Cheese flavour formation by amino acid catabolism

Amino acid catabolism is a major process for flavour formation in cheese. The ability of lactic acid bacteria (LAB) and other cheese micro-organisms to degrade amino acids to aroma compounds is highly strain dependent. Generally, amino acid catabolism proceeds by 2 different pathways. The first one, mainly observed for methionine, is initiated by elimination reaction and leads to major sulphur aroma compounds. The second pathway is generally initiated by a transamination reaction and is the main pathway for degradation of all amino acids by LAB. The resulting alpha -keto acids are then degraded to various aroma compounds via I or 2 additional steps. The lactococcal enzymes initiating both pathways have been well characterised, and their importance in the formation of aroma compounds has been demonstrated by using isogenic strains lacking each enzyme. From the new knowledge several applications have been successfully developed, especially for intensifying or diversifying cheese flavour by controlling amino acid transamination. (C) 2001 Elsevier Science Ltd. All rights reserved.