Method of separating and recovering proteins from a protein solution

A preparative method of isolating a preselected whey protein or group of whey proteins from a whey protein solution by ion exchange, comprising the steps of

• (a) obtaining a whey protein solution having a protein concentration in the range of about 5% to about 20% by weight by ultrafiltration;
• (b) adjusting the pH of said whey protein solution to a preselected pH at which said whey protein or group of whey proteins selectively binds to an ion exchanger;
• (c) reducing the ionic strength of said whey protein solution by a method other than ultrafiltration, relative to a whey protein solution ultra filtered to the same protein concentration and subsequently adjusted to the same pH by addition of acid or base, while maintaining the protein concentration within the range of about 5% to about 20% by weight upon contact with but prior to adsorption onto a preselected ion exchanger;
• (d) contacting said whey protein solution with said ion exchanger, which may contain water, wherein said whey protein or group of whey proteins selectively binds to said ion exchanger;
• and
• (e) recovering either or both of the following:
• (1) the whey protein component selectively bound to said ion exchanger in step (d), and (2) the breakthrough whey protein component not bound to said ion exchanger in step (d);
• wherein step (b) and/or step (c) is optionally carried out after contact with the ion exchanger in step (d).