Timing of leaf removal modulates tannin composition and the level of anthocyanins and methoxypyrazines in Pinot noir grapes and wines

Abstract

This study aimed to investigate the impact of leaf removal on concentrations of anthocyanin, tannin, and methoxypyrazines (MPs) in Pinot noir grapes and wines. Leaf removal after 7 days (LR7), 30 days (LR30), and 60 days (LR60) of flowering were compared with no leaf removal control (LRC). Grapes and resultant wines were analysed for tannin and aroma composition using liquid chromatography and two-dimensional gas chromatography-mass spectrometry. All leaf removal treatments increased anthocyanin concentration in grapes and reduced MP levels in grape stems compared to LRC, indicating the effectiveness of both early and late leaf removal. Leaf removal after 7 days and 30 days were more effective in enhancing colour density, polymeric pigments, and tannin concentration in wines. Higher grape skin tannin and anthocyanin concentrations, along with lower seed tannin concentration in berries, correlated with higher tannin concentrations in wines. LR7 showed significantly higher skin-originated tannin proportion than LRC, suggesting a useful tool to manage tannin extraction. Aroma composition of resultant wines was influenced by leaf removal, although these differences were not evident in the sensory evaluation.

Keywords: Anthocyanin; Grapes; Leaf removal; Methoxypyrazine; Pinot noir; Tannin; Wine.