B3/ Further additional science

what affects the rate at which micro organisms grow?

Exponential growth

This is when bacteria cells divide a lot in a short period of time. In the right conditions bacteria can divide every twenty minutes. If milk has high levels of bacteria present in it, it could cause infections of the gut, such as food poisoning or other illnesses.

One way of testing the amounts of bacteria cells present in a sample is to use resazurin dye. This shows how quickly oxygen is used up. The more bacteria present, the quicker the quicker the oxygen levels fall. This is indicated because the dye will change from blue to a pink shade, and eventually cloudless as the oxygen levels fall.