Abstract
Fatty acid methyl esters (FAMEs) in commercial milk samples were analyzed by gas chromatography coupled with flame ionization detection. The saturated fatty acids (SFA) were the most abundant. The major SFA were palmitic acid (16:0), estearic acid (18:0), and myristic acid (14:0). Significant differences (P < 0.500) were found between the amounts of palmitic acid (276 ± 17 mg g-1 and 248 ± 20 mg g-1) and myristic acid (95 ± 5 mg g-1 and 85 ± 7 mg g-1) in samples. However, no difference was observed for estearic acid (113 ± 6 mg g-1 and 114 ± 11 mg g-1). The conjugated linoleic acid (CLA) isomer 18:2c9t11 was detected in the samples and quantified. However, the differences found between the samples analyzed were not significant (10.4 ± 0.7 mg g-1 and 9.9 ± 0.6 mg g-1). The analysis of a certified reference powder milk sample (RM-8435 NIST) gave good recoveries (> 80%), indicating that the method can efficiently determine fatty acids in milk and dairy products.
Highlights
The advancement of the chemical study of foods is in great part due to the development of gas chromatography (GC)
Some problems may rise from the esterification of fatty acids, a process necessary for their analysis by GC: incomplete conversion of lipids into Fatty acid methyl esters (FAMEs), alteration of the fatty acid composition during transesterification, the formation of artifacts that may be erroneously identified as fatty acids or overlap with methyl ester peaks in GC analysis, contamination and resulting damage to the chromatographic column due to traces of esterifying
Methyl esters with different carbon chains will respond differently, which requires the use of correction factors.[5, 6]
Summary
The advancement of the chemical study of foods is in great part due to the development of gas chromatography (GC). The advancements in gas-liquid chromatography had an impact on the study of fatty acids, contributing, among other things, to the detailed investigation of positional and geometric isomers with distinct biological. Vol 21, No 3, 2010 reagent, incomplete extraction of FAMEs, and the loss of very volatile short-chain FAMEs.[4] the search for methods that minimize such interferences is warranted. Flame ionization detection is the most convenient method to analyze food fatty acids by gas chromatography. The flame ionization detector response is differential, that is, the magnitude of the signal is proportional to the number of active carbons. Methyl esters with different carbon chains will respond differently, which requires the use of correction factors.[5, 6]
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