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Food and Preservation

NCERT Class 5 · EVS Based on NCERT Class 5 EVS textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter explores why food spoils, how to preserve it, and the role of microbes in both spoilage and digestion. It follows Detective Disha as she investigates the mystery of a spoiled uttapam and learns about traditional Indian preservation methods like drying, pickling, and refrigeration. The big idea is that food spoils because of tiny living things called microbes, and we can stop them by removing moisture, air, or keeping food at the right temperature. Students must understand that not all microbes are harmful—some help us make curd, idlis, and even digest our food.
Key Concepts (17)
Microbes
Tiny living things that are found everywhere—in soil, water, air, plants, animals, and inside us. They are so small that they can only be seen with a microscope.
e.g. The coloured patches on the forgotten uttapam were mould, which is a colony of thousands of microbes.
Mould
A visible growth of microbes that appears as coloured patches on spoiled food.
e.g. The greenish or blackish patches on old bread or uttapam are mould.
Food Spoilage
The process by which food changes in taste, smell, and appearance due to the growth of microbes.
e.g. The uttapam left in the tiffin box for three days developed a foul smell and coloured patches.
Food Preservation
Methods used to keep food from spoiling by stopping the growth of microbes.
e.g. Drying chillies in the sun, adding oil to pickles, and keeping milk in the fridge are all methods of food preservation.
Drying or Dehydration
A method of food preservation that removes moisture from food so that microbes cannot grow.
e.g. Chillies are dried in the sun to make chilli powder that lasts for the entire year.
Pickling and Oiling
A method of food preservation where oil is added to food to keep air out and stop the growth of microbes.
e.g. Mustard oil is poured into a jar of pickled green mangoes to keep them safe.
Refrigeration and Freezing
A method of food preservation that uses cold temperature to slow down the growth of microbes.
e.g. Milk, vegetables, butter, and cake are stored in the fridge to keep them fresh longer.
Saliva
A liquid released in the mouth when we chew food. It helps in digestion.
e.g. Chewing food properly releases more saliva, which helps break down the food.
Incisors
The front teeth used to cut food.
e.g. We use incisors to bite into an apple.
Canines
The pointed teeth used to tear food.
e.g. We use canines to tear a piece of chapati or meat.
Premolars
Teeth used to crush food.
e.g. We use premolars to crush a piece of carrot.
Molars
The back teeth used to grind food.
e.g. We use molars to grind food into a mush before swallowing.
Cavity
A hole in the tooth caused by decay, which can lead to toothache.
e.g. The dentist found a cavity in Disha's tooth and treated it.
Oral Hygiene
The practice of keeping the mouth, teeth, and gums clean to prevent problems like cavities.
e.g. Rinsing the mouth after eating and brushing teeth regularly are part of oral hygiene.
Choking
A dangerous situation when food gets stuck in the throat and blocks breathing.
e.g. Gulping down food without chewing properly can cause choking.
Fermented Rice
Rice that has been left to ferment, eaten in many parts of India as pakhala or kanji. It cools the body and contains good bacteria.
e.g. In Odisha, people eat pakhala, which is fermented rice, especially in summer.
Good Microbes
Microbes that are helpful to us, such as those that make curd, help idli batter rise, and aid digestion.
e.g. The microbes in curd join the good microbes in our stomach to help digest food.
How It Works
How Food Spoils
  1. Microbes land on food from the air, water, or surfaces.
  2. If the food has moisture, air, and is at the right temperature, microbes begin to grow.
  3. As microbes multiply, they change the taste, smell, and appearance of the food, causing it to spoil.
