HOP SUBSTANCES AND YEAST BEHAVIOUR

Abstract

Top fermentation yeast strains vary in their ability to form a yeast head in the absence of hop substances. However, the addition of isohumulone or humulone to unhopped wort stimulates yeast‐head formation. A quantitative method for the estimation of hop substances bound to the yeast cell is described and is used to demonstrate that in top fermentation, most of the adsorbed bitter substances are present in the head. It is shown that most of the hop substances in the yeast head are transported there by bubbles of carbon dioxide; in bottom fermentation, considerable quantities are present in the surface foam. In comparison with hopped wort the fermentation of unhopped wort with Saccharomyces cerevisiae (N.C.Y.C. 240) is characterized by an increased amount of yeast in suspension during fermentation, although there is no increase in the rate of attenuation. 1967 The Institute of Brewing & Distilling