B. M. TITUS (1), A. Oberholster (1);
(1) UC Davis, Davis, CA, U.S.A.
Technical Session 11 - Flavor and Product Stability II
Wednesday, June 17
1:00–2:15 p.m.
Fiesta 3,4,6,8
The phenolic profiles of barley, hops, and beer have been quantified in past research and their interactions with flavor-active compounds in beer has been documented by many researchers, but this work is far from exhaustive. Little is known about the composition of the compounds that influence the antioxidant behavior of hops and beer. Very few studies have documented the extraction of hop-derived compounds specifically during dry-hopping while monitoring the effects of this process on beer flavor stability. It is important to understand the origins of antioxidant compounds in beer as they have been shown to contribute significantly to beer quality and stability over time and they prevent the deterioration of flavor-active compounds in beer. Control of the concentration of these compounds in beer can not only increase the shelf life of the beer, but it can also have significant effects on the colloidal stability of the beer. The combined positive effect that polyphenols exhibit on beer flavor stability and the potential negative effect on colloidal stability make them a dichotomous set of compounds that require careful consideration. The objectives are 1) to determine the impact of dry-hopping on the flavor stability of beer in relation to polyphenol extraction; and 2) to determine the extraction rates of hop-derived flavor-active compounds during dry-hopping. The methods used include beer brewing: all experimental beers will be brewed at the August A. Busch III pilot brewery on the UC Davis campus in Davis, CA, and dry-hopped for a duration of up to 4 days. Iso-α-acid analysis: modified SPE-HPLC/DAD analysis as described in Jaskula et al. (2007). Polyphenol analysis: SPE-HPLC/DAD analysis as described in Dvořáková et al. (2007). Carbonyl analysis: modified HS-SPME/GC-MS analysis as described in Saison et al. (2008). Descriptive analysis: sensory analysis will be performed on selected treatments by a trained panel of 15 individuals. Analysis will be done on fresh beer and on the same beer aged for 2–3 months. This research is in progress. The results of this original research will provide data increasing our understanding of the extraction of flavor-active compounds during the dry-hopping process. A positive correlation of chemical and descriptive analyses will provide strong evidence of the preservative effects that hop-derived polyphenols contribute to beer as well as build on the current body of research in the fields of polyphenols and beer flavor stability. This research will provide the industry with a better understanding of the contribution made by polyphenols to beer flavor while elucidating the role of the dry-hopping process in flavor stability. As breweries continue to employ the dry-hopping process for a growing number of their beers, the importance of research in the field of hop chemistry increases.
Brad Titus is a graduate student working toward an M.S. degree in the field of agricultural and environmental chemistry at the University of California, Davis. His research focuses on hop chemistry and beer flavor stability, and he is currently working under Anita Oberholster. Brad also completed his B.S. degree at UC Davis in food science and technology, with an emphasis in brewing. He has been involved in the Food Science Brewing Club at UC Davis as an officer since the club’s inception.
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