Malt-induced premature yeast flocculation: current perspectives

  • Apostolos G. Panteloglou
  • Katherine A. Smart
  • David J. CookEmail author


Premature yeast flocculation (PYF) is a sporadic problem for the malting and brewing industries which can have significant financial and logistical implications. The condition is characterised by abnormally heavy (and sometimes early) flocculation of yeast during brewery fermentations. The resulting low suspended yeast cell counts towards the end of the fermentation can result in flavour defects and incomplete attenuation (fermentation of sugars to alcohol). Despite several decades of research into the phenomenon, its precise nature and mechanisms have not been fully elucidated. In part this is because the term PYF has become a ‘catch-all’ syndrome which can have multiple origins. Furthermore, there are complex interactions in the malting and brewing processes which together mean that the PYF status of a malt sample is hard to predict at a generic level. Whether or not PYF is observed depends not only on barley quality, but on process factors in the maltings and to a substantial extent on the brewing yeast strain concerned. This article highlights the significance of PYF, and reviews current knowledge relating to the origins of this complex phenomenon.


PYF Brewing Fermentation performance Yeast flocculation Malt quality 



Premature yeast flocculation


A premature yeast flocculation positive sample (barley, malt or wort giving rise to PYF)


A premature yeast flocculation negative sample (control barley, malt or wort sample yielding normal flocculation characteristics)


Non-specific lipid transfer protein


Terminal restriction fragment length polymorphism



The authors would like to thank the UK Home Grown Cereal Authority for financial support. Professor Katherine Smart is the SABMiller Professor of Brewing Science and gratefully acknowledges SABMiller for their continued support.


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Copyright information

© Society for Industrial Microbiology and Biotechnology 2012

Authors and Affiliations

  • Apostolos G. Panteloglou
    • 1
  • Katherine A. Smart
    • 1
  • David J. Cook
    • 1
    Email author
  1. 1.Brewing Science Section, Division of Food SciencesThe University of NottinghamLeicestershireUK

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