摘要
Premature yeast flocculation(PYF)during beer fermentation is an undesired event by which yeast flocculate too early and heavily before the wort nutrition is exhausted.While PYF can be a major financial detriment to brewers,the conditions that trigger it and the chemical composition of PYF are poorly understood.Gas chromatography-mass spectrometry results from this study indicated that purified malt PYF factor consisted of numerous polysaccharides;however,no protein was identi-fied.High concentrations of PYF promoted further yeast flocculation,which in turn decreased the rate of fermentation and increased acetaldehyde content of the beer.PYF factors were found to be derived primarily from malt husks and factors such as microbial content of the water used for germination,mixing malts with different PYF values,and presence of tannic acid were all found to influence the rate of yeast flocculation.Findings from this study may be beneficial in developing PYF prevention and control measures that can be applied to future brewing strategies.
