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.)

Abstract

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).

Impact of agronomic practices on grape aroma composition: a review

“…Most of them have focused their research on the main aroma molecules: glycosylated aroma precursors, free aroma volatiles, C 13 ‐norisoprenoids, terpenes, and methoxypyrazines. Although the removal of basal leaves around a bunch is usually chosen to increase the exposure to light, some authors have used artificial shading (e.g., boxes) …”

Antioxidants in Wine during Fermentation

“…γ-Glutamylcysteine synthetase produces γ-glutamylcysteine from L-glutamate and L-cysteine. Certain authors reported GSH concentrations in ripening grapes to increase up to about 16 degree Brix (Okuda and Yokotsuka, 1999), while others found levels to increase up to commercial harvest at around 25 degree Brix (Suklje et al, 2012). GSH can occur in white grapes at a few milligrams to more than 100 mg/kg (Kritzinger et al, 2013a), depending on the cultivar and ripening stage.…”

“…However, their concentration decreases, especially in the skin, due to berry growth. HCA are synthesized in the early stages of berry formation, while levels decrease in the early stages of ripening, but then seem to stabilize at the later stages of ripening (Suklje et al, 2012). Flavonols have two distinct phases of synthesis: the first around flowering with the other during ripening of the grape berry (Downey et al 2003).…”

Sensory interaction between 3-mercaptohexan-1-ol and 2-isobutyl-3-methoxypyrazine in dearomatised Sauvignon Blanc wine

“…Winemakers could thus harvest grapes at a lower grape sugar level to obtain a higher concentration of methoxypyrazines if greener notes are preferred or at a later stage if more tropical-associated aroma attributes are required in the wines (Pineau et al 2011). Factors such as growing Sauvignon Blanc grapes in cooler climates Swart 1999, Marais et al 1999) and less light exposure during ripening (Suklje et al 2012) can also increase IBMP concentration in Sauvignon Blanc wines and thus in greenassociated sensory attributes, such as green pepper and overall green. Skin contact before fermentation, which can further increase IBMP concentration (Maggu et al 2007), should also be considered if even a higher concentration is required with a potential increase in asparagus and green grass attributes.…”