Otimização da extração de compostos fenólicos e antocianinas do bagaço da uva e estudo de estabilidade acelerado

Abstract

In Brazil, most of the pomace generated in wine production is treated as low-value waste. However, this product contains phenolic compounds that have numerous biological activities. In this way, different methods can be used in the extraction of these substances, but most are costly and have been replaced by more sensitive, selective, fast, and environmentally safe methodologies. The objective of this study was to optimize the extraction of phenolic compounds and anthocyanins using an ultrasound system from grape pomace and to perform an accelerated stability study. The pomace was obtained from the wine production of the Bordeaux grape, Vitis labrusca species, and then it was lyophilized, ground, and submitted to ultrasound-assisted extraction. The factors evaluated in the experimental design were the concentration of ethanol (0 to 70 %), the concentration of citric acid added to the solution (0 to 4 %), the ultrasound power (1000 to 4500 W/L), and the mass concentration (1 to 15 %), totaling 28 trials. Among the conditions evaluated, through the analysis of monomeric anthocyanins and phenolic compounds, the most efficient extraction occurred when 3838 W L-1 of power, 3.24 % citric acid, 70 % ethanol, and mass concentration of 1 % were applied. In the optimized extract, the anthocyanin and phenolic content was 16.76 ± 2.31 mg malvidin3-glycoside equivalent and 65.15 ± 4.35 mg gallic acid equivalent per gram of residue, respectively. In addition, antioxidant activities were determined, with results of 43.70 ± 6.25 μmol Trolox g-1 equivalent by ABTS and 205.73 ± 10.41 μmol of Fe (II) g-1 by FRAP, and antimicrobial, where inhibitory activity against Gram-positive and negative bacteria was observed. The presence of resveratrol was determined by highperformance liquid chromatography. A stability study was carried out and was verified that the concentrated liquid extract remained stable for 35 days. When used as a food adjuvant, it provided prolonged stability to the yogurt-like food product, in which it was applied, compared with it without the addition of extract. Therefore, the use of an ultrasound system proved to be a suitable alternative for the extraction of phenolic compounds and anthocyanins from the pomace of the Vitis labrusca grape, where the extract obtained proved to be a promising antioxidant and con-servant and that can be used safely and sustainably in food products.