LIPID METABOLISM AND THE REGULATION OF VOLATILE ESTER SYNTHESIS IN SACCHAROMYCES CEREVISIAE

Abstract

The specific rates at which ethyl acetate and iso‐amyl acetate are produced by yeast increase markedly at that point in fermentation where syntheses of lipids (i.e. saturated fatty acids and squalene) stop. An increase in the acetyl‐CoA: CoASH ratio, or a reduced availability of substrates (fatty acyl‐CoAs) for acyl transferases, are possible reasons for such a stimulation of ester synthesis. Increased rates of ester production are not sustained but contribute significantly (ca. 30% for ethyl acetate) to the total concentration of acetate esters in beer fermented from 1·040 all‐malt wort. Addition of linoleic acid (50 mg litre−1) suppresses the induction of ester synthesis and reduces overall formation of both ethyl and iso‐amyl acetates by ca. 80%. Possibly, linoleic acid exerts these effects either by directly inhibiting the activity of an ester‐synthesising enzyme, or by allowing alternative use of acetyl‐CoA for the synthesis of saturated fatty acids. 1982 The Institute of Brewing & Distilling