💡 Microbes need three things to grow: moisture, air, and the right temperature. Remove any one, and you stop spoilage.
Drying or Dehydration
  1. Food items like chillies, papads, or mango slices are spread on a mat or tray.
  2. They are placed in direct sunlight for several days.
  3. The sun's heat removes the moisture from the food.
  4. Without moisture, microbes cannot grow, so the food remains unspoilt for a long time.
💡 Drying removes moisture—this is the key. Students often forget that moisture is the target, not the heat itself.
Pickling and Oiling
  1. Food items like mangoes or lemons are cut and mixed with salt and spices.
  2. The mixture is placed in a clean, dry jar.
  3. Mustard oil or another oil is poured over the pickle until it completely covers the food.
  4. The oil forms a layer that blocks air from reaching the food.
  5. Without air, microbes cannot grow, so the pickle stays safe for months.
💡 Oil keeps air out. Students often think the salt or spices do the preserving, but the oil's role in blocking air is equally important.
Refrigeration and Freezing
  1. Food is placed inside a refrigerator or freezer.
  2. The appliance lowers the temperature to a level that is too cold for microbes to grow actively.
  3. Microbes become inactive or slow down significantly.
  4. The food stays fresh for a longer period compared to being kept at room temperature.
💡 Refrigeration slows down microbes—it does not kill them. Food can still spoil if left in the fridge for too long.
How Idlis Are Made (Role of Microbes)
  1. Rice and urad dal are soaked and ground into a batter.
  2. The batter is left to ferment overnight.
  3. Microbes present in the air enter the batter and begin to grow.
  4. These microbes produce gas bubbles, which make the batter rise and become fluffy.
  5. When the batter is steamed, the gas bubbles expand, giving idlis their soft, spongy texture.
💡 The microbes that make idli batter rise are good microbes—they come from the air. Students sometimes think the fluffiness comes from a chemical, not from microbes.
Chewing and Digestion in the Mouth
  1. Food enters the mouth and is cut by incisors, torn by canines, crushed by premolars, and ground by molars.
  2. Chewing breaks the food into smaller pieces and then into a mush.
  3. The action of chewing stimulates the release of saliva.
  4. Saliva mixes with the food and begins the process of digestion.
💡 Chewing properly is essential—it releases saliva and breaks food down. Gulping food without chewing can cause choking and poor digestion.
Exam Traps — Don't Make These Mistakes
⚠ Confusing 'microbes' with 'insects' or 'lice'
✗ Microbes are tiny insects or lice that spoil food.
→ Microbes are not insects. They are living things so small they can only be seen with a microscope. Insects like ants or flies are visible to the naked eye.
✓ Microbes are tiny living things that are found everywhere—in soil, water, air, and inside our bodies. They are so small that a microscope is needed to see them.
⚠ Thinking all microbes are harmful
✗ Microbes are bad because they spoil food and cause diseases.
→ Not all microbes are harmful. Some microbes are helpful—they help make curd, make idli batter rise, and help digest food in our stomach.
✓ Some microbes spoil food and can cause illness, but other microbes are good. Good microbes help us make curd, idlis, and even digest our food.
⚠ Confusing why butter needs refrigeration but ghee does not
✗ Butter needs refrigeration because it is made from milk, and ghee does not because it is made from butter.
→ The real reason is that ghee has had all its water removed during preparation, so microbes cannot grow in it. Butter still contains water, so microbes can grow if it is not kept cold.
✓ Butter needs refrigeration because it contains water, which allows microbes to grow. Ghee is made by heating butter until all water evaporates, so it has no moisture and can be stored without refrigeration.
