Other Ethyl Carbamate Precursors in Juice and Wine
Post-bottling formation of ethyl carbamate in wines that have tested negative for both urea and ethyl carbamate upon leaving the winery, continues to pose a problem for the industry. This is of particular concern in the case of dessert wines. During this year’s study (1995-96), we examined the possibility that urea-carbonyl adducts formed prior to fermentation might be responsible. We had previously reported (AVF, 1994-95) that diacetyl-urea adducts did not seem to be responsible for post-bottling ethyl carbamate formation. We have since reexamined the behavior of 3a, 6a-dimethylglycoluril (one of the adducts of urea and diacetyl) and found that indeed this compound might be a precursor of ethyl carbamate in wines. We also synthesized several glucose-urea adducts (diureides and monoureides). When subjected to acid hydrolysis under conditions similar to those found in wine, these urea adducts also released urea with the production of ethyl carbamate. This behavior indicates that these compounds, that could form prior to fermentation, might also be responsible for post-bottling ethyl carbamate formation in wine.