Free Amino Acid Composition of Grape Juice From 12 Vitis vinifera Cultivars in Washington

Abstract

Free amino acid concentrations in juice of 12 Vitis vinifera cultivars grown in the Columbia and Yakima Valley appellations of Washington state were monitored from 1986 to 1990 for a total of 728 samples. When averaged across all years, arginine (expressed as mg/L) was the predominant amino acid in Gewürztraminer, Muscat Canelli, Semillon, and Pinot noir juices. Proline was predominant in juices of Chenin blanc, Chardonnay, Cabernet Sauvignon, Grenache, Lemberger, Merlot, Sauvignon blanc, and White Riesling. However, arginine concentration varied widely between years. Arginine, proline, proline:arginine ratio, total free α-amino acid and total free α-amino N concentrations were not correlated with soluble solids concentration at harvest. Washington juices tended to be lower in amino acid concentration than those reported for the same cultivars in California. More than 60% of the juice samples of each cultivar contained less than 400 mg total free α-amino N/L. This percentage was over 80% for all but Gewürztraminer and Muscat Canelli. All of the Cabernet Sauvignon, Lemberger, and Merlot juice samples contained less than 400 mg total free α-amino N/ L. Additionally, 93% of the Cabernet Sauvignon and 88% of the Merlot juices contained less than 200 mg total free α-amino N/L. Of the white-fruited cultivars, White Riesling (96%), Chenin blanc (94%), and Sauvignon blanc (92%) juices had the highest percentage of samples under 400 mg total free α-amino N/L. Seventy-seven percent of the White Riesling juices contained less than 200 mg total free α-amino N/L. Across all samples, 39% contained less than 150 mg total free α-amino N/L of juice, 58% contained less than 200 mg total free α-amino N/L of juice, and 90% contained less than 400 mg free α-amino N/L of juice.