Application of UV-B radiation in pre- and postharvest as an innovative and sustainable cultural practice to improve grape phenolic composition
Ultraviolet radiation (UVR) is a minor part of the solar spectrum, but it represents an important ecological factor that influences many biological processes related to plant growth and development. In recent years, the application of UVR in agriculture and food production is emerging as a clean and environmentally friendly technology.
In grapevine, many studies have been conducted on the effects of ambient levels of UVR, but there are few considering the effects of UV-B application on grape phenolic composition under commercial growing or postharvest conditions.
In this study, two kinds of UV-B applications were performed on Tempranillo grapes. On one hand, grape clusters at commercial maturity were supplemented with UV-B for five days before harvest, using a tractor-mounted lamp. On the other hand, postharvest bunches were irradiated with UV-B using an automated postharvest application technology.
In both cases, after UV-B application, the overall levels of phenolic compounds were analyzed, as well as the phenolic profile of the grape skins. The main response to the UV-B treatment in preharvest was an increase in flavonols, mainly quercetins. In the postharvest application, both total phenol and flavonol contents increased, while hydroxycinnamic acid derivatives showed an opposite trend, with higher concentrations in the control treatment. In neither treatment did the sugar content or acidity of the grapes change.
In conclusion, the application of UV-B, both in pre- and postharvest, improved the phenolic quality of grape skins, mainly through the increase in flavonols. Our study opens new possibilities to realistically introduce the mechanical application of supplemental UV-B radiation as an additional agricultural practice under commercial field conditions at crop scale (pre- and postharvest), in order to improve grape quality. This could be of great importance in the context of climate change in which we are immersed.
Issue: ICGWS 2023
Faculty of Science and Technology, University of La Rioja. 26006 Logroño (La Rioja), Spain