Optimization of the extraction of antioxidant compounds from grape seed from winemaking waste

An experimental design was conducted to optimize the extraction of grape seed polyphenols from the vinification residues of Merlot. A screening procedure was developed with three criteria (amount of organic solvent (25–75%), amount of seed (0.5–1.5 g), and extraction time (15–45 min)), two levels, and three central points, totaling 11 experiments, with seven critical attributes (total antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl, 2,2-azino-di-[3-ethylbenzthiazoline sulfonate], ferric reducing antioxidant power, and total phenols, flavonoids, and catechins), where the most appropriate levels were chosen to optimize extraction using the central compound design. The optimum conditions identified for extracting Merlot grape seed polyphenols were 33% grain alcohol, 1.7 g grape seed, and 15 min of extraction. These factors enabled extraction with a minimum of organic solvent and time, thereby maximizing the sample's antioxidant activity, while contributing to the reduction of the environmental impacts caused by wine production.