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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Figure 4 The C-18 region of the gas chromatogram of the fatty acid methyl esters of<br />

canola–palm–butter spread using an SP-2560 100 m � 0.25 mm fused silica capillary column.<br />

Peak identification: 12,14,16–18, t,t-NMID; 19, t9,t12; 20, c9,t13; <strong>and</strong> t8,c12; 21, tc,ct; 22,<br />

t8,c13?, <strong>and</strong> cc-MID; 23, c9,t12; 24, c8,c13?; 25, t9,c12; 26, t9,c15, <strong>and</strong> t10,c15?; 27, c9,c13?;<br />

28, c9,c12; 29, c9,c15. NMID, non-methylene-interrupted diene; MID, methylene-interrupted<br />

diene. (From Ref. 58.)<br />

silver ion thin-layer chromatography (AgNO 3-TLC) (see Sec. B below) followed by<br />

GC on a highly polar 100-m capillary column allowed the determination of the<br />

average content of total trans-C16:1 to be 0.15 � 0.04% from 39 test samples of<br />

human milk fat [63]. The C16:1 positional isomers trans �4, �5, �6/7, �8, �9, �10,<br />

�11, �12, �13, <strong>and</strong> �14 were reportedly quantified in 15 test samples. The mean<br />

relative contents were 2.6, 3.5, 7.6, 7.2, 24.7, 10.4, 10.1, 14.3, 8.4, <strong>and</strong> 11.3% (as a<br />

percentage of total trans-C16:1), respectively [63].<br />

Wilson et al. [64] reported an AgNO 3-TLC combined with capillary GC technique<br />

for the quantitative analysis of trans monoenes derived from partially hydrogenated<br />

fish oil containing trans isomers with C-20 <strong>and</strong> C-22 carbons. Fatty acid<br />

methyl esters were separated into saturates (R-f 0.79), trans monoenes (R-f 0.4), cis<br />

monoenes (R-f 0.27), dienes (R-f 0.10), <strong>and</strong> polyunsaturated fatty acids with three<br />

or more double bonds remaining at the origin. These authors reported that direct GC<br />

analysis underestimated the trans content of margarines by at least 30%. In this study,<br />

C-20 <strong>and</strong> C-22 trans monoenes were found in relatively large quantities averaging<br />

13.9% <strong>and</strong> 7.5%, respectively, in margarines [64].<br />

Using a combination of Ag-TLC <strong>and</strong> GC, the frequency distributions of the<br />

conjugated linoleic acid isomer c9t11-C18:2, <strong>and</strong> the isolated or nonconjugated fatty<br />

acids trans-C18:1, trans-C18:2, t11-C18:1 (vaccenic acid), t11c15-C18:2 (major<br />

mono-trans-C18:2), as well as of total trans fatty acids were reported [65] for more<br />

than 2000 test samples of European bovine milk fats. These were obtained under<br />

different than normal feeding conditions: barn feeding, pasture feeding, <strong>and</strong> feeding<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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