Evolution of aroma and phenolic compounds during ripening of 'superior seedless' grapes.

The evolution of aroma and phenolic compounds was studied during ripening of Vitis vinifera cv. 'Superior Seedless' grapes in two consecutive years. The major free detected compounds were citral, geraniol, and benzyl alcohol whereas geraniol, citral, nerol, citronellol, dienediol I, linalol oxide I, linalol oxide II, benzyl alcohol, and 2-phenylethanol were identified in the glycosidically bound fraction. Concentrations of the main free terpene alcohols responsible for 'Superior Seedless' aroma decreased during grape development, and bound compounds became predominant at grape maturity. Calculation of odor activity values showed that geraniol was the most active odorant followed to a lesser extent by citral and nerol. With regard to phenolic compound evolution, flavan-3-ols and flavonols were maximal at veraison and decreased throughout the ripening, stilbenes content decreased from the first stage, and total phenolics increased to show a maximum in the ripe grapes. At ripening, quercetin 3-O-glucoside and catechin were the main compounds detected in 'Superior Seedless'.