PRODUCTION OF AROMA COMPOUNDS BY YEAST

The yeast plasma membrane regulates the movement of compounds into the yeast cell and of yeast metabolites from the cell into the medium. The rate of penetration of organic acids into the yeast cell depends on their lipophilic nature, and on their molecular size and degree of branching. During fermentation yeast synthesizes a vast number of aroma compounds. The numerically and quantitatively largest groups of aroma compounds include fusel alcohols, fatty acids and fatty acid esters. The yeast used and the fermentation conditions can influence the formation of aroma compounds. The yeast also has a profound effect on the formation of other aroma compounds, such as sulphur compounds and phenols. In addition to fermentation, the maturing of a beverage can also influence the aroma. During the maturing lactones, phenols and other compounds are extracted from the oak casks in which the beverage is aged. The presence of the so‐called “whisky lactone”, β‐methyl‐γ‐octalactone, is characteristic of a beverage that has been matured in oak. 1979 The Institute of Brewing & Distilling