Casein, Caseinates, and Milk Protein Concentrates 169outlet temperatures of the dryer can be detri-
mental to the powder properties. For example,
increasing the outlet temperature of a pilot -
scale spray dryer equipped with a two - fl uid
nozzle from 65 ° C to 90 ° C (149 ° F to 194 ° F)
decreased solubility (pH 7.0) and rate of re -
hydration of milk protein concentrates with
70% protein (MPC 70) (de Castro and Harper
2001 ). Drying milk protein concentrates
(MPC 70) using higher inlet temperatures
(i.e., increasing temperature from 200 ° C
to 250 ° C and 300 ° C; 392 ° F to 482 ° F and
572 ° F) in a pilot - scale spray dryer reduced
the rate of rehydration of the powder (de
Castro and Harper 2003 ).
For commercial operations, a tall form
dryer coupled to an external fl uidized bed for
cooling the powder is desirable to obtain a
high - quality milk protein concentrate powder
(Getler et al. 1997 ).122 ° F) process. The level of concentration of
the retentate obtained depends on whether
the cold or hot process is used and the type
of membrane or combination of membranes
employed (i.e., spiral wound, plate and
frame). Using the cold process, milks can be
concentrated to 20% to 24% total solids.
More of the water is taken out in an evapora-
tor (normally a falling fi lm tubular evapora-
tor) to obtain a higher total solids concentrate,
typically with 32% to 35% total solids, prior
to spray drying. When the hot process is
used, concentrates of 28% to 33% total solids
can be achieved and the evaporation step
may be omitted (Getler et al. 1997 ).
Various spray dryers may be used for
drying. The operating conditions of the dryer,
such as the inlet and outlet temperatures,
affect the characteristics of the milk protein
concentrate powders. Increasing the inlet or
Figure 7.3. Process for manufacture of milk protein concentrate (MPC) powder.
PasteurizationUltrafiltering /
DiafilteringRetentateEvaporating
(Optional)DryingSpray-dried MPCWater
Lactose
Mineral saltsWaterSkim milk