Enzymes are protein molecules that are present in all living things. They speed up and target chemical reactions, in many cases increasing the rate of reaction millions of times. For example, they aid digestion, metabolise and eliminate waste in humans and animals, and play a crucial role in muscle contraction.

Enzymes have been used unknowingly in food production, e.g. dough making, for centuries. They can be obtained by extraction from plants or animals or by fermentation from micro-organisms. They are usually purified but may contain varying traces of the other naturally occurring constituents of these three sources. They are normally added to perform a technological function in the manufacture, processing, preparation and treatment of foods. Examples include enzymes used to break down the structure of fruit so that manufacturers can extract more juice, or to convert starch into sugar in alcohol production.

Historically enzymes are considered to be non-toxic and not of safety concern for consumers since they are naturally present in ingredients used to make food. However, food enzymes produced industrially by extraction from plant and animal tissues, or by fermentation of microorganisms, are assessed for safety.