Factors that influence the ethanol tolerance of brewer's yeast strains during high gravity wort fermentations.

Stewart, G.G., D'Amore, T., Panchal, C.J. and Russell, I.

Abstract
The overall rate of wort fermentation is influenced by osmotic pressure, ethanol concentration of the medium and osmotic pressure and sugar tolerance of the yeast strain employed. During early stages of fermentation intracellular accumulation of ethanol is observed in synthetic media and wort. An assimilation of intracellular and extracellular ethanol occurs during progressing fermentation. Increasing osmotic pressure is associated with increased intracellular accumulation of ethanol. Nutrient limitation is considered responsible for decreases in growth and fermentation activity of yeast at higher osmotic pressures. Supplementation with peptone yeast extract, magnesium and potassium salts has a positive effect upon the overall fermentation rate.
Keywords : brewers' yeast cell ethanol fermentation high gravity brewing medium osmosis pressure wort