Nitrogenous Constituents of Brewing Materials: V. Examination of the Action of Selected Precipitants on Brewers' Worts

Abstract

The system of wort analysis evolved by Lundin, using tannic acid for the precipitation of proteins and phosphomolybdic acid for the precipitation of proteins and peptides, yielded reproducible results, which were closely comparable with those obtained by Myrbäck's procedure using magnesium sulphate for proteins and uranyl acetate for proteins and polypeptides. The material precipitated from wort by tannic acid or magnesium sulphate precipitates the bulk of the undialysable compounds of wort, and these reagents therefore show some specificity for complex nitrogenous compounds. On the other hand, colloidal iron sometimes precipitates dialysable nitrogenous material together with the undialysable compounds and is therefore regarded as less specific. Using Lundin's method, more nitrogenous material was found in a wort prepared by mashing malt at 150° F. for 4 hr. than when employing the same temperature for only 1 hr.; in the former case a greater proportion consisted of relatively simple compounds. Again, the amounts of all nitrogenous fractions of the worts diminished during fermentation, but the decrease in the simpler compounds greatly overshadowed that of the more complex materials. Of the compounds assimilated, a considerable proportion consisted of materials other than amino acids.