Yeast lipids and beer flavour.
The influence of the lipids of yeast on beer flavour is substantial because (a) the extent of sterol synthesis largely controls yeast growth and thus the many flavour attributes which are growth-related, and (b) freshly synthesised fatty acids may be excreted and impart caprylic flavour to beer. The control of sterol synthesis is discussed in relation to oxygen supply and pitching rate and the relationship between reduced sterol synthesis, reduced growth and "sticking" fermentations is considered. Close relationship is demonstrated between the content of C6-C10 fatty acids in beer and in yeast; the control of fatty acid synthesis in yeast by oxygen is shown to regulate caprylic acid contents in beer.
Keywords: beer brewing fatty acid flavour lipid oxygen Saccharomyces steroid yeast