Dairy Ingredients for Food Processing

Casein, Caseinates, and Milk Protein Concentrates 167

care should be taken to avoid holding the

solution at above 70 ° C (158 ° F) for extended

periods, because this can result in the devel-

opment of brown color. Care should be also

taken to keep the incorporation of air to a

minimum, because sodium caseinate solu-

tions form highly stable foams (Towler

1976 ).

After a total time in the caseinating reac-

tors, usually 30 to 60 minutes, the caseinate

solution is pumped through a fi nal tubular

heater (90 ° C to 95 ° C; 194 ° F to 203 ° F) to

reduce its viscosity prior to spray draying.

The sodium caseinate solution formed has a

very high viscosity and is normally atomized

into the spray dryer at 130 ° C (266 ° F) and at

low total solids (20% total solids). Drying

from low total solids (20% total solids) incurs

high costs. Hence, a number of approaches

have been used in an effort to reduce these

costs (Muller 1983 ), including use of roller

drying and manufacture of extruded and

granular caseinates. It should be noted that

commercial caseinate manufacturing plants

can differ. For example, alkali can be added

at different points in different plants.

Caseinates have similar composition,

which is close to that of dry acid casein.

However, they have a lower moisture content

(typically about 4%) and a higher ash content

Caseinate — Manufacture

and Composition

The manufacture of caseinate has been previ-
ously reviewed (Mulvihill 1992 , Southward
1985 ). A plant layout for the manufacture of
sodium caseinate can be found in Figure 7.2.
Fresh curd from the dewatering press is
minced to break up lumps and then slurried
in water at 23% to 25% total solids. This
slurry is passed through a colloid mill to
reduce the curd particle size and produce a
fi ne dispersion of casein curd particles in
water. The reduction in particle size, prior to
addition of alkali, is believed to reduce the
time for dissolution of the curd. The addition
of dilute alkali is carefully controlled to
achieve neutral pH.
The dissolving operation is performed in
the caseinating vats. These are high shear
vessels with high - speed pumping facilities
for recirculation, to ensure good mixing of
the viscous caseinate solution prior to drying.
The number of dissolving vats, typically
three to fi ve in a series, varies depending on
the throughput of the dryer. To reduce the
viscosity of the caseinate solution, jacketed
vats are used to quickly raise the temperature
of the casein with added alkali solution to
65 ° C to 75 ° C (149 ° F to 167 ° F). However,

Figure 7.2. Proposed plant for manufacture of sodium caseinate. Adapted from Southward (1985).

1

2 3

5

6

7

(^98)
Casein dewatering
Hot water
4 Dilute alkali

1. Casein mincer


2. Colloid mill


3. Curd-alkali mixer


4. Dilute alkali storage


5. Jacketed vat


6. pH recording and control


7. Heat exchanger


8. Balance tank


9. Viscosity control

Water

1

2 3

5

6

7

(^98)
Casein dewatering
Hot water
4 Dilute alkali

1. Casein mincer


2. Colloid mill


3. Curd-alkali mixer


4. Dilute alkali storage


5. Jacketed vat


6. pH recording and control


7. Heat exchanger


8. Balance tank


9. Viscosity control

Water