Significant amino acids in aroma compound profiling during yeast fermentation analyzed by PLS regression

The biochemical formation of aroma-active metabolites determines different characteristics of aroma and taste in fermented beverages. Amino acid utilization by yeast during brewer's wort fermentation is seen as linked to flavor profile. For major understanding of the relationship between amino acid composition in wort and their impact on the synthesis of aroma-active metabolites amino acids were varied in synthetic medium and fermented by Saccharomyces cerevisiae strain S81 and Saccharomyces pastorianus var. carlsbergensis strain S23, respectively. After fermentation of different amino acid combinations higher alcohols and esters were detected by gas chromatography to determine specific aroma compound spectrum. Partial least square (PLS) regression and variable importance in the projection (VIP) were used to establish a relation between amino acids and the resulting concentrations of aroma compounds by means of pattern recognition, indicating most representative amino acids in aroma compound synthesis during fermentation. Thus, a fingerprint of amino acid importance on the detected aroma compound spectrum was created. The most important explanatory variables affecting the synthesis of aroma-active substances of S. pastorianus var. carlsbergensis are leucine, isoleucine, valine, glutamine, cysteine and surprisingly proline. In case of S. cerevisiae the significant amino acids are leucine, isoleucine, valine, histidine, glutamine and again proline.