168 Chapter 7
Table 7.3. Typical composition of caseinates.
(Huffman and Harper 1999).
% Component Sodium
caseinateCalcium
caseinate
Protein 90.4 90.5
Moisture 4.6 4.6
Ash 3.8 3.7
Fat 1.1 1.1
Lactose 0.1 0.1
Calcium 0.03 1.3
Sodium 1.2 0.01
pH 6.8 6.8(typically 3.7%) because of the alkali used in
dissolution (Table 7.3 ). Sodium caseinate
contains 1.2% to 1.4% sodium, whereas
calcium caseinate contains 1.3% to 1.6%
calcium. Caseinates have a pH in the range
of 6.5 to 7.0.
Milk Protein Concentrates
Milk protein concentrates are concentrated
forms of milk proteins that contain both the
caseins and the whey proteins. The tradi-
tional method for producing milk protein
concentrates was to co - precipitate the casein
and whey proteins by heating skim milk, pre-
cipitating the complex between denatured
whey protein and casein with acid/calcium
chloride, and drying to obtain a powder. By
varying the processing conditions, milk
protein co - precipitates (80% to 90% protein)
with different amounts of calcium and func-
tional properties can be obtained (Vattula
et al. 1979 ). This traditional method has been
now been replaced by ultrafi ltration for con-
centration of milk in the production of milk
protein concentrates and isolates. Unlike the
traditional process for total milk protein co -
precipitates, in which the structure of the
milk proteins is destroyed, concentration by
ultrafi ltration does not signifi cantly change
the milk protein structure.
During ultrafi ltration, water, lactose, and
mineral salts are removed in the permeate
stream and protein is concentrated (Peri et al.
1973 , Thompson and deMan 1975). The
retentate is enriched in protein but depleted
in lactose and soluble milk salts, and the milk
minerals associated with the casein micelle
remain. By using ultrafi ltration alone, milk
protein concentrates of up to 65% protein can
be obtained. For production of milk protein
concentrate powder with more than 65%
protein, diafi ltration is required. By adding
water in the fi ltration process, the lactose
and soluble milk salts can be further washed
out, leading to an increased protein content
of the retentate and therefore a higher protein
powder (Getler et al. 1997 ).Milk Protein Concentrates —
Manufacture and Composition
Manufacture of Milk
Protein Concentrates
The basic process for manufacture of skim
milk concentrates is given in Figure 7.3.
Typically, skim milk is pasteurized and
ultrafi ltered/diafi ltered at the normal pH
of milk. This process removes water and
dissolved solids (i.e., lactose and mineral
salts that are soluble in the serum phase of
milk). The ultrafi ltered retentate contains
the total milk protein with the same ratio
of casein : whey protein. The caseins in the
retentate that are isolated using this process
are in micellar form, their natural state in
milk.
Skim milk is typically concentrated fi ve -
to six - fold, which concentrates the protein
from 3.5% in skim milk to approximately
19% in the retentate, resulting in a powder
with 70% to 80% protein on drying (Zwijgers
1992). The protein content of the retentate is
further increased by diafi ltration for produc-
tion of milk protein isolate powders with
higher protein content (approximately 90%
protein in dry matter).
The ultrafi ltration can be carried out using
a cold (e.g., 10 ° C; 50 ° F) or hot (e.g., 50 ° C;