Kinetic Analysis of Ester Formation During Beer Fermentation

Abstract

Most of the ester compounds found in beer are produced by yeast during fermentation. They contribute significantly to beer flavor. Therefore, the control of their formation is very important to maintain consistent quality or develop new products with unique characteristics. In this work, the influences of fermentation temperature, trub content in wort, dissolved oxygen content, and dissolved CO2 concentration on the production of ethyl acetate and isoamyl acetate were analyzed by kinetic methods. The results demonstrate that the production of ethyl acetate is little influenced by the growth of the yeast cells but can be quantitatively expressed as a function of ethanol formation. In contrast, the production of isoamyl acetate is influenced by the growth of the yeast cells, but its production per yeast cell is similarly expressed as a function of ethanol formation. It was also found that the rate constant of the production of ethyl acetate and isoamyl acetate showed a large variation between the logarithmic and stationary phases of yeast growth, and that fermentation conditions significantly influenced the rate constant of production.