A New Method for Evaluating Foam-Damaging Effect by Free Fatty Acids

Abstract

The foam damaging effect (FDE) value of a free fatty acid, representing its extent of adsorption on a foam cell surface, is described. This FDE value is calculated using the surface excess, which is quantitatively measured by the excess surface concentration of solute in a bulk solution. The increase in FDE value following the addition of free fatty acid to a sample beer showed a high correlation with decreasing rate of foam thickness. The total FDE value of the free fatty acids showed a negative correlation with foam stability (the NIBEM value) for the tested beers, which were produced with the same malt ratio and fermentation conditions. Di- and trihydroxyoctadecenoic acids derived from linoleic acid were the decisive compounds that determined the total FDE value of the fatty acids in the tested beers. The addition of di- and trihydroxyocatedecenoic acids to beer resulted in decreased foam adhesion. These hydroxy fatty acids can be controlled by various mashing conditions. The findings presented so far indicate that the FDE value will be useful for controlling the foam behavior of beer.