ISO/WD
12
© ISO 2013 – All rights reserved
This calculation can be only performed when the fat content is determined with an appropriate validated
extraction method. Do not use the declared fat value for the expression of fatty acids on finished products.
10.1.4 Sum of class or group of fatty acids in 100g product
Calculate the mass fraction of all fatty acids included in a group or in a class of fatty acids by simple addition of
individual fatty acids results, (expressed in gFA/100g product). (Annex A Table A.1);
10.1.5 Sum of class or group of fatty acids in 100g fat
Calculate the mass fraction of all fatty acids included in a group or in a class of fatty acids by simple addition of
individual fatty acids results (expressed in gFA/100g fat).
10.1.6 Performance of the
trans
esterification
Record the areas of the two internal standard peaks (methyl undecanoate and tritridecanoin) in the analyzed
samples.
The performance of
trans
esterification,
PT
expressed in %, is calculated on the recovery of the tritridecanoin as
second internal standard as follows:
100
13
11
)
(13
13
13
11
cm cA
TAG cS cR cA cm
Pt
(5)
where
C11
m
is the mass, in milligrams, of C-11:0 internal standard added to the solution;
C13
A
is the peak area of C-13:0 internal standard in the chromatogram;
C13
R
is the response factor of C13:0 relative to C11:0, calculated according 10.1.1;
C13
S
is the stoichiometric factor to convert C13:0 FAME into C13:0 TAG (Annex B Table B.1);
C11
A
is the peak area of C-11:0 internal standard in the chromatogram;
C13
m
:
is the mass Liquid milk and liquid formula
The performance of the transesterification indicated by the recovery value of tritridecanoin (C13:0 TAG) should be
equivalent to 100,0 % ± 2,0 %. When the performance of the transesterification is >102,0 % or <98,0 % the origin
of the problem could be the following:
Incomplete transesterification (i.e. reagent performance)
Partial degradation of internal standard(s), or problem with their purity
Matrix effect problem
NOTE: The analysis of a reference sample can help to determine if the problem is originated from reagents and/or chemicals
or analysed sample.
