty hands.

Ans: We should not consume these pani puris, as they may make us ill. There could be bacteria present on his dirty hands that may enter our system and cause illness.

Ans: Fruits and vegetables are perishable, so we should store them at a low temperature in airtight containers.

(d) We need to protect foodstuffs from pests like rats, cockroaches and wall-lizards.

Ans: We should store food in a proper place with a tight-fitting lid so that pests cannot spoil it.

Find the odd-man-out.

Ans:

Group	Odd One Out
(a) Salt, vinegar, citric acid, sodium benzoate	Salt
(b) Lakhi dal, brick dust, methanyl yellow, turmeric powder	Turmeric powder
(c) Banana, apple, guava, almond	Almond
(d) Storing, freezing, settling, drying	Settling

Complete the chart below.

Ans:

Sr. No.	Foodstuff	Adulterant
1	Turmeric powder	Metanyl yellow
2	Black pepper	Dried papaya seeds
3	Rava	Iron filings
4	Honey	Sugar, water and jaggery

Explain why this happens and suggest possible remedies.

(a) Qualitative wastage of food.

Ans:

Qualitative wastage of food may happen because of:

Wrong methods of preserving food.
Excessive use of food preservatives.
Overcooking.
Washing vegetables after cutting them.
Mishandling fruits like grapes and mangoes.

RemedyWash vegetables before cutting them, handle perishable food items very carefully, avoid overcooking, and refrigerate fruits and vegetables to maintain a suitable temperature.

(b) The cooked rice is underdone.

Ans:

Cooked rice remains underdone due to a lack of water or heat.

RemedyAdd an adequate amount of water to the vessel while preparing rice.

Ans:

If wheat is not stored properly in a dry place, moisture from the surrounding atmosphere can enter it and make it moist.

RemedyThe wheat should not be touched with wet hands. It should be dried in the sun four to five times, and then placed in clean, dry, airtight containers.

(d) The taste of yoghurt is too sour or slightly bitter.

Ans:

The taste of yoghurt may turn sour if it is not stored at a low temperature, because microbial growth in the yoghurt continues if it stays at a high temperature.

RemedyStore the yoghurt at a low temperature in the refrigerator.

(e) Cut fruits have turned black.

Ans:

Chemical reactions begin in cut fruits, which turns them black.

RemedyStore cut fruit pieces immediately in airtight containers. Seasoning the fruit pieces with a little sugar or salt also prevents blackening.

Give reasons.

1. Food remains safe at 5°C.

Ans:

At a cold temperature of 5°C, the reactions caused by microorganisms do not take place — the bacteria and fungi that spoil food remain inactive at such low temperatures.
Therefore, food items remain safe at this temperature.

2. Nowadays, food is served buffet style during large gatherings.

Ans:

The buffet style is used to prevent food waste and save food.
People are expected to serve themselves only as much food as they can consume.
The traditional method of serving food often results in wastage, so food is now served buffet style at large gatherings.

(a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms?

Ans:

No, we are not autotrophic organisms; we are heterotrophic organisms. This is because we do not have chlorophyll and cannot make our own food using sunlight. We depend on plants for grains, pulses and vegetables, and on animals for meat and eggs. Thus, we depend on both plants and animals for our food.

(b) Which organisms are greater in number — autotrophs or heterotrophs? Why?

Ans:

Autotrophs are greater in number. This is because autotrophs have chlorophyll, so they can make their own food through photosynthesis. They do not depend on other organisms for their nutrition and survival.

(c) The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why is this so?

Ans:

In desert regions, autotrophs are fewer in number, and so are the heterotrophs that depend on them. Since food is scarce, the number of heterotrophs also reduces.
In oceans and seas, there are vast numbers of zooplankton and phytoplankton. Phytoplankton are tiny, microscopic floating plants that we may not even see, and the sea’s food chain depends on these planktonic species.
Therefore, heterotrophs are fewer in desert regions but far more numerous in the sea.

(d) What damage or harm do ectoparasitic and endoparasitic animals cause?

Ans:

Parasitic organisms depend on other animals for their nutrition.
Ectoparasites live on the surface of an animal’s body and may cause intense itching and skin damage. Blood-sucking endoparasites may also lead to blood loss in animals — for example, lice, bedbugs and ticks.
Endoparasites live inside the bodies of other animals and may cause digestive problems — for example, tapeworms and roundworms.

(e) Why is plant food not produced in any other parts of the plant except the green ones?

Ans:

Chlorophyll is present only in the green parts of a plant, and photosynthesis — the process that produces food — takes place only in these parts. The non-green parts do not produce food because they lack chlorophyll.

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