Ethyl Carbamate Formation: Reaction of Urea and Citrulline with Ethanol in Wine Under Low to Normal Temperature Conditions

¹ Department of Viticulture and Enology, University of California, Davis, CA 95616-8749.

A two year storage study determined the effect of time and temperature on the formation of ethyl carbamate from the reaction of ethanol with urea and with citrulline. Under fairly normal storage temperatures (13.1°C to 23.9°C) and not uncommon concentrations of urea (1 to 10 mg/L), a significant amount of ethyl carbamate will accumulate over a two-year period. The formation rates of ethyl carbamate due to urea concentration only, for a table wine of about 12% ethanol, were per mg urea per day 0.0004, 0.0017, and 0.0061 µg ethyl carbamate at 13.3°C, 18.6°C, and 23.9°C, respectively. Other factors, such as pH and wine type, are not as significant to the accumulation. From this data we were able to verify that some other compounds(s), other than urea and citrulline, are contributing to the formation of ethyl carbamate. Best estimates of potential ethyl carbamate that may be formed should include consideration of temperature of storage and effects on rate of formation by urea, citrulline, and other contributing factors.

Key words: ethyl carbamate, urea, citrulline, wine storage

Submitted on August 18, 1992

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