MBAA TQ https://doi.org/10.1094/TQ-55-3-0902-01 |
VIEW ARTICLE
Meagan Armstrong (1), Andrew J. MacIntosh (2), Maria Josey (1,3), and R. Alex Speers (1,3). 1. International Centre for Brewing and Distilling, Heriot Watt University, Edinburgh, U.K. 2. Department of Food Science and Human Nutrition, University of Florida, Gainesville, FL, U.S.A. 3. Canadian Institute of Fermentation Technology, Dalhousie University, Halifax, NS, Canada.
AbstractPremature yeast flocculation (PYF) has been shown to induce early and enhanced yeast flocculation and can result in a myriad of production difficulties and delays. Researchers have demonstrated that PYF is linked to fungal infection of barley and/or malt. Therefore, one might suspect that PYF occurrence would increase in wet climates. To test this hypothesis, a control, a PYF-positive malt sample, and two Scottish-sourced malt varieties were compared with a control dataset of 77 fermentations. Miniature fermentation trials using the ASBC method Yeast-14 were performed on these samples. Miniature fermentation trials have been optimized to detect PYF-causing malt by directly measuring attenuation via extract readings and indirectly measuring yeast in suspension via absorbance. Nonlinear and tilted Gaussian regressions were fit to the data sets to obtain attenuation and absorbance curves, respectively. Results obtained indicated that the PYF-causing malt induced both early and enhanced flocculation, whereas the other three malts (including the Scottish malts) did not induce early or enhanced flocculation. All four samples were compared using the F test, and it was determined that the PYF-positive malt sample was significantly different than the other three malts (
P < 0.05). Using previous results from 77 miniature fermentation trials on control malts, a novel 95% prediction band was developed. This band was applied and used to identify and decisively confirm the presence of PYF-causing malt as demonstrated herein.
Keywords: Premature yeast flocculation (PYF), PYF prediction band
