Optimising UV-C preharvest light for stilbene synthesis stimulation in table grape: Applications

• UV-C preharvest treatment to increase grape stilbene is described for the first time.
• Maximum trans-resveratrol concentration was achieved 24 h after plant was treated.
• UV-C light dose around 10,000 J/m2 reached the maximum stilbene concentration.
• This technology is interesting for the health-promoting and anti-pathogenic properties of grape.

UV-C treatment has been studied for increasing stilbene in grape and inhibiting the development of spoilage microorganism. In this work, treatment application day (7, 5, 3 and 1 days previous to harvest) and light dose (from 966 to 27,990 J/m2) have been optimised together with storage conditions (20 °C–80% RH, 4 °C–60% RH and combined) when grapes were treated on plant with UV-C light. trans-Resveratrol and ε-viniferin were monitored in grapes after treatments. Maximum trans-resveratrol concentration was achieved after 24 h regardless of preharvest application day. It increased between 46 to and 22-folds. A dose lower than 10,000 J/m2 approximately seemed to increase trans-resveratrol. trans-Resveratrol was affected not only by the dose but also by how the dose was applied in terms of output power and exposure time. Cold storage keeps stilbene metabolism still until grapes reach a temperature which re-activates their synthesis.Industrial relevancePreharvest UV-C light treatment is an interesting stilbene inductor in table grapes on plant and during postharvest storage. Due to the health promoting and anti-pathogen properties of stilbenes, the use of this technology is interesting for both the consumer preferences and organic/viticulture point of view.