(a) What is meant by food preservation? Name any five methods of preserving food. (b) How do you preserve cooked food at home?

Food preservation refers to the treatment and handling of food to prevent spoilage caused by microorganisms (bacteria, yeasts, molds), slow down enzyme activity, and maintain nutritional value, texture, flavor, and safety for extended periods beyond normal shelf life. Since ancient times, humans have developed preservation methods to ensure food availability during seasons of scarcity, reduce waste, enable long-distance transportation, and prevent foodborne illness. Five major preservation methods include: refrigeration and freezing (low temperatures slow microbial growth), canning and heat processing (high temperatures kill microorganisms and create sealed environments), drying and dehydration (removing moisture that microbes need), chemical preservation using salt, sugar, vinegar, or food preservatives (creating unfavorable conditions for microbial growth), and pasteurization (controlled heating to kill pathogens while maintaining food quality).

At home, cooked food is primarily preserved through refrigeration and freezing. Refrigeration at temperatures below 5°C significantly slows bacterial growth, extending the safe storage period of cooked foods for 2-4 days depending on the food type—store food in clean, covered containers immediately after cooling to room temperature. Freezing at -18°C or below stops microbial growth almost completely, preserving cooked meals for weeks or months without significant quality loss. Additional home preservation practices include storing cooked food in airtight containers to prevent contamination and moisture loss, reheating food thoroughly before consumption to kill any bacteria that may have multiplied during storage, and practicing "first in, first out" rotation to use older stored food before newer batches. Avoid repeated heating and cooling cycles, never leave cooked food at room temperature for more than two hours, and always smell and visually inspect stored food before consumption to detect spoilage.