Preparation of a resveratrol-enriched grape juice based on ultraviolet C-treated berries

Grapes are rich in bioactive phenolics. However, most of them remain in the by-product after juice processing, and only a minor part pass to the juice. Our aim was to obtain a resveratrol-enriched white grape juice based on UVC-treated berries in combination with different conditions during juice production. Postharvest UVC treatment of berries enabled the further selective stilbenes enrichment of the juice, especially resveratrol. Macerating enzymes did not modify the phenolic profile but increased juice yield up to 30%, keeping its phenolic concentration, and thus reducing the phenolics remaining in the by-product. Maceration with Na2S2O5 was critical to increase the phenolic content in the juice whereas beta-cyclodextrin only tended to increase the stilbenes content. Optimum conditions for juice production (maceration for 2 h at 45 degrees C with 0.2% Na2S2O5) using UVC-treated grape berries significantly increased stilbenes concentration (up to 35-fold over the control), without affecting the sensory properties of the juice. The phenolic (resveratrol)enriched grape juice obtained here could be an ideal alternative to wine in the search of grape-derived health benefits. Industrial relevance: The aim of this study is to obtain a resveratrol-enriched grape juice by combining postharvest UV-C treatment of grape berries with several technological approaches in the juice processing. Results obtained indicate that maceration for 2 h at 45 degrees C with 0.2% Na2S2O5 using UVC-treated grape berries significantly increased phenolic concentration, especially stilbenes (up to 35-fold over the control), without affecting the sensory properties of the juice. The resveratrol-enriched juice has an added-value compared to the conventional ones and could exert more health benefits due to its improved phenolic profile. (C) 2009 Elsevier Ltd. All rights reserved.