⚠ Thinking oil preserves food by adding flavour, not by blocking air
✗ Oil is added to pickles to make them taste better.
→ While oil does add flavour, its main purpose in preservation is to create a barrier that keeps air out. Microbes need air to grow, so blocking air stops spoilage.
✓ Oil is added to pickles to keep air out. Without air, microbes cannot grow, so the pickle remains safe to eat for a long time.
⚠ Confusing 'drying' with 'cooking'
✗ Drying food means cooking it in the sun.
→ Drying is not cooking. Cooking uses heat to change the food's texture and taste, often with water or oil. Drying simply removes moisture from the food without cooking it.
✓ Drying or dehydration is a method of food preservation where moisture is removed from food, usually by sunlight, so that microbes cannot grow.
⚠ Thinking refrigeration kills all microbes
✗ Refrigeration kills all the microbes in food, so the food never spoils.
→ Refrigeration only slows down the growth of microbes—it does not kill them. Some microbes can still grow slowly in the fridge, and food will eventually spoil if kept too long.
✓ Refrigeration slows down the growth of microbes by making the temperature too cold for them to grow actively. It does not kill them, so food can still spoil over time.
Compare & Contrast
Effect on food and health
Good Microbes
Bad Microbes
Good microbes help us make food items like curd and idlis, and help digest food in our stomach. Bad microbes spoil food by causing foul smell, coloured patches, and can cause indigestion or illness if eaten.
Need for refrigeration
Butter
Ghee
Butter contains water, so it needs refrigeration to prevent microbe growth. Ghee is made by heating butter until all water evaporates, so it has no moisture and can be stored at room temperature without spoiling.
Method of stopping microbe growth
Drying
Pickling with Oil
Drying removes moisture from food so microbes cannot grow. Pickling with oil creates a layer that blocks air from reaching the food, so microbes cannot grow.
Exam Focus
Marks pattern: 2 MCQs (1 mark each), 1 Short Answer (3 marks) on preservation methods, 1 Long Answer (5 marks) on causes of spoilage and prevention, 1 Very Short Answer (1 mark) on good microbes
Most asked: Causes of food spoilage (microbes, moisture, air, temperature) · Methods of food preservation (drying, pickling, refrigeration, canning) · Role of good microbes in making curd and idlis · Importance of chewing food properly and oral hygiene
Don't skip: Explain any three methods of food preservation with examples.; Why do some foods spoil faster than others? Explain with examples from the chapter.; Describe the role of microbes in making idlis and curd.
One-Line Revision (read aloud before the exam)
  1. Microbes are tiny living things that can only be seen with a microscope and are found everywhere around us.
  2. Food spoils because microbes grow on it when moisture, air, and the right temperature are present.
  3. Drying removes moisture from food and stops microbes from growing.
  4. Oil is added to pickles to keep air out and prevent microbe growth.
  5. Refrigeration slows down the growth of microbes by keeping food cold.
  6. Ghee does not need refrigeration because all water is removed during its preparation.
  7. Good microbes help make curd and help idli batter rise by producing gas.
  8. Chewing food properly releases saliva, which helps in digestion.
  9. Different teeth have different jobs: incisors cut, canines tear, premolars crush, and molars grind.
  10. Oral hygiene means rinsing your mouth after eating and brushing your teeth regularly.
  11. Eating food too fast or gulping can cause choking.
  12. Seasonal fruits taste best when eaten in their season, and waiting for them increases the joy.
  13. Fermented rice like pakhala or kanji is eaten in many parts of India and contains good bacteria.
  14. Not all microbes are harmful—some help us digest food and make tasty food items.

