Serial re-pitching: its effect on yeast physiology, fermentation performance, and product quality

BackgroundSerial re-pitching is a term given to a practice whereby yeast harvested at the end of fermentation is re-used in subsequent fermentations.PurposeThe purpose of this paper was to review and summarize existing literatures, research data, and case studies to illustrate the effect of re-pitching on the physiology and fermentation performance of brewing yeast and the resulting quality of beer.MethodsData related to biomarkers used to assess yeast physiology and fermentation performance and quality of beer were compared for various articles.ResultsAnd comparison of the results was done with caution as many of the studies were conducted using different yeast strains, wort gravity, pitching rate, and other fermentation conditions.ConclusionThis study confirms that serial re-pitchings aggravate the effect of pitching rate, wort gravity, cell age, yeast oxygenation, and yeast strain on yeast cell physiology, fermentation performance, and quality of final beer. However, further empirical research at molecular level is crucial.