Abstract
Ultraviolet (UV) radiation strongly influences grape composition, but only a few studies have focused on how this influence is conserved in the resulting wines. Here we analyzed to what extent the changes induced by exposing Tempranillo grapes to UV radiation from budbreak to harvest were conserved in wine. By using different cut-off filters and lamps, we differentiated the effects of ambient levels of UV-A and UV-B wavelengths, as well as the effects of a realistic UV-B enhancement associated with climate change. Among phenolic compounds, the most consistent responses to UV were those of flavonols (particularly quercetin-, kaempferol-, isorhamnetin- and myricetin-glycosides), which significantly increased in wines whose grapes had been exposed to a synergic combination of UV-A and UV-B radiation. This confirms that flavonols are the phenolic compounds most reliably conserved from UV-exposed grapes to wine, despite the possible influence of the winemaking process. Flavonols are important compounds because they contribute to wine co-pigmentation by stabilizing anthocyanins, and they are interesting antioxidants and nutraceuticals. Hydroxycinnamic acids also increased under the same UV combination or under UV-A alone. Wine VOCs were much less reactive to the UV received by grapes than phenolic compounds, and only esters showed significantly higher values under (mainly) UV-A alone. This was surprising because (1) UV-A has been considered to be less important than UV-B to induce metabolic changes in plants, and (2) esters are produced during winemaking. Esters are relevant due to their contribution to the fruity aroma in wines. In general, the remaining phenolic compounds (stilbenes, flavanols, hydroxybenzoic acids, and anthocyanins) and VOCs (alcohols, hydrocarbons, and fatty acids), together with wine color and antioxidant capacity, showed inconsistent or non-significant responses to UV radiation. These results were summarized by a multivariate analysis. Our study opens up new possibilities to artificially manipulate UV radiation in grapevine cultivation to improve both grape and wine quality.
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Claims 9
Claim · model-written summary
Combined UV-A and UV-B exposure significantly increased flavonols in wine from exposed grapes.
- Taxon
- grapese0
- Treatment
- a synergic combination of UV-A and UV-B radiatione0
- Outcome
- flavonolse0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“flavonols (particularly quercetin-, kaempferol-, isorhamnetin- and myricetin-glycosides), which significantly increased in wines whose grapes had been exposed to a synergic combination of UV-A and UV-B radiation.”
Claim · model-written summary
Hydroxycinnamic acids increased under combined UV-A and UV-B exposure.
- Taxon
- Tempranillo grapest0
- Treatment
- same UV combinatione0
- Outcome
- Hydroxycinnamic acidse0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“Hydroxycinnamic acids also increased under the same UV combination or under UV-A alone.”
t0“Tempranillo grapes”
Claim · model-written summary
Hydroxycinnamic acids increased under UV-A alone.
Not reportedComparator
Verbatim
e0“Hydroxycinnamic acids also increased under the same UV combination or under UV-A alone.”
t0“Tempranillo grapes”
Claim · model-written summary
Wine volatile compounds were less responsive to grape UV exposure than phenolics.
Verbatim
e0“Wine VOCs were much less reactive to the UV received by grapes than phenolic compounds”
Claim · model-written summary
Esters were significantly higher under mainly UV-A alone.
Not reportedComparator
Verbatim
e0“only esters showed significantly higher values under (mainly) UV-A alone.”
t0“Tempranillo grapes”
Claim · model-written summary
Remaining wine phenolic classes had inconsistent or nonsignificant responses to UV radiation.
- Taxon
- Tempranillo grapest0
- Treatment
- UV radiatione0
- Outcome
- stilbenes, flavanols, hydroxybenzoic acids, and anthocyaninse0
- Direction
- inconsistent or non-significante0
Not reportedComparator
Verbatim
e0“the remaining phenolic compounds (stilbenes, flavanols, hydroxybenzoic acids, and anthocyanins) and VOCs (alcohols, hydrocarbons, and fatty acids), together with wine color and antioxidant capacity, showed inconsistent or non-significant responses to UV radiation.”
t0“Tempranillo grapes”
Claim · model-written summary
Alcohols, hydrocarbons and fatty acids had inconsistent or nonsignificant UV responses.
- Taxon
- Tempranillo grapest0
- Treatment
- UV radiatione0
- Outcome
- alcohols, hydrocarbons, and fatty acidse0
- Direction
- inconsistent or non-significante0
Not reportedComparator
Verbatim
e0“the remaining phenolic compounds (stilbenes, flavanols, hydroxybenzoic acids, and anthocyanins) and VOCs (alcohols, hydrocarbons, and fatty acids), together with wine color and antioxidant capacity, showed inconsistent or non-significant responses to UV radiation.”
t0“Tempranillo grapes”
Claim · model-written summary
Wine color and antioxidant capacity had inconsistent or nonsignificant UV responses.
- Taxon
- Tempranillo grapest0
- Treatment
- UV radiatione0
- Outcome
- wine color and antioxidant capacitye0
- Direction
- inconsistent or non-significante0
Not reportedComparator
Verbatim
e0“wine color and antioxidant capacity, showed inconsistent or non-significant responses to UV radiation.”
t0“Tempranillo grapes”
Claim · model-written summary
The authors propose manipulating UV in grapevine cultivation to improve grape and wine quality.
VitisOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Our study opens up new possibilities to artificially manipulate UV radiation in grapevine cultivation to improve both grape and wine quality.”
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