A process in which olive polyphenol concentrate is obtained from a by-product of olive oil extraction comprising the steps of: a) mixing the by-product with a polar solvent to give a by-product/solvent mixture; b) extracting polyphenols from the by-product/solvent mixture to give an olive polyphenols solution and extracted solids; and c) concentrating the olive polyphenols solution using membrane separation techniques to yield an olive polyphenols concentrate wherein the concentration of polyphenols present is at least 10 wt % and wherein the process further includes a defatting step.