Catabolism of Amino Acids in Cheese during Ripening

Abstract

This chapter discusses the process of catabolism of amino acids in cheese during ripening. Catabolism of amino acids plays a major role in flavor development in cheese during ripening. In particular, the catabolism of sulphur-containing amino acids (principally methionine), aromatic amino acids, and branched-chain amino acids to flavor, or perhaps off-flavor, compounds has received considerable attention. There appear to be two major pathways by which amino acids are catabolized. The first series of reactions is initiated by the action of an aminotransferase, which transfers the amino group from amino acid A to an α-keto acid B (usually ot-ketoglutaric acid) and results in the production of an α-keto acid corresponding to amino acid A and a new amino acid corresponding to α-keto acid B, α-Keto acids produced by the transamination of aromatic amino acids, branched-chain amino acids and methionine may be degraded further to other compounds by enzyme-catalyzed reactions or by chemical reactions. The second major series of reactions by which amino acids are catabolized is initiated by the action of amino acid lyases, which cleave the side chains of amino acids. These pathways are particularly important for the catabolism of aromatic amino acids and methionine. Other pathways by which amino acids may be catabolized include the production of amines by decarboxylases and the production of NH3 by deaminases. There are also specific pathways for the metabolism of threonine, aspartic acid, glutamic acid and arginine. The chapter also discusses their importance to cheese flavor, the catabolism of methionine, branched-chain and aromatic amino acids.