HYDROPHOBIC BEER PROTEINS AND THEIR FUNCTION IN BEER FOAM

Beer proteins were separated into four fractions by hydrophobic intera ction chromatography. The velocity of the increase in surface viscosit y (V(theta)) of the protein fractions was determined by model enrichme nt experiments using ultrafiltered beer. The highest V(theta) was obse rved in fraction H4, which was a mixture of hydrophobic beer proteins. V(theta) of the protein fractions was affected by the coexisting iso- alpha-acids; fraction H4 was found to form strongly hydrophobic comple xes with iso-alpha-acids. Fraction H4 was efficiently concentrated in beer foam during the process of manual pouring of beer. The quantitati ve analysis for proteins in 100 samples of domestic lager beer reveale d that there was a significant correlation between SIGMA value and fra ction H4 content. These results demonstrated that different proteins i n beer possess different hydrophobicity and surface-viscometric activi ty and that hydrophobic proteins play an important role in foam stabil ity.