Effects of Fruit Zone Leaf Removal on the Concentrations of Phenolic and Organic Acids in Istrian Malvasia Grape Juice and Wine

Phenolic acids, represented by hydroxycinnamic and hydroxybenzoic acids and their derivatives, are the most abundant phenolic compounds in grape juice and wine of white grapevine cultivars. The effects of fruit zone leaf removal on the concentration of hydroxycinnamic, hydroxybenzoic and organic acids of cv. Istrian Malvasia grape juice and wine are investigated in this study. Fruit zone leaf removal was applied at three different phenological stages: before blooming, at berry set and at veraison. Control treatment without leaf removal was also included. At veraison two intensities of leaf removal were applied. Phenolic and organic acids were identified and quantified using high-performance liquid chromatography. Juice samples from the grapes treated at the stages before blooming and berry set had the lowest concentrations of tartaric acid and the highest concentrations of malic acid, while juices from veraison stage treatments had the lowest concentrations of malic acid and the highest concentrations of tartaric acid. Before blooming treatment significantly lowered the concentration of all hydroxycinnamic and hydroxybenzoic acids in grape juice in comparison with other investigated treatments, which did not affect the concentration of total hydroxycinnamic acids considerably. The concentration of hydroxybenzoic acids in grape juice was lower in veraison treatments in comparison with berry set and control treatments. The concentrations of hydroxycinnamic, hydroxybenzoic and organic acids in wine followed the same trends as observed in grape juice. it is concluded that the concentration of phenolic and organic acids in grape juice and wine of white grapevine cultivars can be managed with the timing of fruit zone leaf removal according to the desired wine style.