Abstract
Basal defoliation, as one of the most common viticulture management practices to modify fruit zone microclimates, has been widely applied aiming at improving wine quality. Wine aroma contributes greatly to wine quality, yet the effects of basal defoliation on wine aromas show discrepancies according to previous studies. This study is a meta-analysis performed to dissect the factors related to the influence of basal defoliation on volatile compounds in wine. Timing of basal defoliation plays an important role in the concentration of varietal aromas in wine. Pre-veraison defoliation induces an increase in β-damascenone and linalool as well as a reduction in 3-isobutyl-2-methoxypyrazine (IBMP). The effects of basal defoliation on certain volatile compounds relative to fermentation aromas in wine (1-hexanol, β-phenylethanol, 2-phenylethyl acetate, decanoic acid, and ethyl octanoate) depend on grape maturity. There are also other factors, such as cultivar and climate conditions, that might be responsible for the effect of basal defoliation on wine aromas. The concentrations of isobutanol, isoamyl alcohol, hexanoic acid, and octanoic acid as well as ethyl isobutyrate, ethyl hexanoate, ethyl isovalerate, and ethyl decanoate in wine are not markedly affected by basal defoliation. Due to limited studies included in this meta-analysis, more trials are needed to confirm the current findings.
Highlights
Basal defoliation, defined as the practice of leaf removal in the fruit zone, is one of the most common viticulture management practices to modify fruit zone microclimates
Carotenoids serving as the precursors to both free and bound C13 -norisoprenoids can be catalyzed by carotenoid cleavage dioxygenase (CCD) to produce aroma apocarotenoids including β-damascenone, β-ionone, geranylacetone, α-ionone, vitispirane A, vitispirane B, and TDN [33,34]
Attention was paid to two C13 -norisoprenoids, β-damascenone and β-ionone. β-Damascenone contributes to floral, sweet, and fruity notes of wine, and it can enhance fruity notes of ethyl cinnamate and caproate as well as mask the herbaceous aroma of 3-isobutyl-2-methoxypyrazine (IBMP) in wine [35]. β-Ionone has been widely studied for its typical violet odor [36,37]
Summary
Basal defoliation, defined as the practice of leaf removal in the fruit zone, is one of the most common viticulture management practices to modify fruit zone microclimates (sunlight exposure, fruit zone temperature, and fruit zone air circulation). Under the background of global warming, the rise in average temperature and the associated increase in heat accumulation have caused earlier harvest dates in many regions [10]. Late apical defoliation, removing leaves located above the bunch zone between veraison and harvest, has been reported as an effective method to delay harvest. Since young leaves at the top of the main shoot are the main contributors to the accumulation of sugars in the fruit between veraison and harvest, this technique
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