Extraction of polyphenols from grape seeds and concentration by ultrafiltration

A solvent extraction method utilizing 50% ethanol and 50% water as solvent was used for the extraction of polyphenols from grape seeds. An additional ultrafiltlration step was also included to determine its beneficial effect. Various experimental conditions, such as solid to liquid ratio (0.1–0.25 g/ml), number of extraction stages (single, double and triple) and membrane pore size (0.22 and 0.45 μm) were investigated to optimize the extraction. When compared to a gallic acid standard, the extraction of grape seed polyphenols with a 0.2 g/ml solid to liquid ratio, double stage extraction and 0.22 μm membrane pore size were the optimal conditions. Under these conditions, the maximum amounts of polyphenols (11.4% of the total seeds weight) were recovered from grape seeds. From the standpoint of solvent toxicity, extraction efficiency and percentage of grape seed polyphenols recovered, this method proved to be adequate on all three counts.