Quantitative comparison of free and bound volatiles of two commercial tomato cultivars (Solanum lycopersicum L.) during ripening.

The changes in the profile of both free and glycosidically bound volatiles were studied in Moneymaker and Raf tomato cultivars during fruit ripening. The concentrations of 20 of 24 and of 27 of 30 compounds detected in the free volatile fraction (FVF) and glycosidically bound fraction (GBF), respectively, differed significantly between cultivars during ripening. Most free and bound volatiles increased during ripening in both cultivars. The contribution of each free volatile compound to the overall aroma was estimated by calculating its log U value, which indicated that only 11 compounds seem to exert a strong influence. Nine volatiles were detected exclusively in the GBF, among them geraniol, beta-citronellol, alpha-terpineol, and trans- and cis-linalool oxides. Nine other compounds were found to be more abundant in the GBF than in the FVF, their absolute levels varying between cultivars and stages of ripening. According to the log U values reached, of these nine compounds, linalool, 3-methyl-1-butanol, trans-2-hexenal, eugenol, and 2-phenylethanol may have an impact on tomato aroma upon release from their glycosidic conjugates. Sugars resulting from the enzymatic hydrolysis of the GBF were detected by high-performance liquid chromatography. Rhamnose was the most abundant followed by arabinose, glucose, and xylose.