TY - JOUR T1 - Formation of Ethyl Carbamate Precursors During Grape Juice (Chardonnay) Fermentation. I. Addition of Amino Acids, Urea, and Ammonia: Effects of Fortification on Intracellular and Extracellular Precursors JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 243 LP - 249 DO - 10.5344/ajev.1988.39.3.243 VL - 39 IS - 3 AU - C. S. Ough AU - E. A. Crowell AU - L. A. Mooney Y1 - 1988/01/01 UR - http://www.ajevonline.org/content/39/3/243.abstract N2 - Investigations into the possible precursors for ethyl carbamate with a Chardonnay juice with various additions and treatments indicate significant amounts of precursor can be accounted for by the breakdown of the arginine to form ornithine and urea. This is further substantiated by increases in ornithine, glutamic acid + asparagine, and proline. While it is recognized that citrulline and carbamyl phosphate are also possible reactants, these seemed not to be a significant consideration in these particular experiments. Approximately 40% to 50% of ethyl carbamate precursors could be accounted for by "estimates" of urea at the end of fermentation. In addition to the presence of arginine, it seems that an imbalance in the amino acids and ammonia composition of the juice is required for increased ethyl carbamate precursor formation. The fortification of juice during fermentation changes the amount of ethyl carbamate precursors. Alcohol additions cause a greater percent conversion in the early to middle stages of fermentation when fortification occurs in the presence of yeast than when the yeast is removed. At the latter stages, much less difference occurs. Saccharomyces bayanus (California champagne) produced significantly less ethyl carbamate precursors than did S. cerevisiae (Montrachet) in these experiments. ER -