EFFECTS OF LINOLEIC ACID SUPPLEMENTS ON THE SYNTHESIS BY YEAST OF LIPIDS AND ACETATE ESTERS

Abstract

The concentrations of acetate esters in beer were reduced by up to 85% by addition of linoleic acid to the fermentation or by pitching with yeast previously enriched with this unsaturated fatty acid. Linoleic acid was rapidly incorporated into yeast lipids and was effective in reducing the rate of ethyl acetate formation within 2 h. Addition of linoleic acid altered the pattern of synthesis of fatty acids by yeast, causing a shift from medium toward long chain acids. Secondly, the amount of squalene in yeast was reduced by up to 70% whereas that of lanosterol was increased threefold. Since total yeast lipid synthesis was reduced by up to 40%, we conclude that less acetylCoA is synthesized in the presence of linoleic acid. Further, high concentrations of linoleic acid decreased the proportion of acetylCoA consumed by the synthesis of acetate esters. Therefore linoleic acid may directly decrease acetate ester synthesis in addition to its effect via reduction of acetylCoA availability.