Esters and their biosynthesis in fermented dairy products: a review

Esters of short-chain fatty acids are aroma-impact compounds found in fermented dairy products. These esters are responsible for fruity flavours that can be regarded either as a defect or as an attribute by the consumer. An understanding of the mechanisms of ester biosynthesis will enable control of the development of fruity flavours in fermented dairy products. The biosynthesis of flavour-active esters in dairy systems proceeds through two enzymatic mechanisms—esterification and alcoholysis. Esterification is the formation of esters from alcohols and carboxylic acids, whereas alcoholysis is the production of esters from alcohols and acylglycerols or from alcohols and fatty acyl-CoAs derived from metabolism of fatty acids, amino acids and/or carbohydrates. Alcoholysis is essentially a transferase reaction in which fatty acyl groups from acylglycerols and acyl-CoA derivatives are directly transferred to alcohols and is the major mechanism of ester biosynthesis by dairy lactic acid bacteria and yeasts.