Impact of preharvest and postharvest treatment combinations on increase of stilbene content in grape

Abstract

Aims : Stilbene-enriched grape is an interesting new food product with numerous health-promoting properties, mainly due to its high added-value compound content, notably resveratrol. The aim of this study was to evaluate the effects of different elicitors, alone or in combination with ultraviolet C light (UVC) postharvest treatment, on stilbene concentration in grapes. Methods and results : Three preharvest treatments were tested, namely benzothiadiazole, (BTH), methyl jasmonate (MEJA) and chitosan (CHIT). After harvesting, these treatments were combined with UVC postharvest treatment. The stilbene extraction method was validated method. Moreover, and grape quality was evaluated. Of the preharvest treatments, only BTH significantly increased trans-resveratrol concentration in grape, but this appears to be linked to a ripening delay. When pre- and postharvest treatments were combined, only the MEJA-UVC combination was successful in reducing by three days the day of maximum induction of stilbenes (trans resveratrol and piceatannol). Conclusion: The MEJA-UVC combination reached similar grape trans-resveratrol contents than UVC alone, but additionally the time to reach maximum trans-resveratrol after the UVC treatment was reduced by three days and therefore grape quality was preserved. Significance and impact of the study: The achieved results provide a potential treatment combination that allows functional grapes to be obtained in a shorter period than with UVC light alone, making it more applicable.