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WBC Oral Presentation Abstracts
Oral Presentations Technical Session 1: Hops I
1. Influence of fermentation compounds from yeast on the quality of hop aroma. Presenter: Hitoshi Takemura, Kirin Brewery Company, Limited, Japan
Hop aroma is a very important factor that contributes to the flavor of beer; therefore, a great deal of care is taken to adjust hop aroma by controlling brewing parameters. Nevertheless, even when using the same hop variety under the same condi- tions (timing of addition and quantity), samples can have dif- ferent aroma intensities if fermentation is performed using different brewing conditions (temperature, yeast pitching rate, etc.). Therefore, we investigated the cause of differences in aroma intensities in order to facilitate more precise control of hop aroma. We had the following two hypotheses: “the extent of conversion of hop aroma by yeast varies according to the brewing conditions” (hypothesis 1), and “hop aroma is masked by compounds that are produced by yeast during fermenta- tion” (hypothesis 2). To test these hypotheses, samples that had different intensities of fruity aroma (lychee, citrus-like), even though the same hop variety (American Cascade and New Zealand Motueka) and hop addition conditions were used, were subjected to GC/MS analysis to determine whether there were any differences in the quantity of aroma compounds. The results indicated that the amount of linalool and the amount of beta-citronellol produced by the yeast did not significantly differ between the samples. This suggests that the validity of hypothesis 1 is low. Furthermore, as there was a difference in the amount of compounds that arise from fermentation, hy- pothesis 2 appears to be valid. Next, we investigated the influ- ence of esters and alcohols on hop aroma. We observed a ten- dency for alcohols (e.g., 1-heptanol) to mask fruity aromas. Therefore, we brewed samples in which cold wort from the same batch was fermented (in a 20 L scale fermentor) using different fermentation conditions. Sensory evaluations re- vealed differences in fruity aroma between samples. Statistical analysis indicated that there was a significant negative correla- tion between 1-heptanol and fruity aroma. Furthermore, 1- heptanol was positively correlated with the number of yeast cells added at the start of fermentation and fermentation tem- perature. These results further support hypothesis 2 and sug- gest that it is important to control fermentation conditions. The results of this research have lead to the establishment of spe- cific brewing conditions for more precise control of hop aro- ma.
Hitoshi Takemura has worked for Kirin Brewery Company Limited since receiving a master’s degree in life science from Kyoto University in 2002. He worked in the Quality Assurance Department of the Tochigi brewery for three years and then entered the Laboratory for Brewing, where he conducted research on the use of hops in wort boiling. From 2008 to 2010 he worked as a guest researcher in Lehrstuhl fuer Brau- und Getraenke Technologie fuer Technische Universitaet Muenchen. Since August 2010 he has worked in the Brewing Technology Development Center.
2. Hop aroma and harvest maturity. Presenter: Daniel Sharp, Oregon State University, Corvallis, OR, USA. Co- author(s): Yanping Qian, Shaun Townsend, and Thomas Shellhammer, Oregon State University, Corvallis, OR, USA.
Hop chemical composition changes, in particular aroma de- velopment, during plant maturation are part of a rapid and dynamic process that requires a comprehensive, in-depth chemical and sensory analysis to maximize characteristics of interest to brewers. The complex aroma chemistry associated with hops in beer has been a confounding variable for practical brewers, and a deeper understanding of hop aroma develop- ment during cultivation is needed. This presentation discusses results and conclusions from a two-year study and compares these results with other studies that have examined location and harvest time and their effect on brewing quality. The effect of harvest date and location on and a variety of key chemical components of Willamette and Cascade hops were investigated for the 2010 and 2011 growing seasons. Hops were harvested at three time points within a 3-week interval (early, normal, and late), from three different farms in the Willamette Valley, Oregon, and then analyzed for moisture, hop acids content, total oil content, and essential oil composition. The response of analytes was dependent on the variety being examined, its location within the Willamette Valley, as well as the time of harvest. Hop acids did not change appreciably during plant maturation, while hop oil content increased hyperbolically to a plateau as the hops aged on the bine. Increases in oil quantity were strongly correlated (r > 0.80) with increases in alpha- pinene, beta-pinene, myrcene, limonene, methyl heptanoate, linalool, and eudesmol concentrations. Growing location with- in the Willamette Valley had a significant effect on oil concen- trations for each variety at each time point, thus suggesting that individual grower practices and local environmental influ- ence hop chemical composition.
Daniel Sharp is a master’s student in the Food and Fermentation Science program at Oregon State University. His research is currently focused on hop studies being conducted in Thomas Shellhammer’s lab. Daniel’s primary area of study is the aroma compounds in hops and beer. Prior to joining the Food Science program at OSU, Daniel earned a B.A. degree in both Spanish and adventure leadership at the University of Oregon. After graduation he lived and worked in South America, first as a mountain guide in Venezuela and later as a brewer at the Center of the World Brewery, Ecuador’s only microbrewery at the time.
3. Phenolic profiling of lager beer during aging in relation to hopping technology. Presenter: Patricia Aron, MillerCoors, Milwaukee, WI, USA. Co-author(s): Thomas Shellhammer, Oregon State University, Corvallis, OR, USA; David Ryder, MillerCoors, Milwaukee, WI, USA.
The most important class of polyphenols for consideration in beer and related products is that of the 2-phenylbenzopy- rans, generally referred to as flavonoids. In contrast to the roles of other hop derived ingredients, such as the isomerized alpha-acids and their reduced products (bittering acids), the absolute value of hop derived flavonoids is not well realized. To add to the confusion, very little is understood regarding the fate of these polyphenols during the brewing and aging pro- cesses. During this experiment lager beers were produced us- ing varying hopping regimes to investigate hop product contri- bution to beer polyphenol content. Finished beers were also force-aged and monitored for changes in polyphenolic profiles. Polyphenol rich extracts were produced from the beers using Sephadex LH20 resin. Finished beers varied in total polyphe- nols, flavanoids, and proanthyocyanidins by hopping regime.
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