Postharvest UV-B radiation as a dual strategy to improve microbial safety and phenolic quality in wine grapes

Abstract

UV-B radiation is an important environmental regulator of grapevine phenolic metabolism, but its controlled postharvest use and interaction with fruit health status remain poorly understood. Healthy and Botrytis cinerea-infected Tempranillo and Garnacha Blanca grapes were treated after harvest with 0.18 or 1.40 GJ m^–2 UV-B. Skin phenolic composition was analysed by UV-visible spectrophotometry and UPLC-MS/MS, assessing global indices and individual flavonols, flavanols, stilbenes, phenolic acids, and anthocyanins. The phenolic response was moderate but clearly dependent on dose, cultivar and health status. The highest dose significantly increased flavonols, including quercetins and kaempferols, and stilbenes, especially in healthy grapes, confirming activation of photoprotective and antioxidant-defence pathways. Tempranillo mainly showed increased flavonols, with positive implications for copigmentation and colour stability. Garnacha Blanca displayed dose-dependent accumulation of trans- and cis-resveratrol and piceatannol, reflecting a phytoalexin-based response. Infected grapes showed a weaker or negative response, including reduced anthocyanins, although some compounds remained stable or increased. Postharvest UV-B can therefore selectively improve grape antioxidant and technological potential when fruit physiological integrity is preserved.

References

1. Sanz Cervera, S. A. Postharvest UV-B Radiation as a Dual Strategy to improve Microbial Safety and Phenolic Quality in Wine Grapes. Recording of the presentation delivered at Enoforum Spain 2026, Zaragoza, 20–21 May 2026. Available soon on Infowine Premium: https://vinidea.it/es/brand/infowine/

Acknowledgements

This work is part of project PID2023-150695NB-I00, funded by MCIU/AEI/10.13039/501100011033/ERDF, EU.