Effect of leaf removal and grapevine smoke exposure on colour, chemical composition and sensory properties of Chardonnay wines

Abstract

BACKGROUND AND AIMS The effect of leaf removal on the accumulation of smoke-related volatile compounds following exposure of grapevines to smoke under experimental conditions was investigated. METHODS AND RESULTS Chardonnay grapevines were defoliated around the bunches either before or after exposure to smoke. The effect of defoliation and/or smoke treatments on crop yield and vegetative growth was then evaluated. The extent of smoke taint in the resultant wines was determined by quantification of volatile phenols by gas chromatography-mass spectrometry and of guaiacol glycoconjugates by liquid chromatography-tandem mass spectrometry and by descriptive sensory analysis. The concentration of volatile phenols and guaiacol glycoconjugates was highest in wines corresponding to leaf removal pre-smoke exposure. These wines were characterised by intense ‘smoky’, ‘ashy’ and ‘burnt rubber’ attributes, whereas defoliation post-smoke exposure reduced the intensity of ‘cold ash’ and ‘ashy aftertaste’ attributes compared with that of other experimental treatments. CONCLUSIONS Leaf removal had a beneficial effect on wine aroma, enhancing the intensity of ‘fruit’ attributes. Where leaf removal was employed post-smoke exposure, resulting wines exhibited less intense ‘smoke’ characters than wines corresponding to grapevines subjected to smoke exposure. Leaf removal prior to smoke exposure, however, did not mitigate the intensity of smoke taint. SIGNIFICANCE OF THE STUDY This study improves the current understanding of the impact on fruit and wine composition of the exposure of grapevines to smoke. It informs grapegrowers and winemakers of viticultural practices that influence the severity of smoke taint in grapes and wine.