Some nitrogenous constituents of wort and their fate during fermentation by top and bottom fermentation yeasts

Abstract

A quantitative examination of the more important nitrogenous groupings present in wort, e.g., ammonia N, amino acid N, asparagine N, residual N and protein N have been made, and their fate in fermentation by top and bottom-yeasts followed. The presence of 18 individual free amino acids has been detected in wort and the behaviour of 16 during fermentation by top and bottom-yeasts followed by microbiological assay. Seven “essential” amino acids in yeast protein have been determined. The yeast was grown on media containing different sources of nitrogen. With the exception of methionine, all the acids were constant in amount whatever the nature of the medium. The concentration of methionine in yeast protein could be increased by increasing its concentration in the medium.