Ion exchange is used commercially in such processes as water softening, chemical purification, separation of ionic from non-ionic forms and analytical applications. Van Kreveld & van Minnen (1955) reported a method for the determination of Ca2+ and Mg2+ activity in milk using an ion-exchange resin. From this early work, it was established that with suitable resins exchange of salts was possible in milk, permeate and whey. This included the exchange of Ca and Mg from micelles by using Na+ or K+. Cationic resins of the Zerolit 236 type have been used successfully in the production of Ca-reduced single cream (Anderson et al. 1976). Such treatment prior to UHT processing was shown to increase physical stability when it was used as a coffee whitener. There is evidence that reduction of Ca2+ would also reduce the deposit formation that may occur during storage of UHT milk. Thus there is a need to establish commercial techniques to produce Ca-adjusted milks that could then be used as raw materials for industrial applications or product development work.

The present study investigated the use of ion exchange to reduce Ca in milk with particular reference to understanding the exchange of salts in Ca-reduced milk and the changes to some of its physical properties.