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Differences in Oxidation Kinetics Between Conjugated and Non‐Conjugated Methyl Linoleate
Author(s) -
Luna P.,
Fuente M. A.,
Salvador D.,
MárquezRuiz G.
Publication year - 2007
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-007-3113-x
Subject(s) - conjugated system , chemistry , kinetics , conjugated linoleic acid , monomer , linolenate , organic chemistry , chromatography , polymer , fatty acid , physics , quantum mechanics , linoleic acid
The oxidation kinetics of conjugated methyl linoleate was compared with that of non‐conjugated methyl linoleate under mild oxidation conditions (30 °C in the dark). Samples of methyl 9‐ cis ,11‐ trans ‐linoleate, methyl 10‐ trans ,12‐ cis linoleate and methyl 9‐ cis ,12‐ cis linoleate were assayed separately and in mixtures. For comparative purposes, methyl α‐linolenate and methyl oleate were also used. Two complementary analytical approaches were selected to monitor the progress of oxidation, (1) the traditional follow‐up of residual substrate by gas liquid chromatography, and (2) an analytical procedure by high‐performance size‐exclusion chromatography (HPSEC) for direct measurement of the oxidation compounds formed. The HPSEC method enabled us to quantitate oxidized monomers, dimers and polymers concomitantly in a rapid and direct analysis. Results showed that conjugated methyl linoleate samples oxidized later than their non‐conjugated counterparts, and showed a very different oxidation pattern. Thus, formation of oxidized monomers was negligible and the first and major compounds formed were polymerization products. Also, under the conditions used, non‐conjugated and conjugated methyl linoleate samples in 1:1 mixtures led to decreased oxidation rate of non‐conjugated methyl linoleate and increased oxidation rate of conjugated methyl linoleate. This study supports the view that oxidation kinetics of conjugated dienes differ substantially from that of methylene‐interrupted dienes.