Investigations into Ethyl Carbamate, n-Propyl Carbamate, and Urea in Fortified Wines

Abstract

A number of fortified wines, old and young, were analyzed for ethyl carbamate, n-propyl carbamate and urea. The pattern for port-type wines was found to be fairly low in both urea and ethyl carbamate, although several new U.S. ports were high in urea. The old U.S. sherry wines had the highest average ethyl carbamate and urea, but these averages were influenced strongly by two high values out of the 15 tested. Old Spanish, new Spanish and new U.S. sherries had low values. Vermouths had the lowest values. The effect of yeast strain and arginine on the urea concentration left in the wine after fortification was demonstrated. Model wine solutions were used to determine the relative rates of carbamate formation of ethyl and n-propyl alcohols with urea. The ethanol reacts about 1.34 times as fast as does the propanol (on a molar basis). Arrhenius plot allowed the determination of the probable amounts of n-propyl carbamate that might form in wines. Those new and old fortified wines that were analyzed for n-propyl carbamate, and nothing over 1 µg/L was found. No sample, even after heating, could be determined to positively contain n-propyl carbamate.