Solid-liquid extraction of phenolics from red grape skins

Abstract

For the characterization of grape cultivars, the profile and content of flavonoids are important because these compounds impact on grape and wine quality. A new extraction method for the recovery of flavonoids from grape skins was developed. The optimization of solid-liquid extraction of flavonoids was conducted, with respect to type of the organic solvent and their percentage in the extraction solvent as well as their extraction temperature and extraction time, using response surface methodology. Optimal conditions were obtained using 20 % acetonitrile as the organic modifier in extraction solvent, at an extraction temperature of 50 °C, an extraction time of 1 h in a single-step extraction and with a solid-to-solvent ratio of 1:80 g mL^-1. The calculated relative standard deviations for the optimal extraction method were very low, measuring less than 5 %. The new optimal extraction method is inexpensive, simple, fast, accurate and selective for the recovery of simple flavonoids.