THE LOSSES OF BITTER SUBSTANCES DURING FERMENTATION

Almost all of the bitter substances which are lost during pilot-scale brewery fermentations using yeast N.C.Y.C. 240 can be recovered unchanged. The largest losses of bitter substances are associated with the dirty head formed during the first 18 hours of a fermentation. Hop utilization can be improved by folding this dirty head back into the fermenting wort. This process is most effective when carried out after the ethanol concentration of the wort has reached about 1%, but before the bitter substances have had the opportunity to undergo extensive oxidative degradation. Losses of bitter substances are lower when 25% of a malt grist is replaced by wheat flour. There is no consistent relationship between losses of bitter substances and either the assimilable or total nitrogen of wort. With increase in wort O.G. there is increasing loss of bitter substances, such losses being principally associated with the dirty head.