Yang He (1); (1) Tsingtao Brewing Ltd., Qingdao, China
Yeast, Fermentation, and Microbiology
Brewery wort is a complex yeast growth and fermentation medium that contains an array of assimilable nitrogen. Among all the assimilable nitrogen, amino acids are the most abundant. Alterations related to nutritional parameters (e.g., malt varieties, novel adjuncts, adjunct composition, adjunct ratios or even mashing regimes, etc.) can lead to changes in the concentration of specific amino acids in wort. Amino acids composition and their utilization by yeast during wort fermentation influence both yeast fermentation performance and the flavor profile of the finished product, which, therefore, is critical for maintaining product quality and consistency. This is particularly the case with multisite brewing. Here, using an industrial lager brewing strain of Saccharomyces pastorianus, we investigated the effect of amino acids composition on yeast fermentation performance and beer flavor. A two-level factorial Plackett-Burman design was applied to screening the most significant amino acids in brewing wort. Based on the results, glutamine and proline were found to be negatively affected by yeast propagation and yeast amino acid utilization. Lysine was identified as a important determinant for promoting yeast propagation. Furthermore, the maturity of beer was positively exercised by the amount of valine in wort. The statistical design tool greatly facilitates the understanding of the importance of each amino acid and the desired ones in wort. The future applications of this information could drastically improve current regimes for selecting malt and adjunct or their formula.
Yang He is a scientist at State Key Laboratory of Biological Fermentation Engineering of Beer, Tsingtao Brewing Ltd. Most of her research is related to beer flavor production during fermentation by monitoring yeast gene expression. She received her Ph.D. degree in marine science from the Ocean University of China in 2011.