Ion exchange is a unit operation which has several applications in the processing of skim-milk and whey. For example, in the field of whey processing, ion exchange is used in demineralization, lactose hydrolysis and in the pre-treatment of whey prior to protein recovery. In the case of skim-milk, applications include the manufacture of low Na milk and pre-acidification of skim-milk in casein manufacture. However, the ion exchange treatment of skim-milk to replace Ca ions with Na ions leads to far more fundamental changes with regard to the native protein conformation.

The effect of Ca removal from skim-milk is essentially to disrupt the native casein micelle structure into unassociated molecules of Na caseinate. Skim-milk modified in this way shows increased stability to alcohol and heat and increased functionality of the skim-milk protein in terms of water binding, emulsification and foaming capacity. The viscosity of Ca-reduced skim-milk is also substantially increased.

The improved functionality of Ca-reduced skim-milk makes the latter a potentially useful food ingredient in products where the above mentioned properties are important.