S. Zhuang (1), A. Mott (1), K. Smart (2), C. D. POWELL (1); (1) University of Nottingham, Nottingham, U.K.; (2) SAB Miller, London, U.K.
Fermentation
Wednesday, June 4 - 10:00 a.m.-11:45 a.m.
Level 3, Crystal Room
Very high-gravity (VHG) fermentations of >20°P are increasingly attractive within the brewing industry to maximize process efficiency and as a means of cost and energy savings. However, the use of VHG worts can create issues during fermentation, particularly with regard to achieving the desired final product specifications. Detrimental effects can include longer fermentation times, altered flavor characteristics, and, in some instances, incomplete or inefficient conversion of sugars to ethanol. From the perspective of the yeast culture, the environment of VHG wort is considerably different than that of standard gravity. It is accepted that VHG conditions place increased stress on yeast; however, little is known regarding the precise impact of this on cellular activity. Here we report on the effect of wort gravity on yeast physiology, the functioning of the cell, and key fermentation performance indicators. The assimilation and utilization of available sugars will be explored, along with potential trade-offs under VHG conditions. We will also discuss the relationship between the extra demands placed on yeast metabolism and the generation of compounds that can be harmful to individual cells. In particular we describe the relationship between VHG fermentations and cellular redox potential, focusing on cellular damage caused by the production of reactive oxygen species (ROS) and the antioxidant response of cells. It is anticipated that the data generated and presented here will provide insight into some of the challenges faced by yeast in fermenting worts with particularly high sugar concentrations.
Chris Powell holds a Ph.D. degree on the subject of yeast cellular aging and fermentation performance from Oxford Brookes University (U.K.) and has occupied research positions at Bass Brewers (now Coors), and Lallemand (Canada). During his six years at Lallemand, Chris was responsible for R&D on the molecular characterization of micro-organisms utilized within the food and beverage industries, in addition to brewing yeast research. In 2010 Chris returned to the United Kingdom to take up a position as lecturer in yeast and fermentation at the University of Nottingham. Chris is presently involved in research in the areas of brewing science and also sustainable bioenergy. He is the author or coauthor of more than 40 publications and a regular reviewer for several scientific journals. Chris has served on the ASBC Technical Committee since 2005 (as chair since 2012) and on the ASBC Board of Directors since 2010. Outside of work, Chris spends a significant part of his time swimming, climbing, hiking, and exploring different parts of the world.
