195 / 258
G
olay
&
M
oulin
:
J
ournal of
AOAC I
nternational
V
ol
.
99, N
o
.
1, 2016
211
chromatographic capillary column of 100 m long has been
developed for its use in various laboratories using different GC
equipment and different types of injectors. The response factors
of the equipment have been taken into account in the calculations
to provide quantitative fatty acids results. The method has
already been implemented in several laboratories, and their
performance has been regularly evaluated and monitored via
proficiency tests. The method was also published in a scientific
paper (1) before being proposed for the standardization process,
first with the International Organization for Standardization
(ISO)–International Dairy Federation (IDF) as a NewWork Item
proposal moved forward to an International Standard (2). In
view of the absence of an internationally recognized analytical
method for fatty acids in the selected SPIFAN matrixes, the
method proposed to ISO-IDF was identified as a good candidate
to meet AOAC
Standard Method Performance Requirement
(SMPR
®
) 2012.011 (3, 4) defined by the AOAC Stakeholder
Panel on Infant Formula and Adult Nutritionals (SPIFAN).
In the frame of the agreement between ISO and AOAC to
develop common standards (signed June 18, 2012), it was
decided to merge the two activities to avoid duplicate work.
To verify the method performance for SPIFAN-selected
matrixes, a single-laboratory validation (SLV) study was
performed on all samples (SPIFAN test kit of 12 samples).
After evaluation of the SLV data, an AOAC Expert Review
Panel (ERP) determined that the method met SMPR 2012.011
as approved by SPIFAN. The ERP granted the method
Official First Action status on October 2, 2012 (5) and SLV
results were then published separately (6). The method was
recommended to advance to multilaboratory collaborative
study for the evaluation of reproducibility (7).
Collaborative Study
Although more than 30 laboratories initially indicated their
potential interest for involvement in this study, some were
not considered principally due to their location, difficulties in
shipping dairy samples, and time or resource constrains. The
final enrollment of participating laboratories, which included
food manufacturers, food regulatory agencies, food research
institutes, and private laboratories, was decided after satisfactory
results were shown on the training sample (a milk powder used
also in the collaborative study), and satisfactory chromatographic
resolution between C18:1
cis
and
trans
isomers, which is
essential for the accurate determination of TFAs in dairy
products. The six samples selected by SPIFAN were shipped
to participants from Covance Laboratories (Madison, WI),
and the six other samples selected by ISO-IDF were shipped
to participants from Nestlé (Lausanne, Switzerland) are listed
in Table 1. Each participant recorded data on a single template
that contained sections for reporting all raw data and fatty acid
calculations and for including chromatograms and comments.
Method
The protocol was based on AOAC First Action Method
2012.13
for analyzing infant formula and adult/pediatric
nutritional products and on the ISO-IDF method for analyzing
dairy matrixes (i.e., cheese sample).
AOAC Official Method 2012.13
Determination of Labeled Fatty Acids Content in
Milk Products, Infant Formula (and Adult/Pediatric
Nutritional Formula)
Capillary Gas Chromatography
First Action 2012
Final Action 2014
ISO/IDF-AOAC Method
A. Scope
The method is applicable to the determination of all fatty
acids, including individual labeled fatty acids [i.e., linoleic
acid (LA), α-linoleic acid (ALA), arachidonic acid (ARA),
ecosapentaenoic acid (EPA), and docosahexaenoic acid
(DHA)] and/or group of fatty acids [i.e., trans fatty acids
(TFAs), saturated fatty acids (SFAs), nonounsaturated fatty
acids (MUFAs), polyunsaturated fatty acid (PUFAs), omega-3,
Table 1. Collaborative study samples and codes
Sample No.
a
Product
Fat, %
Sample A
MLT code
b
Sample B
MLT code
1
Full cream (milk powder)
26.27
GHXZ007
SJLO002
2
Full cream (liquid milk)
3.55
JSYB023
GPOQ091
3
Full cream
35.27
KLMQ050
SYKA045
4
Butter
82.93
DDHU078
UYBE089
5
Cheese (soft)
13.29
MJFR034
WHTF002
6
Infant formula (powder)
25.67
SZEC013
VCIN029
7
Adult nutritional (milk-protein powder)
17.44
LARU224
GLVC238
8
Infant formula (partially hydrolyzed soy powder)
26.01
LUJP087
ADVZ021
9
Infant formula (milk-based powder)
28.38
YKLP059
ZNPI092
10
Infant formula RTF (milk-based liquid)
3.57
MOPG098
SJLQ035
11
Adult nutritional RTF (high-protein liquid)
3.58
LHTK069
LKAU043
12
Adult nutritional RTF (high-fat liquid)
8.61
VFJL091
YATV077
a
Sample Nos. 1 to 6 were selected by ISO-IDF and shipped from Nestlé (Lausanne, Switzerland); Sample Nos. 7 to 12 were selected by SPIFAN and
shipped from Covance (Madison, WI). Analysis was performed on duplicate samples (A and B).
b
MLT = Multilaboratory testing.
195