Free Amino Acids and Other Nitrogenous Substances of Table Grape Varieties

SUMMARY — The concentration of eight amino acids, total free amino acids, total nitrogen and free amino acid fraction nitrogen in the juices of 28 table varieties of grapes was determined at both early and a late stage of fruit maturity. Arginine, proline, glutamic acid and alanine were the most prominent amino acids. The varieties were classified into four groups according to which of these acids predominated. Total free amino acids at early and late fruit maturity ranged from 1.04 to 5.53 and 1.24 to 6.45 nM/100 ml juice, respectively in the various varieties. The eight amino acids analyzed accounted for 74 to 96% of the total free amino acids. The amino acid fraction nitrogen in the juices ranged from 60 to 90% of the total nitrogen. The eight amino acids accounted for 60 to 96% of the amino acid fraction Kjeldahl nitrogen and 37 to 85% of the total Kjeldahl nitrogen. Argining accounted for 15 to 50% of the total nitrogen in the juices of the various fruits.