9.17: rate of decomposition in food preservation

What conditions are required for decomposition?

High temperature, water and high availability of water

How can temperature affect the rate of decomposition?

Chemical reactions generally work faster in warmer temperatures - however, if it is too hot, the enzymes can denature and stop decomposing

We keep food in the fridge because lower temperatures mean that there is a slower rate of decomposition, so the food lasts for longer

How can water content affect the rate of decomposition?

Microorganisms grow faster in conditions with a high water content as it is required for respiration, and makes food easier to digest

By removing all of the water from food (such as freezing the food, which turns the water into ice), the rate of decomposition stops since decomposers cannot survive without water

How does the availability of oxygen affect the rate of decomposition?

Most decomposers require oxygen as they respire aerobically. If decomposers do not have access to oxygen, they will not be able to grow or multiply, although some decomposers can survive without oxygen.

By sealing food in bags or cling film, we are removing the air supply from the food and making it last for longer

How can the rate of decay be measured?

Changes in pH (eg in milk), change in mass (decaying food) or change in temperature (grass cuttings)