Ethyl Carbamate Formation in Wine: Use of Radioactively Labeled Precursors to Demonstrate the Involvement of Urea

Abstract

The formation of ethyl carbamate was investigated in model solutions and in wines using radioactively labeled urea and monitoring the appearance of that radioactivity in ethyl carbamate. There was a striking temperature dependence for the rate of the reaction as well as a dependence upon urea and ethanol concentrations. The source of urea during fermentation was investigated using radioactively labeled arginine (<i>guanido</i>-¹⁴C). Under the conditions used here, arginine was degraded to urea, and some urea was released into the fermentation medium. More urea could be released from the cells when ethanol concentration was elevated, as a consequnce of fortification of the must. There was significant turnover and degradation of arginine in cells incubated in the presence of ethanol, as would occur during commercial fortification of musts. Thus, urea can be formed during vinification and, if released into the medium, will yield ethyl carbamate through reaction with ethanol.