Postharvest induction modeling method using UV irradiation pulses for obtaining resveratrol-enriched table grapes: A new "functional" fruit?

A modeling method for the induction of resveratrol synthesis by UV irradiat ion pulses in Napoleon table grapes is proposed, The method is based on the combination of four main parameters: irradiation power (IW), irradiation t ime (IT), irradiation distance (ID), and number of elapsed days to achieve the highest resveratrol accumulation (D-m). Maximum resveratrol content (11 -fold higher than untreated grapes) was achieved using the combination: IW = 510 W, IT = 30 s, ID = 40 cm, and D-m = 3 days. Sensory characteristics a nd main features of irradiated grapes (color, weight, firmness, flavor, siz e, ripening index and vitamin C content) remained unaltered after 1 week of storage. UV induction signal migrated to the hidden side of the grape skin with a delay of 3 days as compared to the directly irradiated side. Phenol ic compounds were not detected in Napoleon grape flesh. Resveratrol content per standard serving (200 g) of irradiated grape was about 3 mg, an amount more than 10-fold higher than that of untreated Napoleon grapes. This mean s that a serving of irradiated grape (unpeeled) could supply the resveratro l content equivalent to 3 glasses of a red wine with high resveratrol conte nt (approximate to 1 mg/glass). Therefore, controlled UV irradiation pulses are useful as a simple postharvest treatment (and alternative to genetic e ngineering) to obtain possible "functional" grapes (with enhanced health-pr omoting properties) as a dietary source of high resveratrol content.