摘要：Urethane, ethylcarbamate, which is known to be carcinogenic, teratogenic and mutagenic, was reported to be contaminated in various kinds of alcoholic beverages. Therefore, removal of urethane or prevention of its formation from alcoholic beverages is an urgent problem in all over the world. The present review describes, 1. toxicity of urethane, 2. methods of its measurement, 3. mechanism of its formation and 4. prevention of its formation. Urethane was chemically produced from carbamyl compounds and ethyl alcohol by heating in an acidic condition of fermentation. For example, urethane (20-60 ppb) in sake and wine was produced from urea as a major carbamyl source during sterilization process or long-term storage. Urethane contamination levels were dependent upon acidicity, temperature, periods of time and the concentrations of urea and of ethyl alcohol. Acid urease, whose optimal pH lies around 4, obtained from Lactobacillus reuterii lowered urea concentrations in sake and wine, whose pHs are acidic (pH 4.4 and 3.2, respectively). On the basis of these results, enzymatic removal of urea with acid urease during or after fermentation processes and before heating or storage prevented the urethane formation in sake and probably in other alcoholic beverages. Urethanase which hydrolyzes urethane in the acidic region in high ethyl alcohol concentrations is expected to be useful for the elimination of a potentially hazardous compound once formed in distilled alcoholic beverages.
