Comparison in changes in sugars, organic acids and amino acids during berry ripening of sucrose- and hexose-accumulating grape cultivars

Abstract

Sucrose- and hexose-accumulating grape cultivars were studied by monitoring changes in °Brix, total and individual sugars, free and total acidity, individual organic acids, total and individual amino acids during ripening. °Brix and total sugar content increased continuously and steadily after veraison until maturity. °Brix was significantly higher in the sucrose accumulators than in the hexose accumulators. The glucose level decreased with the berry ripeness, while that of fructose increased correspondingly. The sucrose content of the sucrose accumulators was much higher than that of the hexose accumulators. Free acidity decreased rapidly and continuously after veraison. The ratio of free acidity to total acidity (F/T ratio) decreased gradually, reaching a final level of about 0.5. A ratio of tartaric acid to malic acid (β ratio) rose steadily, and changed significantly near maturity. Total amino acid content which increased continuously after veraison consisted of primarily threonine (Thr), glutamic acid (Glu), alanine (Ala), and arginine (Arg). While Thr and Arg levels gradually decreased, a corresponding increase in Glu and Ala occurred. No significant change took place in the sugar composition (α ratio) and amino acid composition (γ ratio) near maturity.