Flavor Enzymes

The flavorese concept—enzyme definition in terms of a flavor produced—is only a first step in biochemical understanding of flavor-producing reactions. The substrate and product must be defined chemically, and frequently the latter must be identified from among many volatile compounds which possibly contribute to flavor. Three reasonably well-understood enzymatic flavor-producing reactions are: alliinase (S-alkylcysteine sulfoxide lyase), myrosinase (thiohydroximate-O-sulfate thioglycoside hydrolase), and the reactions producing aldehydes and alcohols from unsaturated fatty acids and amino acids. Possible biosynthetic pathways to the first two substrate types are discussed. Two instances of enzymatic destruction of undesirable flavors are debittering of grapefruit juice ("naringinase," a rhamnosidase plus a glucosidase) and removal of diacetyl from beer and orange juice (diacetyl reductase).