Hydrophobic Beer Proteins and Their Function in Beer Foam. Shigehisa Yokoi, Kazuyuki Yamashita, Naoyuki Kunitake, and Shohei Koshino, Brewing Research Laboratories, Sapporo Breweries Ltd., Yaizu, Shizuoka, 425 Japan. J. Am. Soc. Brew. Chem. 52:0123, 1994.

Beer proteins were separated into four fractions by hydrophobic interaction chromatography. The velocity of the increase in surface viscosity (V_?) of the protein fractions was determined by model enrichment experiments using ultrafiltered beer. The highest V_? was observed in fraction H4, which was a mixture of hydrophobic beer proteins. V_? of the protein fractions was affected by the coexisting iso-α-acids; fraction H4 was found to form strongly hydrophobic complexes with iso-α-acids. Fraction H4 was efficiently concentrated in beer foam during the process of manual pouring of beer. The quantitative analysis for proteins in 100 samples of domestic lager beer revealed that there was a significant correlation between Σ value and fraction H4 content. These results demonstrated that different proteins in beer possess different hydrophobicity and surface-viscometric activity and that hydrophobic proteins play an important role in foam stability.

Keywords: Foam stability, High-molecular-weight proteins, Hydrophobic interaction chromatography, Hydrophobicity, Iso-α-acids, Surface viscosity