The Bio Brief

Food preservation means preventing food from spoiling.
Food spoils mainly because of the growth of microorganisms.

Signs of Spoiled Food

• Bad smell
• Bad taste
• Change in colour
• Rotten appearance

Food + Microorganisms

        ↓

     Spoilage

So, food preservation helps to protect food from microorganisms and keep it safe for a longer time.

Why Does Food Spoil?

• Microorganisms grow on food
• Moist and warm conditions help microbes grow faster
• Spoilage of food is a chemical change

Methods of Food Preservation

1. Chemical Method (Preservatives)

Some chemicals stop the growth of microorganisms. These are called preservatives.

Common preservatives:

• Salt
• Sugar
• Edible oils
• Vinegar
• Sodium benzoate
• Sodium metabisulphite

Used in:

• Pickles
• Jams
• Squashes

2. Preservation by Common Salt

• Salt removes moisture from food
• Microorganisms cannot grow without water

Food + Salt

     ↓

Less moisture

     ↓

No growth of microbes

Used to preserve:

• Meat
• Fish
• Amla
• Raw mango
• Tamarind

3. Preservation by Sugar

• Sugar reduces moisture content
• Prevents growth of bacteria

Food + Sugar

     ↓

Reduced moisture

     ↓

Food preserved

Examples:

• Jams
• Jellies
• Squashes

4. Preservation by Oil and Vinegar

• Oil and vinegar create conditions where microbes cannot survive

Pickle + Oil/Vinegar

        ↓

Microbes cannot grow

Used for:

• Pickles
• Vegetables
• Fruits
• Fish
• Meat

5. Heat and Cold Treatments

Boiling (Heat Treatment)

• Boiling kills microorganisms
• Example: boiling milk

Milk + Heat

     ↓

Microbes killed

Refrigeration (Cold Treatment)

• Low temperature slows down microbial growth
• Food stays fresh for a longer time

Food in refrigerator

        ↓

Slow growth of microbes

Pasteurisation of Milk

Pasteurisation is a special heat treatment of milk.

Steps of Pasteurisation:

Milk

 ↓

Heated to 70°C (15–30 seconds)

 ↓

Suddenly cooled

 ↓

Stored safely

• Discovered by Louis Pasteur
• Pasteurised milk does not spoil quickly
• Can be consumed without boiling

6. Storage and Packing

• Food is stored in air-tight packets
• Prevents entry of microorganisms and air

Food sealed in packets

          ↓

Protected from microbes

Examples:

• Dry fruits
• Vegetables
• Snacks

Food preservation:

• Prevents spoilage
• Stops growth of microorganisms
• Increases shelf life of food
• Keeps food safe and fresh