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F
eng
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
100, N
o
.
2, 2017
519
Figure 13. E-gram of infant formula 4 with CGMP-reduced sweet whey ingredient (70% whey claim).
Figure 14. E-gram of infant formula 5 with sweet whey ingredient (40% whey claim).
Table 8. Protein profile of bovine milk and calculated whey
protein as the mass percentage of casein (4, 5)
Protein
MW, kDa
Whole milk content
g/L (5)
%
a
S1-casein
23.69
10.0
30.3
a
S2-casein
25.31
2.6
7.9
b
-Casein
23.97
9.3
28.2
k
-Casein
21.30
3.3
10.0
g
-Casein
20.59
0.8
2.4
a
-Lac
14.19
1.2
3.6
BSA
67.41
0.4
1.2
Immunoglobulin
160.00
0.8
2.4
Peptone 5
12.43
0.5
1.5
Peptone 3
17.89
0.3
0.9
LF
78.06
0.1
0.3
Milk fat globule
membrane
0.4
1.2
b
-Lg
18.27
3.3
10.0
CGMP
9.15
Sum
33.0
100.0
Casein
26.0
78.8
Whey
7.0
21.2
Whey as percentage
of casein
26.9
26.9
ratio from the literature with the area percentage ratio obtained
with the SDS-CGE method. Based on the literature mass
percentage ratio (26.9%) and the experimental area percentage
ratio (20.8%), a CF of 1.29 should be applied to the integrated
signal of whey proteins.
To evaluate the impact of the infant formula manufacturing
process on the area CF of whey proteins to caseins, a whey
protein-dominant infant formula was manufactured. Two
samples were taken; one before processing and one after. The
test results are listed in Table 10 and indicate that processing
further increased this ratio 1.11-fold. Therefore, a final CF of
1.4 for whey protein-to-casein area for infant formulas was
chosen (Table 9).
Forty-three infant formulas manufactured by both Chinese
and international manufacturers with different whey ingredients,
including regular sweet whey, α-Lac-enriched whey, LF-added
whey, and casein glycomacropeptide (CGMP)-reduced whey,
were analyzed and compared with manufacturers’ claims
(Table 11). The results show that among the 41 samples with
manufacturers’ claims, measured whey content was in close
agreement with declared value: within 5% of the declared value
for 31 (76%) samples and within 10% for 37 (90%) samples.
Two infant formulas did not contain added whey protein; hence,
a factor of 1.29, not 1.4, should be used. Taking this into account,
39 (95%) samples were within 10% of the declared value.
237