Food spoils when it gets old. This is because food contains bacteria which is invisible to the naked eye. Over time bacteria grows and changes proteins and other substances found in food. When that happens, we can say that the food is spoilt.
Why does spoilt food make us feel ill if we eat it?
As already mentioned, bacteria in food rises over a period of time. Eating food with a lot of bacteria in it can give a stomach ache, or even cause loose motions. Also when bacteria breaks down, it can produce harmful substances which can make us very ill.
Bacteria are useful?
Bacteria can be useful too.
For example, bacteria breaks down the ingredients of milk to make yoghurt and cheese.
Bacteria are unicellular micro-organisms that are found almost everywhere. Although most bacteria are harmless to people, the build-up of certain varieties can lead to food poisoning. Beneficial effects of bacterial action include breaking down organic waste, producing antibiotics and making various food.
Take a piece of bread and leave it in a closed jar or outside for a few days and see what happens. Write down 10 places where you would find bacteria in your home and cross check with friends or family. How does a refrigerator help in storage of food?