Bromelain is a protein extract derived from the stems of pineapples, although it exists in all parts of the fresh plant and fruit. The extract has a history of folk medicine use. As a culinary ingredient, it may be used as a meat tenderizer. Bromelain extract is a mixture of protein-digesting (proteolytic) enzymes or proteases, and several other substances in smaller quantities. The proteolytic enzymes are sulfhydryl proteases, since a free sulfhydryl group of a cysteine side chain is required for function.