Concentration of Tartrates, Malates, Glucose and Fructose in the Fruits of the GenusVitis

Abstract

Mature fruits from 26 species of <i>Vitis</i> growing in the University vineyard at Davis were examined for total soluble solids, total acidity, pH, and concentrations of tartrates, malates, glucose, and fructose. The range of these substances in mature fruits varied widely: total soluble solids (13.7 to 31.5°B), total acidity (0.35 to 2.85 g tartaric acid/100 ml), pH (2.79 to 4.48), tartrates (0.30 to 1.19 g/100 ml), malates (0.13 to 2.72 g/100 ml), glucose (4.42 to 13.67 g/100 ml), and fructose (5.71 to 16.80 g/100 ml}. The tartrate-malate ratios ranged from 0.24 to 5.85. Nine species had tartrate-malate ratios greater than 1, and 17 species had ratios less than 1. The glucose-fructose ratios ranged from 0.47 to 1.12, with only two species containing more glucose than fructose. In addition, the concentrations of tartaric and malic acids and their salts were estimated with the Henderson-Hasselbalch equation. The tartrates and malates present as free acid respectively ranged from 2.4 to 60.5% and from 6.4 to 80.0%. Percentage of total titratable acidity due to tartrates in the fruits of the various species ranged from 14 to 80%, while that due to malates varied from 26 fo 92%. <i>Vitis labrusca, V. vinifera, V. rotundifolia</i>, and V. Spp. (from Afghanistan) were the only species in which a greater percentage of total titratable acidity was due to tartrates rather than to malates.