Assimilable nitrogen reduces the higher alcohols content of huangjiu

Yeast assimilable nitrogen (YAN) sources play an important role in the formation of higher alcohols in wine. In this study, the types and amounts of YAN sources and the genes that regulate the synthesis of higher alcohols in a yeast used for huangjiu brewing, Saccharomyces cerevisiae HJ, were assessed for the first time. Quantitative realtime PCR experiments demonstrated that S. cerevisiae HJ genes controlling the production of higher alcohols were expressed at significantly different levels during different growth stages and at different YAN levels, indicating that YAN significantly impacts the total higher alcohols concentration of huangjiu. Ammonium salts especially NH4Cl showed greater effect in reducing the content of higher alcohols than amino acids or urea. After optimization, the addition of NH4Cl (200 mg/L) most effectively reduced the content of higher alcohols at the end of fermentation with little effect on the cell growth rate, final cell density and ethanol concentration. Total higher alcohols decreased by 39%, while the concentrations of isobutanol, isoamylol and 2-phenylethanol decreased by 47%, 28%, and 44%, respectively. The addition of NH4Cl promoted the formation of esters and enriched the amino acids in huangjiu. This study provides a new insight to control the quality of huangjiu, especially the content of higher alcohols based on the strategy of adding NH4Cl.

Automated summary

This study assessed the types and amounts of YAN sources and genes regulating higher alcohol synthesis in a yeast used for huangjiu brewing. It found that NH4Cl was most effective in reducing higher alcohol content, providing insights for controlling huangjiu quality by adding NH4Cl.