Q.

1. Why is food stored for a long time ?
2. What methods are used for preservation of food ?
3. What is meant by quality of food ?

Step 1. Why store food long-term. Fresh food (grain, fruit, milk, meat) is produced or harvested only at particular times or places, but it needs to be consumed over a much longer period and often far from where it was produced -- storage is what bridges that gap.

Step 2. What preservation methods do. Preservation works by slowing or stopping the chemical/enzymatic and microbial processes that spoil food: minimising oxygen exposure (airtight containers, vacuum packing, or filling with N2 gas), lowering temperature (refrigeration, which slows reaction rate), and heat treatment (boiling, which denatures the enzymes responsible for spoilage reactions such as browning). …

Direct recall of the storage/preservation/quality framing given at the sta …

• Describing preservation only as 'refrigeration', missing that airtight/vacuum/N2 packaging and heat-denaturation of enzymes are equally valid, chapter-cited methods. …