Provided is a process for the demineralisation and fractionation of whey or raw milk comprising the steps of: a) subjecting the whey or raw milk to ultrafiltration to provide a retentate fraction and a whey permeate； b) concentrating the whey permeate to nanofiltration to provide a concentrated lactose rich retentate； c) subjecting the nanofiltration retentate to ion permeation chromatography at elevated temperatures of between 50 degree C and 80 degree C, using an appropriate resin； and d) eluting the nanofiltration retentate in various fractions from the resin using water as the eluant.
