Using fed-batch fermentation in very high gravity brewing: effects of Tween 80 and ergosterol supplementation on fermentation performance of immobilized yeast in calcium alginate gel

In very high gravity brewing, fed-batch fermentation was carried out with Saccharomyces cerevisiae immobilized in calcium alginate gel. The specific gravity of initial wort and feeding medium originated from 55% malt and 45% maltose syrup adjunct was adjusted to 28 o Brix and 41 o Bx, respectively. The effect of supplementation of mixture of Tween 80 and ergosterol to the initial wort or to the feeding medium was examined. The results indicated that addition of 0.3% (v/v) Tween 80 and 24ppm ergosterol to the initial wort improved the fermentation performance of the immobilized yeast. Under these conditions, the primary fermentation time reduced 24h and the ethanol concentration was similar in comparison with those of the fed- batch culture without the supplementation.