Abstract: A production method for an MP whey is provided, that enables preparation of both of a high GMP-content composition and a usable MP whey from an ordinary MP whey. The problems can be solved by a production method for a glycomacropeptide-containing composition, that includes a step of acquiring a solution containing glycomacropeptide, that includes a glycomacropeptide content of 10% by weight or higher in the protein total amount by condensing and/or applying diafiltration to a microparticulated whey solution.

Abstract: A method for fractionating whey proteins, including: preparing a solution including a first whey protein and a second whey protein and separating the first whey protein and the second whey protein with a membrane; wherein the first whey protein forms a complex with at least one of carbonate ion, hydrogen carbonate ion, a light metal ion, and a transition metal ion; and the second whey protein satisfies at least one of the following (1) and (2): (1) the second whey protein forms no complex with any of the carbonate ion and the hydrogen carbonate ion; (2) the second whey protein forms no complex with any of the light metal ions and the transition metal ions.