AOACSPIFANMethods-2017Awards

201

G olay & M oulin : J ournal of AOAC I nternational V ol . 99, N o . 1, 2016  217

Figure 2012.13D. Example of GC chromatogram of the SPIFAN matrix sample infant formula powder, milk-based. Monounsaturated fatty acids and PUFAs are indicated, counting from the terminal methyl carbon toward the carbonyl carbon (designated as n or ω).

C18:3 TFA .—The sum of trans isomers from C18:3 in deodorized vegetable oils (i.e., C18:3 trans - 9, cis -12, trans -15; C18:3 cis -9, cis -12, trans -15; C18:3 cis -9, trans -12, cis -15; and C18:3 trans -9, cis -12, cis -15). Total TFA .—Sum of C18:1 TFA, C18:2 TFA, and C18:3 TFA.

expressed in grams FA i using the following equation:

per 100 g product in the test sample by

m A Rf S FA A m o i i i ⋅ ⋅ ⋅ ⋅

⋅ ( ) 100

gFA g product / 100

=

i

o

G. Calculations

where m O

= mass in milligrams of C11:0 internal standard

added to the sample solution D ( j ); A i in the sample chromatogram; Rf i

= peak area of FAME i = response factor, calculated

( 1 ) Calculation of response factors. —Determine the area of the peaks attributable to each FAME present in the calibration standard mixture, D ( p ), and calculate Rf i , their respective response factors relative to the internal standard (C11:0):

according to G ( 1 ); S i

(FA) = stoichiometric factor to convert

FAME i = peak area of C11:0 internal standard in the sample chromatogram; and m = mass in milligrams of the test portion. Note : For powder samples, the result is expressed in grams FA i per 100 g product, which can be converted to reconstituted liquid product (i.e., 25 g powder dissolved in 200 g water). Note : In the case of fatty acids analysis carried out on fat extracted from foods, the mass of test portion m corresponds to fat and not to the finished product. Consequently, fatty acids results are expressed in grams fatty acids per 100 g fat, which can then be converted into grams fatty acids per 100 g product, with the fat extraction value determined with an appropriate validated extraction method. ( 3 ) Fatty acids expressed on the total fat. —Calculate the mass fraction of the individual components expressed in grams FA i per 100 g fat in the test sample by using the following equation: to FA i (Table 2012.13 ); A O

′ ⋅ ′ ′ ⋅ ′ m A m A i O O i

Rf

=

i

where m′ i

= mass fraction of FAME i

in the calibration standard

solution, D ( p ); A′ O

= peak area of C11:0 in the calibration

standard solution chromatogram; m′ O calibration standard solution, D ( p ); and A′ i

= mass of C11:0 in the

 = peak area of

FAME i in the calibration standard solution chromatogram. The variation between three injections is optimal when coefficients of variation are <2.5. Note : The response factors calculated for C18:2 n -6 cis could be applied for the quantification of C18:2 CLAs, and those calculated for C18:3 n -3 cis could be applied for C18:3 trans isomers. ( 2 ) Fatty acids expressed on the product. —Calculate the mass fraction of the individual fatty acid components (FA i ),

/ 100 gFA g product Fat i %

⋅

100

/ 100 gFA g fat

=

i