Many microbes, called proteolytic, can digest proteins, but most can't. The choice of peptone is sometimes of importance. For example, for a positive hydrogen sulfide test, the medium must contain sulfur-containing amino acids. Tryptone is a tryptic digest of casein. Casein is a complex of proteins found in milk.
Trypsin is an important digestive enzyme produced by the pancreas.
It cleaves proteins into shorter pieces called peptones. Tryptic digests of dried milk are called tryptones. Tryptones are the best choice for bacteria media because they are used by most bacteria from animals and supply nitrogen, energy, and carbon. Tryptones are not pure substances. Tryptones are used in foods for flavoring and nutrition, in electroplating for smooth plating, and in media for microbes.