Impact of Leaf Removal on Phenolics and Antioxidant Activity of Trebbiano Berries (Vitis vinifera L.)

Leaf removal is a canopy management practice widely applied in viticulture to enhancethe phenol composition and concentration of grapes, which then results in improved wine quality.Many studies were carried out on red berried varieties, but information on white ones is scanty.The aim of the study was to assess the effect of basal leaf defoliation in post fruit set on the phenolcomposition, ascorbate level and antioxidant activity of Trebbiano grapes. Electron paramagneticresonance was also employed to monitor the decay kinetics of 1,1-diphenyl-2-picrylhydrazyl whichallowed the identification of antioxidants with different action rates. The results show that defoliationcaused an increase in the phenolic acid (hydroxycinnamic and hydroxybenzoic acids) and flavonolconcentrations of berries without changes in the composition. Both ascorbate and antioxidant activitywere also enhanced in the berries from defoliated vines. Besides increasing the number of fast-rateantioxidants, leaf removal resulted in the formation of intermediate-rate ones. In the Trebbianovariety, leaf removal in the post fruit set may represent an effective strategy to enhance the phenoliccomposition and the antioxidant defense system of berries.