Effects on Chemical Composition and Phenolic Compounds of Mustand Wines Produced with Remove Approximately 45 of Leaves of Narince Grapes Grown in Three Territories

Abstract

This study was conducted to determine the effects of excessive leaf harvest treatments (control, 6 harvests) on must and wine composition of Narince grapes grown in Tokat City Center (Central), Erbaa and Niksar districts in 2014. With 6 leaf harvests, approximately 45% of the leaves were removed. As compared to control treatments, leaf harvest treatments reduced grape yields (Central, 40.8%; Erbaa, 63.6%; Niksar, 39.6%). The grapes harvested at industrial maturity stage were processed into wines with microvinification method. The pH, total soluble solid contents (TSSC), total acidity, specific gravity, ethyl alcohol, volatile acid, reducing sugar, total sulphur dioxide, total phenolics, total flavonoids and some phenolic compounds of the must and wines were determined. In all three territories, leaf harvest treatments increased TSSC, total acidity and ripening index of the must; ethyl alcohol content of the wine; specific gravity, total phenolics and flavonoids of both the must and the wine, but reduced sensory analyses scores. Total phenolics and flavonoids generally increased with increasing altitudes and resultant UV radiations. It was concluded based on these findings that increases in total temperatures of 37 C and over accelerated the disintegration of Narince phenolics. Thus 37 C was identified as the critical temperature for phenolic disintegration. Among 8 different individual phenolics looked for in present study, vanillic acid and catechin were identified as the major ones. It was concluded based on present findings that leaf harvest treatments reduced the must and wine quality parameters of Narince grapes.