Effects of Flower Cluster Tip Removal on Phenolics and Antioxidant Activity of Grape Berries and Wines

Insufficient sunlight during veraison to maturity of winegrapes is a primary factor that inhibits production of phenolic compounds. In this study, a novel thinning technique called cluster tip removal (CTR) was applied to inflorescences of Vitis vinifera L. Marselan grapes, and the berry composition, phenolic profiles, and antioxidant activities of berry skins and wines were determined. CTR of inflorescences reduced cluster compactness, lowered titratable acidity, and increased total soluble solids in berries. CTR also increased concentrations of total phenolics, anthocyanins, tannins, and flavonoids in the pedicel end of berry skins and enhanced concentrations of 12 phenolic compounds. It also increased the concentrations of total flavanols and anthocyanins in wines. CTR berries and wines also had increased antioxidant capacities. Finally, expression of phenolic-related genes was upregulated in the skin of CTR berries.