Technical Session 03: Yeast I Session
Urs Wellhoener, Boston Beer Company, Boston, MA, USA
Co-author(s): Annette Fritsch, Boston Beer Company, Boston, MA, USA
ABSTRACT: There are a variety of factors that indicate maturity based on the beer system, and the identification of a mature sample is based on the beer itself, particularly fermentation by-products, dry hopping, and spicing. Commonly, the main focus is from the analytical perspective. This includes parameters like diacetyl or acetaldehyde. However, what other factors designate the right maturation time, primarily after active fermentation is complete and the beer is in basically “static” storage? In this study, a spiced, lager beer was evaluated during storage using both chemical analysis for a wide range of fermentation by-products and sensory descriptive analysis. Similar to dry-hopping, the aroma and flavor impact of spices unfold depending on interactions with other compounds in the beer. The synergies and inhibitions among compounds change during maturation. Therefore, it was essential to evaluate how the impact of spices changes during storage. Analysis techniques including ANOVA and PCA were applied to both the chemical and sensory data to determine the optimal maturation time. In addition to identifying optimal maturation, the level of yeast carry over into static storage was explored. A moderate yeast carry-over is desired to help the beer to mature further (e.g., diacetyl) but should be kept minimal to minimize yeast autolysis, which can affect beer aroma/flavor and foam negatively. Since the beer in this study was “completely end-fermented,” prior to hitting the storage tanks, the question of whether yeast should be removed completely via centrifugation at fassing was addressed as well. Through a combination of analytical techniques, we were able to identify both the impact of storage on a spiced lager beer and the effect of varying levels of yeast carry-over on the storage profile. A panel of sensory experts rated the maturity of the beer according to attributes like overall maturity, spice, diacetyl, acetaldehyde, etc.
Urs Wellhoener, the corporate manager for yeast and fermentation for the Boston Beer Company, joined the company in October 2007. His focuses are yeast management and microbiology. He is a technical graduate as a brewer and maltster (1991–1993) and received a Dipl.-Eng. degree from the Faculty of Brewing and Food Technology of the Technische Universität München-Weihenstephan (TUM) in 1999. After graduation in 1999 he was a project manager on a yeast project at Veltins Brewery, Meschede-Grevenstein (1999–2000). Between 2000 and 2007 Urs was a scientific assistant and doctorate at the Chair of Brewing Technology II at the Weihenstephan Center of Food and Life Sciences, Technische Universität München-Weihenstephan (TUM). He received his Ph.D. degree for his studies on yeast physiology during fermentation and propagation. During this time he also worked for Muellerbraeu, Pfaffenhofen/GER, as QC manager.