Preservation of Food

Shelf life

Step 1: 'Shelf life' is the technical term used to describe the length of time food remains fresh and safe to eat. Step 2: On packaged food items, shelf life is indicated as 'Best Before' or 'Consume Before' a specified date. Step 3: After this date, the food may not look, taste, or be as safe as when it was fresh. Step 4: Expiry date is a related but different term — shelf life refers to the period of freshness, while expiry is the date after which the product should not be used. Step 5: Food items are classified as perishable, semi-perishable, and non-perishable based on their shelf life.

Whole grain cereals and pulses

Step 1: Foods are classified into three types based on shelf life — non-perishable, semi-perishable, and perishable. Step 2: Non-perishable foods are those that take a very long time to spoil. Examples include whole grain cereals, pulses, nuts, oil seeds, sugar, and jaggery. Step 3: Perishable foods spoil quickly and include green leafy vegetables, tomatoes, bananas, bread, and butter. Step 4: Semi-perishable foods last longer than perishable but shorter than non-perishable — examples include eggs, potatoes, onions, biscuits, and cakes. Step 5: Whole grain cereals like rice and wheat can be st

A process that prevents food from spoiling and retains its colour, taste, and nutritive value

Step 1: Food preservation is defined as a process by which food items are prevented from getting spoilt for a short or long period of time. Step 2: An important part of this definition is that preservation also aims to retain the colour, taste, and nutritive value of food as far as possible. Step 3: Option A is wrong — cooking at high temperature alone is just one method and is not the complete definition of preservation. Step 4: Option C is wrong — bulk buying is storage, not preservation. Step 5: Option D is wrong — dehydration removes moisture but preservation is a broader concept covering

Killing micro-organisms by raising temperature

Step 1: There are three main principles of food preservation — killing micro-organisms, preventing/delaying their action, and stopping enzyme action. Step 2: When milk is boiled, the high temperature kills the micro-organisms present in it. Micro-organisms cannot survive at very high temperatures. Step 3: Boiling also stops the action of enzymes present in milk, which further extends its shelf life. Step 4: Option A is wrong — lowering temperature (refrigeration) delays but does not kill micro-organisms. Step 5: This is why we boil milk at home before drinking it — it makes the milk safe by ki