Changes in the Concentration of Amino Acids During the Ripening of Vitis vinifera Tempranillo Variety from the Denomination d'Origine Somontano (Spain)

¹ Department of Analytical Chemistry, Science Faculty, University of Zaragoza, Pza. San Francisco s/n, 50009 Zaragoza, Spain.

The concentration of 18 free -amino acids and total -amino acid nitrogen in musts and total nitrogen in seeds, skins, and must of the Tempranillo variety was determined from the beginning of the ripening process until harvest. Eighteen free -amino acids were also determined for Riesling, Cabernet Sauvignon, and Moristel at harvest over a period of three consecutive years in the Denomination d'Origine Somontano (Spain). Arginine, proline, histidine and glutamine were the most prominent amino acids in all four varieties. The predominant amino acid in Riesling and Cabernet Sauvignon was proline and arginine was the major amino acid in the Tempranillo variety in all the three years. In the case of the Moristel variety, arginine was the predominant amino acid one year and proline the other two. The four major amino acids accounted for 62% to 88% of the total free -amino acids. The amino acid nitrogen fraction in the juices ranged from 40% to 87% of the total Kjeldahl nitrogen. The wine with the best characteristics was obtained in the year in which total nitrogen concentration was the lowest and the total free -amino acid nitrogen concentration the highest. As the ratio of the four amino acids (proline, arginine, glutamine and histidine) to the sum total of amino acids differed significantly from one variety to another in this Denomination d'Origine, it was used as an index to differentiate between varieties from the same area. The sum total of amino acids increased during the ripening process, with individual amino acids varying from one year to another. During the ripening period titratable acidity, malic and tartaric acid decreased in Tempranillo grapes all three years while berry weight, pH, °Brix, and total nitrogen increased. There was a good correlation between arginine and the accumulation of soluble solids during the ripening process.

Key words: grape, must, amino acids, nitrogen, ripening, Tempranillo

Submitted on April 6, 1998