MCQs — 10 Questions with Answers

Q1. What are microbes?

  • A. Tiny living things so small you need a microscope to see them ✓
  • B. Large insects found in kitchens
  • C. A type of dirt that makes food dirty
  • D. Coloured patches visible on all foods

Answer: A — Microbes are microscopic living organisms found everywhere and need a microscope to be seen, as stated in the chapter when Disha's brother explains them to her.

Q2. What is mould?

  • A. A type of dust that makes food unclean
  • B. A colony of thousands of microbes appearing as coloured patches on food ✓
  • C. A spice used in Indian cooking
  • D. A type of bacteria found only in kitchens

Answer: B — The chapter explains that mould is a visible colony made of thousands of microbes that appear as coloured patches on food like Disha's uttapam.

Q3. Microbes need three things to grow. Which one is NOT mentioned in the chapter?

  • A. Moisture or water
  • B. Air
  • C. Right temperature
  • D. Sunlight ✓

Answer: D — The chapter clearly states that microbes need only three things to grow: moisture, air, and the right temperature — not sunlight.

Q4. Why did Disha's Paati add oil to the pickled green mangoes?

  • A. To make the pickles taste better
  • B. To add nutrition to the pickles
  • C. To stop air from getting in and prevent microbe growth ✓
  • D. To keep the pickles cool in the kitchen

Answer: C — In the chapter, Disha's grandmother explains that oil is added because it stops air from getting in, which prevents microbes from growing and keeps pickles safe.

Q5. Which method of food preservation works by removing moisture?

  • A. Refrigeration
  • B. Pickling with oil
  • C. Drying in the sun ✓
  • D. Adding salt only

Answer: C — The chapter shows that drying chillies in the sun removes moisture, and without water, microbes cannot grow, making this an effective preservation method.

Q6. What does a refrigerator do to microbes?

  • A. It kills all the microbes instantly
  • B. It stops microbes from existing
  • C. It slows down the growth of microbes ✓
  • D. It removes air so microbes cannot survive

Answer: C — The chapter states that the cold temperature in a refrigerator slows down microbe growth, which is why milk, vegetables, and cake stay fresh longer inside.

Q7. Fill in the blank: Microbes are found in soil, water, air, and _______.

  • A. only in kitchens
  • B. only on spoiled food
  • C. inside plants, animals, and us ✓
  • D. only on dirty surfaces

Answer: C — Finding #1 in the chapter clearly states that microbes are found in soil, water, air, and also in plants, animals, and inside us.

Q8. Which of these is an example of a good microbe?

  • A. Microbe that causes mould on bread
  • B. Microbe that spoils pickles
  • C. Microbe that helps make curd from milk ✓
  • D. Microbe that causes upset stomach

Answer: C — The chapter explains that some microbes help us — for example, the microbe that makes curd and helps our body digest food are good microbes.

Q9. Why did the bread left on Disha's balcony get coloured patches after two days, but the pickles stayed fresh for two months?

  • A. The bread was exposed to sun while pickles were not
  • B. The bread had moisture and air, while oil on pickles blocked air ✓
  • C. The pickles had more salt than the bread
  • D. The bread was older than the pickles

Answer: B — The chapter shows that bread exposed to air and moisture allows microbes to grow (causing mould), while oil on pickles blocks air, preventing microbe growth and keeping them fresh.

Q10. According to the chapter, if we remove even one of the three things microbes need, what happens?

  • A. Microbes grow faster
  • B. Microbes stop growing ✓
  • C. Food tastes better
  • D. Temperature increases in the food

Answer: B — Finding #2 states that if we remove any one of the three needs (moisture, air, or temperature), we can stop microbes from growing.

Flashcards

What are microbes?

Tiny living things found everywhere — in soil, water, air, and even inside us — so small you need a microscope to see them.

What is mould?

A visible colony made of thousands of microbes growing together on food, appearing as coloured patches and causing spoilage.

Name three things microbes need to grow.

Moisture (water), air, and the right temperature are the three things microbes must have to grow and multiply.

How does drying preserve food?

Drying removes moisture from food; without water, microbes cannot grow, so food stays fresh for a long time.

Why does oil on pickles prevent spoilage?

Oil blocks air from getting inside the jar; without air, microbes cannot grow and the pickles stay safe.

What happens to microbes in a refrigerator?

Cold temperature from the fridge slows down the growth of microbes, keeping milk, vegetables, and other foods fresh longer.

Give one example of a good microbe.

The microbe that helps make curd from milk is a good microbe; it also helps our body digest food.

What happened to Disha's uttapam in the forgotten lunch box?

Microbes grew on it and created coloured mould patches, making it smell bad and unsuitable to eat after three days.

Name one traditional Indian food preservation method.

Pickling with salt, sugar, spices, or oil is a traditional Indian method that has kept foods fresh for months or years.

Why is it important to understand food spoilage?

