Dairy Ingredients for Food Processing

186 Chapter 8

toward smaller ions. According to Hoppe and

Higgins (1992) , whey demineralization is

best carried out using strong acid cation

resins and medium to weak base anion resins.

Column systems are the most widely

employed. Cation and anion exchangers are

used either in mixed beds or in sequence. The

stirred tank reactor leads to high resin attri-

tion rates; most ion exchange resins are too

fragile to maintain their physical integrity

under these conditions.

As in the process described under ion

exchange chromatography for protein isola-

tion, the ion exchange process for deminer-

alization is carried out in four stages:

adsorption, washing, regeneration, and

rinsing. If sulfuric acid is used as a regener-

ant, care must be taken to avoid fouling the

system with calcium sulfate (Hoppe and

Higgins 1992 ). Precipitation is controlled by

using a progressive increase in acid strength

during regeneration.

using ion exchange chromatography pro-
cesses, i.e., stirred tank processes (e.g.,
VISTEC and BiPRO processes), packed -
column processes (e.g., Spherosil process),
and continuous counter - current adsorption
processes (e.g., ISEP contactor). Clogging
and channeling in the adsorption stage are
avoided in the stirred tank process. The dis-
advantage of the stirred tank process is that
it cannot remove all the protein from whey
and cannot equilibrate the bead with fresh
whey. Both of these objectives can be
achieved with packed - column processes.
However, the counter - current adsorption pro-
cesses are more effi cient than either stirred
tank or packed - column processes.

Ion Exchange (Demineralization)

In the ion exchange process of whey demin-
eralization, resins of lower porosity are pre-
ferred because they have a higher selectivity

Figure 8.6. Ion exchange process.

Whey feed

Cation

exchange

column

Anion

exchange

column

Deminerilized whey

Typical ions in whey

Resin-Na

Resin-Ca

Resin-Mg

Resin-K

Resin-H

Resin-CI

Resin-PO 4

Resin-SO 4

Resin-OH

Na+

Ca2+

Mg2+

K+

CI-

PO 4 3-

SO 4 2-