Other Ethyl Carbamate Precursors in Grape Juice and Wine
The study shows the results of duplicate experiments where the production of ethyl carbamate upon accelerated storage respectively on a white, and a red wine control were compared with the same wine to which urea, the glucose ureide, and the glucose monoureide were individually added at 2 ppm. The results for both types of wine show that, as expected, the glucose diureide does release some of its urea increasing the ethyl carbamate content upon accelerated storage. Thus, this compound could be a source of post-bottling ethyl carbamate in wines. It was surprising however, that the monoureide did not similarly release urea, indicating that, contrary to what was expected, the monoureide is not a precursor of ethyl carbamate in wine. Apparently in the latter compound, urea is tenaciously held by glucose even in the acidic conditions of the wine. Our results also indicate that under prolonged urease contact, no additional ethyl carbamate was produced from the diureide. We believe this was due to the diureide reaching an equilibrium between it and the glucose plus urea, thereby allowing the urease to destroy the freed urea. As urea is destroyed, the equilibrium eventually shifts, resulting in the complete destruction of the diureide. At this time, it is not known whether the diureide is susceptible to destruction by the urease directly. From the results obtained herewith, it is obvious that the sugar ureides are not a serious source of post-bottling ethyl carbamate in wines when these wines are properly treated with urease. Thus, work on these compounds as potential sources of ethyl carbamate in wines is hereby discontinued.