Microclimate of Grape Bunch and Sunburn of White Grape Berries: Effect on Wine Quality

Abstract

This research aimed to evaluate the composition of wines made with white grapes which are particularly susceptible to sunburn symptoms due to the absence of anthocyanin. Sunburn is a complex physiological dysfunction leading to browning or necrosis of berry tissues. In vintage 2021, the canopy of ‘Verdeca’ grapevines grown in Salento, South Italy, was differently managed by sun exposing or shading the bunches. Micrometeorological conditions were studied at different levels. Grapes were vinified, comparing the winemaking with and without skin maceration. The vegetative-productive balance of plants was not substantially modified. On the contrary, a significant effect was observed on the quality and quantity of grapes produced: smaller berries with sunburn symptoms were found on unshaded bunches. This influenced the percentage distribution among skin, pulp and seeds, causing a decrease in must yield of up to 30%. The pH was significantly higher in macerated wines made using shaded grapes, due to a lower titratable acidity and to significant impacts on the acid profile. Obviously, maceration produced a higher extraction of phenolics in wines, which reached their maximum in wines made with sunburned grapes. The absorbance at 420 nm, index of yellow color, was also significantly higher in sunburned grapes, indicating greater oxidation. Even though excessive grape sun-exposure could negatively affect the perception of white wines made without maceration (resulting in more oxidative character), the sensory quality of orange/amber wines was not significantly impacted by the presence of sunburned grapes. Thus, this winemaking technique could be particularly interesting to set up a production strategy adapted to viticultural regions strongly affected by climate change.

Berry shrivel in grapevine: a review considering multiple approaches

“…Sunburn symptoms range from brown or necrotic spots on berry skins to complete desiccation, depending on the intensity and duration of heat stress ( Rustioni et al , 2014 ). Berry temperatures >45–50 °C can induce brown and necrotic spots on berry skins due to oxidative stress, causing phenolic oxidation associated with cell decompartmentalization and possibly resulting in berry cracking and desiccation ( Rustioni et al , 2014 , 2023 ; Müller et al , 2023 ).…”

Summer pruning in Mediterranean vineyards: is climate change affecting its perception, modalities, and effects?

“…As regards the actual need for leaf removal, if worries related to multiple summer stresses are increasing (Palliotti and Poni, 2015), then maintaining some leaf cover around the clusters is at least advisable. Recent work on the relationship between the timing of leaf removal and the susceptibility to sunburn (Diago et al, 2012;Ferrari et al, 2017;Gambetta et al, 2019;Gambetta et al, 2021;Rustioni et al, 2023) concluded that early leaf removal (i.e., at fruit set rather than at veraison) will reduce the incidence of sunburn. Moreover, extensive analytics performed by (Gambetta et al, 2021) for photo-protectant compounds (i.e., flavonoids, carotenoids, and chlorophylls) demonstrated that all molecules are especially receptive to the light stimulus during the green phase of berry growth.…”

Effects of Climate Conditions before Harvest Date on Edamame Metabolome

“…In grape-producing regions, such as those in Europe, there are differences in the grape quality from field to field, and this difference is thought to be due to various environmental factors, including the microclimate called terroir [ 10 ]. Previous studies reported that the temperature of the field environment affects the coloration of grapes and that excessive sunlight has a negative effect on the amount of flavonoids and flavor-related components [ 11 , 12 ]. Metabolome analysis has also revealed that sunlight causes changes in the amounts of other metabolites in grapes [ 13 , 14 ].…”