Investigação do potencial biotecnológico do bagaço de uva (vitis vinífera l.) variedade benitaka, cultivada no município de São João do Piauí, PI

Abstract

Objective: To investigate the biotechnological potential of grape pomace from the Benitaka variety, cultivated in São João do Piauí, Piauí, through scientifically recognized analytical methodologies with the aim of recognizing the major groups of metabolites responsible for antioxidant activity. Metodology: Samples of grape (Vitis vinifera L.) from the Benitaka variety were collected from the Vine Complex at Marrecas settlement (2011/2012 harvest season) in the municipality of São João do Piauí, Piauí state. After harvest, the grapes were cleaned and pressed using an industrial depulper separating the pomace (skin and seeds) and pulp for the extraction of grape juice. After this extraction, the pomace was dried in an air circulation oven and was triturated. The powder was then subjected to chemical analysis for the determination of vitamin C, anthocyanins, minerals, microbiological quality, lipide profile and toxic potential. Subsequently, from the powder obtained, extractions using different solvents were performed and the extracts were subjected to toxicological analysis, total phenolics, total flavonoids, total tannins, antioxidant activity in vitro by DPPH• and autoxidation system β-carotene/linoleic acid methods, oxidative stability of soybean oil and identification and quantitation of polyphenols for HPLC-UV. The results were reported as means and standard deviation (n = 3). Analysis of variance and Tukey's test were conducted to determine the differences among means, using SAS®. Statistical significance was declared at P<0.05. Results: The results showed that the powder obtained from grape pomace had an amount of total dietary fiber (46.17g/100g) which stood out quantitatively compared to the content of carbohydrate (29.2g/100 g), protein (8.49g/100g), and lipids (8.16g/100g). The total energy was 224Kcal/100g. Insoluble fiber (79%) was higher than the soluble fraction (21%). The content of vitamin C was 26.25 mg ascorbic acid/100g and anthocyanins were 131mg/100g. The minerals iron (18.08mg/100g), potassium (1.40mg/100g), zinc (0.98mg/100g), manganese (0.82mg/100g) and calcium (0.44mg/100g) were present at higher concentrations. The lipid fraction of grape pomace was composed mainly of linoleic acid, PUFA (89.61%) >MUFA (21.37%) >SFA (18.46%). The extraction yield varied from 6.85% to 45.5%, depending on the extraction solvent. The lowest yield was found in pomace extracted with acetone and methanol presented the highest value. The total phenolic content, total flavonoid and total tannin varied depending on the extraction solvent. The ethanolic and acetonic extracts of grape pomace interacted with the stable free radical DPPH• efficiently, with averages IC50 of 0.31 µg/mL and 0.39 µg/mL; however they did not differ statistically to values for quercetin (0.22 µg/mL) and BHT (0.11 µg/mL). The extracts efficiently protected the oxidation of emulsified linoleic acid, with averages IC50 of 0.34 µg/mL to 0.36 µg/mL; this was similar to the synthetic antioxidant BHT. Ethanolic extract of grape pomace increased the induction time of soybean oil with an average of IC50 ranging from 0.34 µg/mL to 0.36 µg/mL. The most abundant phenolic compound was isoquercitrin (12.94 mg/100g), followed by rutin (7.54 mg/100g), quercetin (5.4 mg/100g) and resveratrol (2.5 mg/100g). Conclusion: The results presented in this study demonstrate that grape pomace from the Benitaka variety is rich in nutrients and phenolic compounds and showed a high antioxidant potential, something which contributes to its high value as a fruit byproduct and a fact that encourages the prospect of its commercialization as a natural antioxidant.