Phenolic characteristics acquired by berry skins of Vitis vinifera cv. Tempranillo in response to close-to-ambient solar ultraviolet radiation are mostly reflected in the resulting wines.

BACKGROUND: It is widely recognized that ambient levels of solar ultraviolet (UV) radiation strongly influence the phenolic composition of grape skins. However, it is unknown to what extent this influence is reflected in the resulting wines.

RESULTS: Tempranillo grapevines were exposed or non-exposed to close-to-ambient solar UV levels by using appropriate filters, and the phenolic profiles and antioxidant capacity of both grape skins and the resulting wines were analyzed. A total of 47 phenolic compounds were identified in skins and wines, including flavonols, anthocyanins, flavanols, stilbenes, and hydroxycinnamic and hydroxybenzoic acids. In UV-exposed grape skins, flavonols and anthocyanins increased, while flavanols and hydroxybenzoic acids showed no significant change. These characteristics were conserved in the resulting wines. However, for stilbenes, hydroxycinnamic acids, and antioxidant capacity, the effect of UV on grape skins was not conserved in wines, probably due to changes during winemaking. In addition, color intensity, total phenols, and total polyphenol index of wines elaborated from UV-exposed grapes increased (although non-significantly) in comparison with those made from non-UV-exposed grapes.

CONCLUSION: The phenolic composition of grape skins exposed to close-to-ambient solar UV could predict, to some extent, the phenolic composition of the resulting wines, particularly regarding higher contents of flavonols and anthocyanins. Thus, manipulating the UV radiation received by grape skins could improve wine quality by positively influencing color stability and healthy properties. To our knowledge, this is the first study in which the effects of solar UV radiation on phenolic composition have been assessed from grape skins to wine. This article is protected by copyright. All rights reserved.