Insights into the mechanism of oaky flavor enhancement by Brettanomyces bruxellensis 23 during beer fermentation.

Abstract

To accelerate the development of oaky flavor in beer and reduce barrel-aging costs, Brettanomyces bruxellensis 23 with high β-glucosidase-producing ability was screened via four-round screening. This strain exhibited robust tolerance to 0-10% ethanol, 0-70 IBU, 0-15 g/L oak chips and 0-20oP wort gravity. Mechanistic studies revealed that B. bruxellensis 23 primarily converted environmental precursors into flavor compounds instead of de novo synthesis. Further investigation revealed that its flavor producing ability relied on synergistic effect of cells and secreted enzymes, among which yeast cells primarily promoted terpenes formation while extracellular enzymes contributed to the formation of lactones and aldehydes. When applied in lab-scale fermentation with oak chips, B. bruxellensis 23 produced beer with significantly intensified and more harmonious oaky characters compared to commercial Saccharomyces cerevisiae 256 while maintaining standard physicochemical parameters. This study positioned B. bruxellensis 23 as a promising functional culture for efficiently producing oak-aged beer with reduced production costs.

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