Flavor composition has been defined as a complex attribute of fruit quality, in which the mix of sugars, acids and volatiles
play a primary role. In table grapes (
Vitis vinifera
L.), sweetness and sourness are the most important flavor attributes for
fresh consumption. However, most of the studies available have been performed on wine grapes, which are grown, cultured
and processed differently to table grapes. Therefore, the objective of this work was to characterize the changes in sugars and
organic acids during the development of 'Thompson Seedless', 'Red Globe' and 'Crimson Seedless' grown under the same
agroclimatic conditions. Each variety was sampled weekly from 2 wk before véraison until commercial harvest. Sugars
and organic acids were quantified by high performance liquid chromatography (HPLC) equipped with an evaporative light
scattering detector (ELSD) and ultra violet detector, respectively. The ranges of acid and sugars concentrations found in
grapes were as follows: tartaric acid, 1.28-7.45 g L
-1; malic acid, 0.38-29.92 g L
-1, citric acid traces-1.03 g L
-1; fructose, 0.15-8.74 g (sugar) 100 g(grape)
-1; glucose, 0.19-8.71 g (sugar) 100 g(grape)
-1 and sucrose 0.02-0.91 g (sugar) 100 g(grape)
-1.
Among sugars, glucose was the most abundant one in early stages and then it decreased until the harvest period, when
the amount of fructose and glucose converged to an average of 47% for each sugar. Despite organic acids reaching steady
levels 3-4 wk before commercial harvest, there were important differences in the organic acid profiles among varieties,
with 'Thompson Seedless' showing the lowest tartaric/malic acid ratio of 1.19. These differences are an important aspect
in terms of overall flavor.
