Timing of leaf removal modifies chemical and phenolic composition of Sauvignon Blanc wine

Douglas André Wurz,Marcus Outemane,Leo Rufato,Aike Anneliese Kretzschmar,Ricardo Allebrandt,Alberto Fontanella Brighenti,José Luiz Marcon Filho,Betina Pereira De Bem

doi:10.1051/bioconf/20170902027

Abstract

The objective of this work was to evaluate the effect of different defoliation times on the chemical and phenolic composition of Sauvignon Blanc wine in high altitude regions of Santa Catarina - Brazil. The experiment was conducted in the 2015 and 2016 seasons, in a vineyard located in the city of Sao Joaquim – Santa Catarina State. The defoliation was carried out during phenological stages: full bloom, berries pepper-corn size, pea-sized berries, veraison, 15 days after veraison and control without leaf removal. During harvest, severity of Botrytis cinerea was assessed by visual evaluation through a diagrammatic scale. For the wine samples from each season, total acidity (meq L−1 ), pH, total polyphenol content (mg L−1 of gallic acid) and color (Abs 420nm) were performed. For the wines of the 2015 harvest, phenolic compounds were analyzed: gallic acid, catechin, vanillic acid, P-coumaric acid and rutin. The chemical composition of Sauvignon Blanc wine was affected as a result of leaf removal timing, defoliation carried out in full bloom, berries pepper-corn size and pea-sized berries reduced total acidity and increased pH of the wines in both seasons. For wine color, in both seasons, it was found a greater yellow coloration in wines originated from grapes where the plants were not defoliated. The increase of yellow coloration is due to the oxidation of catechins and epicatechins, which is related to the increase of botrytis bunch rot. In the 2015 season there were no influence of leaf removal timing in total polyphenols, however, in the 2016, the defoliation performed in full bloom resulted in lower polyphenols contents. Wines from non-defoliated plants presented higher values of catechin, rutin, P-coumaric acid and gallic acid, related to yellow coloration of wines and greater susceptibility to darkening and oxidation. For vanillic acid, wines from non-defoliated plants have the lowest values, this compound is important in wine preservation. Leaf removal is an important management technique in high altitude regions of Santa Catarina - Brazil, it improves wine chemical composition, and if carried out during the stages of full bloom, pepper corn berries and pea-sized berries can reduce the severity of Botrytis bunch rot; and avoid the formation of phenolic compounds related to the processes of oxidation and darkening.

Highlights

Highland regions of Santa Catarina State, Brazil, have been acquiring great importance due to the high potential for wine production from Vitis vinifera L. cultivars [1,2,3]
To improve our understanding about vineyard practices, the present study aims to investigate the effect of different leaf removal time on the botrytis bunch rot disease development and chemical-phenolic composition c The Authors, published by EDP Sciences
Leaf removal associated with high solar radiation provides a reduction in berries acidity due to the greater degradation of malic acid [24, 25]

Summary

Introduction

Highland regions of Santa Catarina State, Brazil, have been acquiring great importance due to the high potential for wine production from Vitis vinifera L. cultivars [1,2,3]. Basal leaf removal may be employed to improve air and light exposure around clusters, as well as to open access to disease- and pest-control chemicals [7]. It is a vineyard practice carried out in all wine-growing regions, which is usually applied between the setting and veraison phenological stages of the grapevine [8, 9]. An effect generally associated with basal leaf is a reduce incidence of bunch rot [11]. An effect generally associated with basal leaf removal is a drop in titratable acidity [12, 13]

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