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MBAA TQ http://dx.doi.org/10.1094/TQ-53-1-0302-04  |  VIEW ARTICLE
Brewing Fundamentals, Part 3: Yeast Settling – Flocculation

Alex Speers. International Centre for Brewing and Distilling (ICBD), Heriot-Watt University, Riccarton, Edinburgh, Scotland, EH14 4AS.

Abstract
Toward the end of a brewing fermentation, a yeast culture must be effectively removed from the fermented wort by flocculation, centrifugation, or filtration after the culture has fulfilled its metabolic role. There are a number of factors that affect yeast flocculation. These factors include a strain’s genetic background, the structure of the yeast cell surface, particularly cell surface hydrophobicity, and wort composition. Malt-induced premature yeast flocculation (PYF) is a phenomenon whereby yeast flocculates out of suspension too early. PYF tends to occur sporadically but is still considered to be a recurring brewing problem. It is associated with certain batches of malt. The question “what exactly is PYF?” is still unanswered.

Keywords: Calcium ions, Cell wall structure, Fermentation, Flocculation, Premature yeast flocculation, Sedimentation, Wort