Dairy Ingredients for Food Processing

Whey-based Ingredients 187

anion membranes to form a cell pair. Stacks

can accommodate fi ve to 500 cell pairs. As

shown in Figure 8.7 , whey is fed to alternate

fl ow channels and the remaining channels,

which are fed with brine, act as receivers for

the ions being removed (Hoppe and Higgins

1992 ).

Whey should be concentrated to 20% to

30% solids prior to electrodialysis to make

the process energy effi cient (Kilara 2008 ).

The system can be run in either batch mode

or continuous mode depending on the degree

of demineralization required. However, it is

often accepted that 50% demineralization

(which can be achieved by continuous pro-

cessing) is commercially viable. At higher

levels of demineralization, the high tempera-

tures of the process (30 ° C to 40 ° C; 86 ° F to

104 ° F) and long times increase the chances

of microbial contamination of the product.

Membrane fouling is a signifi cant problem

in electrodialysis. Both mineral fouling

(calcium phosphate on the cation membrane)

and protein fouling (anion membrane) can

occur during processing. According to Kilara

(2008) , the replacement costs of membranes

According to Hoppe and Higgins (1992) ,
the following variables affect the process:

• The presence of agglomerates from cheese
  or casein manufacture may reduce the
  process effi ciency.


• The feed concentration reduces the volume
  to be processed without reducing the
  demineralization load.


• Operating temperatures of 10 ° C (50 ° F) are
  often employed to reduce both the micro-
  bial growth in the system and the losses of
  protein and lactose by resin adsorption.

Electrodialysis

In electrodialysis the ionic components of a
solution are transported through selective
membrane barriers under the infl uence of an
electrical potential. An electric fi eld is formed
between the anode (positively charged) and
the cathode (negatively charged). Ion -
selective membranes, made of similar mate-
rial to ion exchange resins and with pore
sizes of 10 to 20 Å , are stacked between the
anode and the cathode, alternating cation and

Figure 8.7. Electrodialysis process.

A

Na+ Na+ Na+

CI- CI- CI-

AAA

Diluted side

Anode

solution

Cathode

solution

Concentrated side

CCCC

+ _