Postharvest treatment of table grapes with ultraviolet-C and chitosan coating preserves quality and increases stilbene content

• Red table grapes were treated with UV-C light and chitosan coating.
• Chitosan coating preserved visual quality and prevented decay by Botrytis cinerea.
• UV-C and storage at 20 ºC for 24 h before cold storage increased resveratrol content.
• Application of exogenous resveratrol solutions avoids growth of B. cinerea.
• UV-C and chitosan coating increased the resveratrol content while reducing decay.

Red table grapes were treated after harvest with ultraviolet-C light (UV-C) and chitosan coating, both alone and in combination. Effect of treatments on quality, fungal decay, and resveratrol content of grapes was studied. In preliminary trials, combination of UV-C with chitosan coating yielded better results compared with the same treatments applied alone. Therefore, further optimization was performed with combinations of the two treatments. Chitosan coating preserved brightness and visual quality of fruit while preventing decay by Botrytis cinerea. Furthermore, this coating treatment had no effect on respiration rate or resveratrol content of grapes. UV-C treatment combined with storage at 20 °C for 24 h before refrigerated storage led to increased resveratrol content and had no negative effects on the sensory quality of treated grapes when combined with chitosan coating. In contrast with endogenous resveratrol, the application of resveratrol solutions was effective for the prevention of growth of B. cinerea. Use of UV-C combined with chitosan coating followed by incubation for 24 h at 20 °C before refrigerated storage increased the resveratrol content, maintained sensory quality, and reduced fungal decay of red table grapes when compared to control grapes.