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.