a method for producing a proanthocyanidin extract is described . the method comprises : providing a volume of proanthocyanidin - containing liquid feedstock ; passing the proanthocyanidin - containing liquid feedstock to an ultrafiltration feed tank ; filtering the material in the ultrafiltration feed tank through an ultrafiltration membrane system to fractionate the material into a proanthocyanidin - reduced permeate stream and a proanthocyanidin - enriched retentate stream ; collecting the proanthocyanidin - reduced permeate stream ; and passing the proanthocyanidin - enriched retentate stream to the ultrafiltration feed tank until the volume of proanthocyanidin - containing liquid feedstock is exhausted and thereafter collecting the proanthocyanidin - enriched retentate stream .