Why food spoils
Fresh food does not stay fresh forever. Tiny living things called microorganisms, such as bacteria and mould, land on food and make it go bad. They grow fastest in places that are warm and wet, so food left out on a hot day spoils quickly.
Key idea
Food preservation slows down microorganisms so food stays safe to eat for a longer time.
Ways to preserve food
- Cooling and freezing keep food cold so microorganisms grow slowly.
- Drying removes water, and microorganisms cannot grow without water.
- Salting and adding sugar pull water out and stop them growing, like in salted fish or fruit jam.
- Bottling and pickling use vinegar to keep food sour and safe.
- Canning seals food in airtight cans after heating.
People long ago dried fish and meat in the sun so it would last through times when fresh food was hard to find. Today we still use these old ideas together with fridges and freezers. When we preserve food, less food is thrown away, so we waste less money and help the environment too.
Remember
- Preserving food means less waste.
- A bad smell, mould or slime means food has spoiled.
- Never eat food that looks or smells wrong.