芝麻香型与浓香型白酒固态发酵过程中氨基甲酸乙酯的形成研究

Ethyl Carbamate Formation During Solid-state Fermentation of Sesame-flavored and Strongly Flavored Baijiu

摘要:

氨基甲酸乙酯（EC）是一种具有细胞和基因毒性的2A级致癌物质，我国部分白酒中EC检出率和含量居高不下，引起了广泛关注。本文以浓香型和芝麻香型白酒为例，探究了白酒固态发酵过程中EC、前体物质含量与酸度的变化，同时采用模拟发酵分析白酒酒醅固态发酵过程中pH值、尿素与瓜氨酸对EC形成的影响。研究表明：发酵初期的两种酒醅中均检测到超过20 μg/kg EC，发酵过程中芝麻香型酒醅中EC形成速率（4.40×10-7 μmol/kg·s）和含量（140.55 μg/kg）均显著高于浓香型酒醅，且主要积累于发酵2至4周。两种酒醅中乙醇与尿素在发酵前三周含量分别增加了679.31%~181.89%和87.54%~117.87%，发酵三周后瓜氨酸积累更多。尽管芝麻香型酒醅发酵过程中EC与瓜氨酸和尿素含量相关性均不显著，模拟实验发现添加尿素与瓜氨酸后酒醅中EC含量均增加了23.70%~84.82%，且尿素在酒醅发酵过程中形成EC的能力比瓜氨酸更强。此外，酒醅pH值低于4.0有助于发酵初期EC的形成。以上结果可为针对性降低酒醅发酵过程中积累的大量EC提供依据。

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.