Foods, especially perishable foods, may become spoilt as a result of lack of adequate storage, preservation or packaging. This leads to abnormal flavour, colour, odour or consistency, which may or may not be harmful.
In 1986, about one half of the European refrigerated surplus food stocks were no longer fit for consumption by human or animal.
When cooked foods cool to room temperature, microbes begin to proliferate. The longer they wait, the greater the risk. Cooked foods should preferably be eaten just as soon as they come off the heat. A common error in households, responsible for countless cases of foodborne disease, is putting too large a quantity of warm food in the refrigerator. In an overburdened refrigerator, cooked foods cannot cool to the core as quickly as they must. When the centre of food remains warm (above 10 degrees celsius) too long, microbes thrive, quickly proliferating to disease producing levels. It is also essential that reheating is done properly so that all parts of the food reach at least 70 degrees celsius.