Alterações na composição, no potencial antioxidante e nas propriedades biológicas do suco produzido com uvas Vitis labrusca, cv. Bordô, tratadas com radiação UV-C.

Abstract

It is widely known that the application of UV-C radiation at post-harvest contributes to reducing fruit rot, by the reduction of microorganisms and induce defense mechanisms, and stimulating secondary metabolism. Thus, it is expected that the application of moderate doses of UV-C can act as a promoter of the synthesis and accumulation of bioactive molecules, changing the vegetable composition as well as the functional potential properties. In this context, we have attempted to maximize the concentration of these bio-molecules in the juices, treating Vitis labrusca grapes, cv. cultivated in Pelotas region (South of RS). After the harvest of the grapes, 50% of the grapes batches were kept untreated (no application of UV-C) and 50% were treated with UV-C at a dose of 7.4 kj.m2-1 hormic. From the grapes with treatment and store in room temperature in dark for 23h, the juice was elaborated on a steam extractor, which was the material for analysis. According to the results, it was found that the UV-C interferes in the physicochemical characteristics of the juices. In relation to phenolic compounds, we found that quercetin followed by trans-resveratrol, phydroxycinnamic acid, malvidin and delphinidin were the compounds that increase their concentrations, and catechin, epicatechin and kaempferol have shown small quantities in the treated juice, without detection of cyanidin. The juices elaborated with treated grapes with UV-C showed mean values of total phenolic compounds, anthocyanins and antioxidant activity in vitro and in vivo significantly (p £ 0.05) higher than the control juice. The control juice and the juice elaborated with grapes treated with UV-C, guaranteed around 55% and 72%, respectively, for the survival of yeast cells against damage caused by the stressor agent, hydrogen peroxide. Existed significant correlation between the antioxidant activity in vivo and in vitro and the content of total phenol compounds (R = 0.91) and total anthocyanins (R = 0.96). The juices of grapes, either the elaborated with grapes treated with UV-C or not, did not promote weight gain, did not increase blood glucose levels, but have increased the coefficient of alimentary efficiency on the studied animals. The oxidative damage caused to animals by hyperlipidic diet were reduced with increasing of the antioxidant enzyme activities, as well as by the increased of the total antioxidant capacity provided by the grape juice of cv. Bordô treated with UV-C. Concludes that the UV-C treatment promote alterations in the phenolic metabolism of the grape, which results in grape juice from Vitis labrusca cv. Bordô, cultivated in the region of Pelotas, with high antioxidant potential and beneficial biologic responses.