Grade 5 Chapter 13: Methods of Preserving Food

Topics covered: Why food spoils, Causes of food spoilage, Methods of food preservation (drying, cooling, boiling, pickling, etc.), Importance of food preservation.

Why Does Food Spoil?

Can you tell?

• What happens to bread if it is left out for a few days?
• How do you know if milk has gone bad?
• Why do we keep cooked food in the refrigerator?

Food does not remain fresh forever. After some time, it starts to spoil. When food spoils, its taste, smell, and appearance change. Spoiled food can make us sick if we eat it. Food spoilage is caused by tiny living things called micro-organisms (like bacteria and fungi) that grow on food, especially when there is moisture and warmth.

Sometimes, food also spoils if it is not stored properly or if it comes into contact with dirt or insects.

Think about it:

1. What are the signs that food has spoiled?
2. Why does food spoil faster in summer than in winter?

Causes of Food Spoilage

Let’s try this (Activity):

1. Take a piece of bread and sprinkle some water on it.
2. Keep it in a closed box in a warm place for a few days.
3. Observe what happens to the bread. (Do not eat it!)

You will see a fuzzy growth on the bread. This is a type of fungus (a micro-organism) that grows in the presence of moisture and warmth. Micro-organisms need moisture, warmth, and food to grow. When they grow on our food, they break it down and cause it to spoil.

Other factors that cause food spoilage include:

• Moisture: Water content in food helps micro-organisms grow.
• Temperature: Warm temperatures speed up spoilage. Cold temperatures slow it down.
• Air: Exposure to air can also lead to spoilage for some foods.
• Enzymes: Natural chemicals in food that cause it to ripen and eventually spoil.

Use your brain power!

1. Why does dry food like grains not spoil as quickly as fresh vegetables?

   Answer: Dry food has very little moisture, which makes it difficult for micro-organisms to grow.

2. How does covering food help prevent it from spoiling quickly?

   Answer: It protects the food from dust, insects, and reduces exposure to air, which can slow down spoilage.

Always remember: Micro-organisms need moisture and warmth to grow and spoil food.

Methods of Food Preservation

Since food spoils easily, we need ways to keep it fresh for longer. These methods are called food preservation methods. They work by either removing moisture, making the environment unsuitable for micro-organisms, or killing them.

1. Drying (Dehydration)

Let’s try this (Activity):

1. Cut some vegetables like lady's fingers or potatoes into thin slices.
2. Spread them out in the sun to dry completely.
3. Observe after a few days.

When food is dried, the moisture content is removed. Without moisture, micro-organisms cannot grow. This method is used for grains, pulses, spices, and even some vegetables and fruits like grapes (to make raisins).

2. Cooling (Refrigeration)

Keeping food in a refrigerator or a cold place slows down the growth of micro-organisms. This is why we store milk, cooked food, fruits, and vegetables in the fridge to keep them fresh for a few days.

3. Boiling

Boiling food, especially liquids like milk and water, kills the micro-organisms present in them. This makes them safe for consumption and helps them last longer. We boil milk before drinking it to kill harmful bacteria.

4. Pickling

Adding salt, sugar, oil, and spices to food creates an environment where micro-organisms cannot easily grow. This method is commonly used for making pickles from mangoes, lemons, or other vegetables. The high salt or sugar content acts as a preservative.

5. Canning and Bottling

In this method, food is cooked, sealed in airtight cans or bottles, and then heated to kill any remaining micro-organisms. Since no air can enter, new micro-organisms cannot grow. This is used for juices, jams, sauces, and canned vegetables.

6. Adding Preservatives

Some harmless chemicals, called preservatives, are added to food to prevent the growth of micro-organisms. These are often used in packaged foods like jams, jellies, and squashes.

Think about it:

1. Why do pickles last for a very long time without spoiling?
2. How does a deep freezer help preserve food for many months?

Importance of Food Preservation

Food preservation is very important for several reasons:

• Reduces Food Waste: It helps us save food from spoiling, ensuring that more food is available for consumption. This is crucial for 'Food for All'.
• Availability Throughout the Year: It allows us to enjoy seasonal fruits and vegetables even when they are not in season.
• Food Security: By preserving food, we can store it for future use, which helps in times of scarcity or emergencies.
• Economic Benefit: Farmers and businesses can sell their produce over a longer period, reducing losses.
• Safety: Proper preservation methods ensure that the food we eat is safe and healthy.

What’s the solution?

Your family has a lot of fresh mangoes during the summer season. You want to enjoy mangoes even in winter. What methods of food preservation can you use?

Always remember: Preserving food helps us make the best use of our food resources and ensures that nutritious food is available for everyone.

What We Have Learnt

• Food spoils due to the growth of micro-organisms, which thrive in moisture and warmth.
• Various methods of food preservation are used to prevent spoilage.
• Common preservation methods include drying, cooling, boiling, pickling, canning/bottling, and adding preservatives.
• Food preservation is important to reduce waste, ensure year-round availability, contribute to food security, and maintain food safety.

Exercises

1. Fill in the blanks.
   1. Food spoils faster in __________ temperatures.
   2. Removing moisture from food is called __________.
   3. Boiling milk helps to kill __________.
   4. Salt and sugar are used in __________ to preserve food.
2. Answer the following questions.
   1. Why does food spoil?
   2. List any three methods of food preservation.
   3. How does refrigeration help preserve food?
   4. What are two reasons why food preservation is important?
3. Match the following:

   Column A	Column B
   1. Drying	a. Keeping food in the fridge
   2. Cooling	b. Making pickles
   3. Pickling	c. Removing moisture from food

Activities

1. Observe different food items in your kitchen and discuss with an elder how they are preserved.
2. Visit a local market and identify different types of preserved foods.
3. Prepare a simple preserved food item (e.g., sun-dried tomatoes or a simple pickle) with adult supervision.