P-17
Removal of hydrophobic components from beer by synthetic resins—Positive influence on flavor stability of beer
Presenter: Chikako Shimizu, Sapporo Breweries Ltd., Yaizu, Shizuoka, Japan
Co-Authors: Yasuhisa Kikuchi and Masachika Takashio, Sapporo Breweries Ltd., Yaizu, Shizuoka, Japan

The reduction of aging compounds and their precursors is an effective method for improving the flavor stability of beer. For this, we hitherto reported carbonyl reduction by yeast during fermentation and anti-oxidative mashing. For the same purpose, we examined the use of commercial synthetic resins and ion-exchange resins in the filtering process. Using an excessive amount of synthetic resins, the beer flavor would fade away (all the way, and become water-like). Furthermore, we have to be careful about losing hop bitter acids due to absorption. Therefore, we investigated the conditions under which the flavor and taste of fresh beer would be nearly equivalent to the control beer (no use of resin). The aim of this research was not only to improve flavor stability, but also to know by how much removing components with resins can have a discernible effect on sensory analysis. First, we examined the properties of resins in small-scale experiments and selected several resins for further testing (e.g., HP20, XAD4). The results of an HPLC analysis using an ODS column showed that the hydrophobic peaks were dominantly absorbed by the resins. Next, using 30-L filtration equipment, we filtered beer and Happoshu using two or three kinds of the resins (0.2 g wet resin/100 ml) with regular filter aids. Bitterness units (0.9 - 7.1), beer color (0.1 - 0.8 EBC), and polyphenols (9 - 33 mg/L) in the filtrated beers were absorbed by the three resins. The sensory tests of fresh beers showed no significant difference between the control beer and the resin-filtered beers. However, after storage at 37°C for one week or at 30°C for one month, there were statistical differences (p < 0.05) in the caramel-like flavor or papery flavor. The influence of the resins on the whiskey-like flavor was smaller than that of the other flavor profiles. After storage at 37°C for one week, the differences in trans-2-nonenal between the control and test beers were 0.02 - 0.07 ppb, and after storage at 30°C for one month, the differences were 0.02 - 0.06 ppb. Strecker aldehydes were decreased by about 5 - 25% by absorption before storage. Some Maillard compounds such as 5-HMF and furfural were only slightly affected by absorption. There are a lot of indices for the flavor stability of beer, but most of them exist under the threshold level in beer. We could not determine aging compounds in this experiment, but could guess that the multiplier effect of a great number of compounds constitutes the aged flavor. From these results, we believe that selective absorption of hydrophobic components from beer by using a resin treatment should improve the flavor stability. The development of synthetic resins might be one of a workable alternative for ensuring flavor stability.

Chikako Shimizu received the Ph.D. in medicinal chemistry from the Shizuoka College of Pharmacy in 1990. She joined the Pharmaceutical Research Laboratory of Sapporo Breweries Ltd. in 1990, and moved to the Brewing Research Laboratory in 1993. She researched the effect of proteinase A on beer foam stability, new products development, the relationship between the ploidy of brewing yeast and its metabolism, and the flavor stability of beer with special interest in carbonyl reduction by yeast. She is currently engaged in planning of research in the Frontier Laboratories of Value Creation of Sapporo Breweries Ltd.