Content of resveratrol and total polyphenols in whole grape, reconstituted and sweetened juice sold in southern Brazil

Resumo

The quest for improved life quality has grown over the years, boosting research into the identification of bioactive substances in food. The polyphenols found in grapevines currently represent a broad area of research due to the benefits it has brought to people's health. This paper aimed to analyze whole grape, reconstituted and sweetened juice sold in the city of Bento Gonçalves and surrounding area to determine comparatively their levels of total polyphenols and resveratrol. This study consisted of eleven samples of grape juice from nine different brands. The samples were subdivided into whole grape juice, reconstituted grape juice and sweetened grape juice. The presence of resveratrol and polyphenols in each sample was determined by liquid chromatography and by reading a spectrophotometer at 280 nm, respectively. Variables with normal distribution were compared using the t-student test and Wilcoxon signed-rank test was applied to the nonparametric variables. Total polyphenol contents found in this study ranged from 18,50 to 107,95 mg/L. The highest average of polyphenols was found in the whole grape juice (85,71 mg/L), which is statistically higher (p = 0,009) than the one found in the sweetened juice (21,48 mg/L). The resveratrol content ranged from 0,45 to 2,60 mg/L, and no concentration was a found in the sweetened juice. The whole grape juice and the reconstituted juice showed the best results and therefore represent the best way to obtain these antioxidants and their benefits for the human body.