Development of a Spectrophotometry Assay for Arginine, a Precursor to Ethyl

Ethyl carbamate is a natural fermentation byproduct but a potential carcinogen at very high doses. The major precursor to ethyl carbamate in wine is arginine, a natural amino acid in grapes. In order to minimize ethyl carbamate levels in wine, we developed a simple, rapid method for determining the arginine concentration in grape juice, that is suitable for use at a commercial winery. The new spectrophotometry assay for arginine utilizes techniques adapted from ion exchange chromatography. In our method development, we combined the application of a selective strong cation exchange resin with the NOPA assay that we developed in the previous AVF project “Rapid Analysis for Yeast Available Nitrogen Compounds in Must”. We have been able to demonstrate the isolation and quantification of arginine from various model and natural juices. The accuracy and reliability of our assay was evaluated by correlation to a HPLC reference method, and by measuring the recovery of arginine in spiked model and natural juices. The assay will be tested on commercial musts during the 1998 crush, and an analytical procedure will be made available to the California wine industry as soon as our method validation is complete. Recommendations on critical arginine levels in juices have already been made in our “Ethyl Carbamate Preventative Action Manual”.