Refrigeration helps in food preservation by

The correct answer is B. Refrigeration works by lowering temperature, which slows the rate of biochemical reactions in food. Spoilage needs microbial metabolism and enzyme activity, and both slow sharply at low temperatures. The rule of thumb is that reaction rates roughly halve for every 10 degrees Celsius drop, so the food keeps longer.

• A is wrong. Refrigeration is mainly bacteriostatic. It slows bacterial growth but does not kill most germs. Some psychrotrophic organisms keep growing in the cold, which is why refrigerated food still spoils eventually.
• C is wrong. Cold slows enzymes; it does not destroy them. Enzymes are denatured by heat, which is the principle behind blanching before freezing vegetables.
• D is wrong. A layer of ice is not the scientific basis of refrigeration. A vapour-compression or absorption cycle with a refrigerant produces the cold, and the ice layer is at most an old folk practice.

The core concept is temperature-dependent reaction kinetics. For Mains GS-III, link this to post-harvest losses, the cold chain for perishables, and FSSAI norms. Our food-processing and storage answers depend on this idea.

Trap: Many candidates pick A because "cold kills germs". Refrigeration only inhibits them; freezing and sterilisation are different processes.