This refers to damage to food that is caused by micro organisms (bacteria, moulds and yeasts). Micro organisms can grow in almost all kinds of food products. As micro-organisms occur everywhere around us, there is always a risk of microbial spoilage.

There are thousands of kinds of micro organisms, most of which can grow in a variety of products under the right conditions. The growth is dependent of the kind of food, the type of micro organism, the temperature and other factors.

Dry products such as bread and cookies do not have enough moisture to allow bacterial growth. Spoilage to these products is usually caused by moulds.

Sour, salted or sugary products do not provide good growth environments for most micro organisms. They can be harmed by specific spoilage flora that have adapted to them.

Most micro organisms are not dangerous. A spoiled product is not necessarily dangerous, but it can taste bad. For safety, it is best not to eat spoiled products.