The phenomenon of premature yeast flocculation (PYF) is suspected to be caused (at least in part) due to fungal infection of barley. This study reports on an ongoing investigation that has identified a link between fungal pathogens and PYF behavior. Two varieties of barley, AC Metcalfe and CDC Bold, were exposed to each of three common barley fungal pathogens (Pyrenophora teres, Cochliobolus sativus, or Fusarium graminearum) and evaluated for PYF behavior during fermentation. Barley was infected in the field between flowering and grain maturation. Each sample was micro-malted, mashed, and fermented using a moderately flocculent yeast strain (SMA). Fermentations were performed using the ASBC "Miniature Fermentation" assay (ASBC Yeast-14) developed to detect PYF and assess fermentability or yeast strain performance. In order to detect evidence of PYF behavior, the absorbance at 600 mu of fermenting wort was used to assess yeast in suspension (turbidity). When infected with C. sativus and F. graminearum, the turbidity profile differed significantly (P < 0.01) between control and infected samples for both varieties of barley malt. The nature of the disparity was indicative of PYF behavior. Among malts that exhibited PYF, excess FAN was also observed. This is the first report demonstrating PYF behavior resulting from infection with these pathogens.

Malt barley breeders and maltsters often strive to improve the quality of their product by improving fermentability. Small-scale assays are often used to assess the fermentability of wort produced from malt under standardized mashing techniques. However, anecdotal reports suggest that these assays have poor correlation with industrial fermentations in addition to inconsistency between assays. There are several factors that are likely to contribute to this behavior such as pitching rate, mashing regime, fermentation temperature, barley modification, and batch size. This study aimed to isolate and examine the effect of fermentor size on wort fermentability through the use of miniature-scale (15 mL) assays fermented in parallel to industrial sized operations. These miniature fermentations were conducted at identical temperatures to their industrial scale counterparts and used oxygenated wort mashed and pitched by local craft breweries. Wort density was measured throughout the fermentations using a portable densitometer while the turbidity was assessed via spectrophotometer at 600 nm. It was found that fermentation vessel size had a significant effect on the apparent degree of fermentation; however, observed disparities were consistent between the assay and fermentor dimensions. For example, a difference in final density of 1.1 +/- 0.2 degrees P was observed between the final density of a 19.6 hL craft brewery and the miniature fermentation assay over three consecutive experiments. However, when the wort from an 8.5 hL brewpub was tested using this lab assay, no significant differences in final attenuation were found (P > 0.05). The shear generated through consumption of sugar and subsequent production of carbon dioxide was theoretically determined for each fermentation. A reduced shear generated within the shorter (miniature scale) fermentors likely influenced the yeast floc distributions and subsequent final density.