| Abstract: | The optimal pitching rate in high gravity worts (12–16°P) was about 0.3 g/l wet weight (2.3 × 106 counted cells/ml) and per one percent of original wort gravity. In very high gravity worts (20–23°P) the corresponding figure was 0.4 g/l (2.9 × 106 cells/ml). Higher amounts of yeast did not improve the fermentation rate. With increased original wort gravity, flocculation of the yeast weakened and the amount of cropped yeast decreased. The viability of the crop yeast was good. In the conditions used, excessive production of acetate esters occurred only with pitching rates lower than the recommended rate. As the original wort gravity increased, more fermentable extract was metabolized to ethanol rather than utilized for yeast growth. The highest ethanol yield obtained was 10.9% (v/v). |
