Preparation of resveratrol-enriched grape juice from ultrasonication treated grape fruits

• We examined changes in the amounts of resveratrol contents in post-harvested grapes by ultrasonication treatment.
• In all three tested grape cultivars, the amounts of resveratrol increased by an ultrasonication treatment.
• The sweetness of the treated grapes did not change significantly.
• We report ultrasonication treatment as an effective method for producing resveratrol-enriched grape juice.

Grape (Vitis spp.) is a major source of resveratrol that can be eaten directly or after making jam, jelly, wine and juice. Resveratrol (3,5,4′-trihydroxystilbene) has a profound positive influence on human health, including anti-carcinogenic, anti-cancer, anti-inflammatory, and anti-ageing effects and the ability to lower blood sugar. During industrial production of grape juice, resveratrol is lost because of the use of clarifying agents and filtration; therefore, commercial grape juice contains very low amounts of resveratrol. In this study, we investigated the accumulation of resveratrol in grape juice prepared from three varieties of grape, viz. Campbell Early, Muscat Bailey A (MBA) and Kyoho, following post-harvest ultrasonication cleaning for 5 min and 6 h of incubation in the dark at 25 °C. This process resulted in the amounts of resveratrol increasing by 1.53, 1.15 and 1.24 times in juice prepared from Campbell Early, MBA and Kyoho, respectively, without changing the amounts of total soluble solids. Overall, our results indicate that ultrasonication treatment of post-harvested grape fruits can be an effective method for producing resveratrol-enriched grape juice as well as cleaning grapes thoroughly.