Baillo, A. J.1, Ley, A.1 and Brigham, M.1, (1)Melvin Brewing, Alpine, WY, USA
Technical Session 9: Hops II
Wednesday, June 07, 2017
10:15–11:30 a.m.
Harbourview (1st Floor)
Dry-hopping beer is desirable to isolate the herbaceous, green, fresh hop aroma associated with American India pale ales. Before dry-hopping and after a beer is fully attenuated, most amino acids present in the wort have been assimilated by yeast for the purpose of making proteins. In a nutrient-depleted environment yeast may be forced to autonomously produce amino acids. One such amino acid, valine, when biosynthesized relates to the production of diacetyl, a vicinal diketone (VDK). Heightened concentrations of diacetyl, 40–70 ppb, have been observed in dry-hopped beers at 68–70°F after rousing the yeast from the bottom of the vessel. In addition, the apparent attenuation decreases 0.1°P/day, while the cells in suspension increase. These data support the hypothesis that secondary fermentation is occurring in agitated and dry-hopped beers. Lowering the temperature of the fermentation to 60°F before dry-hopping promotes yeast flocculation and, after rousing the pellets, subdues the increase in VDK concentration, while reducing the decline in the apparent extract. Interestingly post–dry-hopping, we consistently observe an increase in gravity of approximately 0.1–0.2°P, regardless of the temperature at the time of dry-hopping. Understanding the enzymatic activity would elucidate the mechanism of the hypothesized secondary fermentation. With increased hop loads and 18% more craft breweries from 2014 to 2015 that do not have the lab power to study secondary fermentation, understanding the effects of dry-hopping will allow for greater process control and the ability to increase accuracy in projected production schedules.
Andrea Baillo is the former QA manager of Maui Brewing and is currently the QA manager of Melvin Brewing.
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