An Additional Explanation for the Promotion of More Rapid, Complete Fermentation by Yeast Hulls

¹ Food Biotechnology Group, Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Sask. S7N 0W0, Canada.

Fermentations were carried out using three different yeast hull preparations at 1 g/L concentration in a nitrogen-deficient Chardonnay must under limited oxygen supply. The yeast hulls enhanced fermentation rate and stimulated the growth of more yeast cells and cell mass when compared with unsupplemented controls. Ergosterol and Tween 80 (a source of oleic acid) supplements in musts had the same enhancing effects as the hulls. Yeast hulls were analyzed for their usable nitrogen, total sterol, and fatty acid contents. Their actions as fermentation promoters are postulated to be due to their role as providers of oxygen substitutes (sterols and unsaturated fatty acids), as well as through the previously reported adsorption of medium chain length fatty acids.

Key words: yeast hulls, ghosts, survival factors, stuck fermentation, sterol

Submitted on May 4, 1988