Understanding why food spoils helps us store food safely, avoid eating spoiled food that causes upset stomachs, and stay healthy.

Important Board Questions

What are microbes? [1 mark]

Define microbes as tiny living things invisible without a microscope; mention they are found everywhere — soil, water, air, and inside us.

Name any two methods of food preservation and explain how each one stops microbes from growing. [2 marks]

Choose two from: drying (removes moisture), oiling (blocks air), refrigeration (slows growth with cold), or pickling (uses salt/spices). Explain the mechanism for each.

Disha found coloured patches on her uttapam after three days. Explain why this happened and what she could have done to prevent it. Give one example from your home. [3 marks]

Explain that microbes caused mould growth because of moisture, air, and warm temperature. Mention one preservation method (drying, oiling, or refrigeration) and give a home example like dried chillies, pickles with oil, or leftover curry in fridge.

Detective Disha discovered that microbes need three things to grow and multiply. Identify these three things, explain what happens when one is removed, and describe two traditional Indian food preservation methods that use this knowledge. [5 marks]

Three needs: moisture, air, temperature. Explain that removing any one stops growth. Describe drying (removes water), oiling (blocks air), pickling (combines salt/spices), and refrigeration (reduces temperature). Draw a simple diagram showing oil layer on pickle jar blocking air.

True or False: (a) All microbes are harmful and cause food spoilage. (b) Mould is just dirt on food. Give one reason for each answer. [2 marks]

Both are FALSE. (a) Good microbes make curd and help digestion. (b) Mould is a colony of living microbes, not dirt.

Assertion-Reason Questions for Food and Preservation

Q1. Assertion (A):

Microbes are tiny living things that cannot be seen without a microscope.

Reason (R):

Microbes are found only in spoiled food and not anywhere else in nature.

Answer: C — A is true but R is false — The assertion is true — microbes are indeed tiny and need a microscope to see. However, the reason is false because microbes are found everywhere (soil, water, air, plants, animals, inside us), not just in spoiled food. Some microbes are even helpful, like those making curd.

Q2. Assertion (A):

Food spoils because microbes grow on it and change its taste and smell.

Reason (R):

Microbes need moisture, air, and the right temperature to grow.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why food spoils. Microbes need these three conditions to grow, and when they do, they cause the food to spoil, changing its color, smell, and taste.

Q3. Assertion (A):

Drying food in the sun is a good way to preserve it for long periods.

Reason (R):

Drying removes moisture, which is one of the things microbes need to grow.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true. Drying food (like chillies) in the sun removes moisture, and without moisture, microbes cannot grow. This is why Disha's parents dried chillies and they lasted the entire year.

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Case-Based Questions (CBQ) for Food and Preservation

Case Study:

Ravi's mother prepared a homemade lunch for him to take to school. She packed rice with vegetables in a steel lunch box. Ravi kept the lunch box on his school desk in the classroom, which was warm and had no air conditioning. When he opened the box during lunch time after 5 hours, he noticed a bad smell coming from the food. By evening, his mother saw that the food had developed some coloured patches on it.

Q1. Why did the food in Ravi's lunch box spoil so quickly?

  • A. The steel lunch box was not clean
  • B. The food had moisture and was kept in a warm classroom with air, providing perfect conditions for microbes to grow ✓
  • C. The vegetables were old
  • D. The lunch box was opened too many times

Answer: B

Q2. What are the coloured patches that appeared on the food most likely to be?

  • A. Dust from the classroom
  • B. Dirt that entered the lunch box
  • C. Mould made up of colonies of microbes ✓
  • D. Spices that changed color in heat

Answer: C

Q3. How could Ravi's mother have preserved the food better for school?

  • A. By packing the food in a plastic box instead
  • B. By putting the lunch box in the refrigerator before Ravi left for school, so it stays cool during the day ✓
  • C. By adding more salt to the food
  • D. By packing the food in larger containers

Answer: B

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