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520
F
eng
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
100, N
o
.
2, 2017
Conclusions and Recommendations
The SDS-CGE method is capable of accurately determining
the ratio of whey to casein in infant formulas manufactured using
different whey ingredients. Because whey and casein proteins,
as groups, have distinct migration times, the measurements
will not miss individual proteins. As a consequence, absolute
quantification of individual or total proteins is not necessary.
It was recommended that the method be further validated
by conducting a multilaboratory study. This would generate
valuable method performance data, including RSD
R
, further
enhancing the potential of this method for use in a routine QC
environment.
Table 9. Measured results of whey protein as the area
percentage of caseins for different batches of SMP samples
from different suppliers by SDS-CGE and the calculated
area CF of whey proteins to caseins
Whey as percentage of casein (mass)
Literature (4, 5)
26.9
Whey as percentage of casein (area)
Lot No.
n
a
Avg.
SD
EY06
3
20.02
0.58
CY25
2
20.62
0.35
DY06
2
20.25
0.17
DY19
4
20.58
0.30
DY21
5
20.44
0.81
DY29
b
24
21.32
1.00
M023
2
18.84
0.09
M075
2
22.26
1.02
M208
2
21.40
1.16
MSK
1
22.27
SMP DN1
1
21.53
SMP DN2
1
21.34
SMP DN3
1
19.79
Avg.
c
20.81
SD
d
0.99
CV, %
4.78
CF
1.29
Process impact
e
1.11
Final CF
1.4
a
n
= Number of measurement.
b
Four different batches of capillaries with two different sets of reagent
kits on 12 different days.
c
Avg. = Average.
d
SD = Standard deviation.
e
Obtained by evaluating processed and finished infant formula product
(Table 10).
Table 10. Comparison of the area percentage of whey
protein between the times after compounding and after
spray-drying during the processing of formula trial samples
Area
CF
Whey
Casein Whey/casein
Before
processing
306543
257994
1.19
1.11
After
processing
337097
314112
1.07
Table 11. Measured whey protein content in 43 different
infant formulas made by both local and international
manufacturers
Product
Manufacturer
whey claim, %
a
Measured whey, %
% of claim
n
Avg.
SD
1
60
12
59.9
0.50
100
2
b
70
18
70.7
0.34
101
3
60–65 (62.5)
12
56.4
0.80
90
4
40
18
41.8
0.47
104
5
c
65
12
64.7
0.30
99
6
60
4
59.6
0.23
99
7
60
4
59.7
0.66
99
8
65
4
65.9
0.41
101
9
65
3
63.2
0.34
97
10
b
70
3
71.2
0.84
102
11
d
60
3
62.9
1.15
105
12
60
2
57.3
0.09
95
13
60
2
64.4
0.10
107
14
60
2
63.2
0.27
105
15
60
2
63.7
1.26
106
16
N/L
e
2
20.2
0.92
17
70
2
69.0
1.03
99
18
c
65
2
62.2
1.69
96
19
65
2
65.5
1.03
101
20
70
2
70.6
1.51
101
21
61
2
61.5
1.43
101
22
70
1
62.4
89
23
>60 (65)
1
67.5
Pass
f
24
70
1
70.2
100
25
70
1
65.0
93
26
60
1
67.3
112
27
60
1
62.9
105
28
60
1
59.3
99
29
62
1
64.9
105
30
60
1
62.4
104
31
61
1
64.4
106
32
60
1
64.0
107
33
60
1
60.5
100
34
70
1
70.0
100
35
N/L
1
42.1
36
60
1
57.4
96
37
60
1
58.9
98
38
64
1
66.4
104
39
60
1
62.7
105
40
60
1
60.0
100
41
60
1
60.7
101
L1
g
21
2
22.6
2.43
108
L2
g
21
2
22.5
1.71
107
a
Numbers in parentheses represent value considered.
b
CGMP-reduced sweet whey formula.
c
α-Lac-enriched formula.
d
LF-enriched formula.
e
N/L = Not labeled.
f
Conform to claim.
g
The claim of 21.2% comes from the value for SMP, not a real claim.
238