Classification of grape berries according to diameter and total soluble solids to study the effect of light and temperature on methoxypyrazine, glutathione, and hydroxycinnamate evolution during ripening of Sauvignon blanc (Vitis vinifera L.)

Grape berries were classified according to diameter and total soluble solids (TSS) to study the effect of light and temperature on methoxypyrazines (MPs), glutathione (GSH), and hydroxycinnamates (HCAs) during the ripening of Sauvignon blanc. The light exposure of the fruiting zone was modified within leaf and lateral removal at the phenological stage berry of peppercorn size and no removal (control). In comparison to the control, the concentration of 3-isobutyl-2-methoxypyrazine (IBMP) was below the limit of detection in leaf removal 2 weeks before harvest. Leaf removal had no significant influence on GSH and HCAs in the grape juice at harvest. Berry diameter significantly influenced the concentration of IBMP in the grape juice and did not influence the concentration of GSH and HCAs. At harvest, the concentrations of IBMP in grape juices of similar TSS in the control were 12.6 and 5.2 ng/L in 15.5 and 13.5 mm berry diameter classes, respectively. Furthermore, the study showed that berries of the same diameter were not at the same physiological ripening level (not the same TSS).