Preventing and reducing ethyl carbamate in wine
Andrew L. Waterhouse
Viticulture and Enology,University of California,Davis,California
Abstract：Ethyl carbamate is a natural constituent of wine and other fermented products, but levels are higher in products containing substantial levels of ethanol.EC has been found to have mutagenic potential, and thus levels are regulated in some markets.It is formed largely by the reaction of ethanol with urea as well as citrulline.The levels of urea and citrulline in a finished wine depends on the concentration of available nitrogen during fermentation, so that a nitrogen rich must will result in higher levels of urea and citrulline. Methods for managing EC are several, and new methods are appearing. While fermentations require nitrogen, limiting excess nitrogen sources during fermentation will reduce urea and citrulline in the wine, so vineyard fertilization and fermentation supplement practices are the first line of defense.Yeast have differing abilities to produce urea and citrulline, so yeast selection is important, especially when musts are high in nitrogen. Modified yeast are under testing and development but have potential problems to overcome. It is also possible to metabolize urea to carbon dioxide and ammonia with urease enzyme, but citrulline is not degraded and can still react with ethanol to make EC.Once EC is formed, the enzyme urethanase could potentially degrade EC, but the commercial application of this system needs development. While prevention via low to moderate nitrogen fermentation inputs are the most important factor in EC management, new techniques are beginning to provide remediation approaches as well.