Varietal and pre-fermentative volatiles during ripening of Vitis vinifera cv Nebbiolo berries from three growing areas

Abstract

27Flavour analysis of grape is a key step in quality evaluation. The Stir Bar Sorptive Extraction 31(North-western Italy). Volatile constituents of grapes were identified and quantified by GC-MS. 32We demonstrate the influence exerted by the growing location on volatile concentration and 33 profile, as well as on the timing of volatile accumulation. The accumulation of certain classes of 34 compounds, considered favourable for defining berry quality, followed common patterns, and 35 was negatively correlated to that of compounds with herbaceous and grassy notes, such as the C6 36compounds. 37PCA analysis shows that the concentrations of varietal and pre-fermentative volatiles were more 38 effective in separating growing areas than dates of harvest. Grapes from the Barbaresco area, 39showing higher values of the concentration ratio between favourable and unfavourable 40 compounds throughout ripening, could be statistically separated from grapes from the other areas.

Aroma characterization of grape juice enriched with grapevine by-products using thermomaceration

“…These compounds could be divided in nine chemical classes with their characteristic aroma descriptors: Terpenoids (two compounds), norisoprenoids (three compounds), lactones (two compounds), aldehydes and ketones (six compounds), alcohols (six compounds), benzenoids (nine compounds), alkenes (one compound), acids (eight compounds) and esters (13 compounds). The identified components have been reported before in grape and grape-derived products (Weldegergis et al, 2011;Ferrandino et al, 2012;Galano et al, 2015;Ghaste et al, 2015;González-Barreiro et al, 2015;Vararu et al, 2015;Yuan and Qian, 2016;Wang et al, 2017).…”

Application of a stir bar sorptive extraction method for the determination of volatile compounds in different grape varieties

“…Therefore, the stirring speed was set at 750 rpm. This value is in agreement with those employed in previous studies, where 700 rpm was used …”

“…From this study, NaCl percent was fixed at its highest value (25%, limited by solubility). Although ionic strength is a variable commonly studied in SBSE, it had not been previously evaluated in the literature when SBSE was applied to grapes . By increasing ionic strength, the relative solubility of volatile compounds in the polar aqueous medium decreases and increases the relative solubility in a non‐polar medium such as PDMS.…”

“…Considering its positive effect and its commercial availability, the 20 mm × 0.5 mm (length × film thickness) stir bar was selected. Other authors employed 10 mm stir bars instead of 20 mm stir bars, but the length of the stir bar was not studied in the works mentioned. Stirring speed did not affect the response ( P = 0.1317), but an irregular stirring was observed at high velocity when a high concentration of NaCl was used.…”

“…SBSE was also employed for the determination of volatile organic constituents in synthetic grape juice . To date, just a few applications use this technique for detecting volatiles directly in grape extract, but optimization of the best analytical conditions and study of the performance characteristics of the SBSE methodology seem under‐studied in all cases.…”