Ethyl Carbamate Formation During Solid-state Fermentation of Sesame-flavored and Strongly Flavored Baijiu
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Abstract:
Ethyl carbamate (EC) is a Group 2A carcinogen and exerts cytotoxic and genotoxic effects. In China, high EC levels in baijiu have attracted extensive attention. In this study, the EC level, precursor content, and fluctuations in acidity during solid-state fermentation of strongly flavored and sesame-flavored baijius were investigated. In addition, the effects of pH, and urea and citrulline concentrations on EC formation during solid-state fermentation were analyzed through simulations. At the beginning of fermentation, the EC concentrations in the fermented grains of the two types of baijiu were >20 μg/kg. During fermentation, the fermented grains of the sesame-flavored baijiu displayed a significantly higher EC formation rate (4.40×10-7μmol/kg·s) and a considerably higher EC content (140.55 μg/kg) than the grains of strongly flavored baijiu. EC accumulated in the fermented grains of the sesame-flavored baijiu during the second to fourth weeks of fermentation. During the first three weeks of fermentation, the ethanol and urea contents of the fermented grains in sesame flavored and strong flavored baijiu rose by 679.31%~181.89% and 87.54%~117.87%, respectively. Cumulative citrulline concentrations were higher after three weeks of fermentation. Although EC concentrations exhibited no significant correlations with citrulline or urea concentrations during grain fermentation in sesame-flavored baijiu, simulation revealed that addition of urea and citrulline increased EC content by 23.70-84.82%. Furthermore, urea promoted EC formation more vigorously than citrulline. Lastly, a pH lower than 4.0 promoted EC formation during early stage fermentation. These findings provide new strategies to reduce the EC accumulation in baijiu during fermentation.
