Mighty Microbes

Food undergoes changes that makes it spoilt.  These changes can be detected by their smell, taste, touch or sight.  Spoilt food is unsafe to eat.

Fish is no longer fresh when the flesh has changed texture.  It is no longer firm when pressed with a finger.  It also has an unpleasant smell.  

Stickiness under the chicken wings and darkening of their tips indicate spoilage.

We are blessed with many varieties of food.  However, our food may be infected with microorganisms.  Microorganisms such as fungi and bacteria can cause food to spoil.


The fruit and vegetables in the picture have been affected by moulds.  They become mouldy and change colour.

Food turns sour because the bacteria in it produced acids.  A common example is when milk turns sour, giving it an unpleasant taste.


It is possible for drinks in cartons to spoil.  When it is opened, frothy liquid and an unpleasant smell will indicate spoilage.


There are certain conditions that make this happen.  Microorganisms that cause food to spoil need air, water, nutrient, suitable temperature and suitable acidity to grow and multiply.

Microorganisms need air and nutrient to grow.  They grow on the surface of food when air is present.  The food provide nutrient for them.

Microorganisms also need water to survive.  Water in the food and moisture provide suitable environment for bacteria and fungi to grow.

Microorganisms will grow within a range of suitable temperature, which is between 5°C and 65°C.  They will grow slowly or not at all when the temperature is too high or too low.  Similarly, they also need a range of suitable acidity present on the food in order to grow.