Management And Use Of Yeast In High Gravity Brewing Process

In the conditions of high gravity brewing, the yeast faced some problems, such as thewort with higher sugar and bigger viscosity and wort osmotic pressure at the beginning of thefermentation, and the elevated ethanol concentrations and the lacked nutrients towards theend of the fermentation. All those factors would reduce yeast fermentation performance andbeer quality. Therefore, yeast should be managed and used correctly in high gravity brewing.In this paper, the effect of recycling yeast washing, adding exogenous sugar, andchanging osmotic pressure on yeast high gravity brewing was studied preliminary. The mainexperiment results are as follow:1. The osmotic pressure and nutrition environment of washing yeast affect the yeastfermentation performance. The fermentation performance of recycled yeast after beingwashed with wort was improved by washing the yeast with wort,12°P wort was chosen forwashing recycled yeast.2. In high gravity brewing, the number of yeast cells, the concentration of ethanol,trehalose and flavor compounds could be increased, but the reducing sugar, amino nitrogenutilization and apparent fermentation degree was significantly decreased. Increasing thegravity by adding the maltose would result in improving yeast performance and flavor profile,so the wort containing higher maltose should be used in high gravity brewing.3. Yeast could utilize glucose and maltose, but couldn’t use trehalose. However, a certainconcentration of trehalose would accelerate fermentation, enhance the metabolism viability ofyeast, and improve the tolerance of yeast in high gravity brewing.4. Increasing the environment osmotic pressure would put off the cell growth anddecrease sugar utilization, ethanol production and viability rate of cells, furthermore, reducethe apparent fermentation degree, and increased the concentration of intracellular trehaloseand alcohol to ester ratio. It was indicated that high osmotic pressure was harmful to beerbrewing by yeast.