Effects of organic acids on purple potato wine brewing: methanol, higher alcohols and flavor

Methanol and higher alcohols pose health risk in many alcoholic beverages. In this study, the effects of adding organic acids on the fermentation and methanol and higher alcohol levels in purple potato wine were investigated. To explore the mechanisms underlying the effects of organic acids, a transcriptome analysis and enzyme activity assays were performed. The addition of acetic, lactic, and citric acids increased the types and contents of volatile substances such as esters and acids, and improved the taste and flavor of wine. All three organic acids effectively reduced methanol and higher alcohol contents in the wine, with acetic acid exhibiting the most pronounced effect. The optimal concentration of acetic acid was 0.2%, at which methanol and higher alcohol levels were reduced by 17.72% and 31.34%, respectively. Although a higher concentration of 0.25% resulted in a slightly greater reduction, it led to excessively high total acidity, which may adversely affect wine quality.Transcriptome analyses revealed that the addition of acetic and lactic acid increased transcript levels of genes encoding alcohol acetyltransferase and alcohol acyltransferase, which are involved in ester synthesis, by 77.88% to 96.03%. Conversely, the transcript levels of genes encoding pyruvate decarboxylase and aldehyde reductase, associated with alcohol synthesis, decreased by 26.88% to 65.74%. Furthermore, the activity of pectinesterase, linked to methanol formation, decreased by 12.47% to 23.08%. This study contributes to quality improvement of potato wine and other similar fermented alcoholic drinks.