Submitted to: Journal of Chromatography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/1998
Publication Date: N/A
Interpretive Summary: When fats or oils are heated or stay on the shelf for a long time, they undergo chemical processes that can create undesirable odors or flavors. To know how to make fats more resistant to forming these odors or flavors, it is important to know what chemical compounds are produced by the reactions that take place in the fat or oil. Products formed when fats swere aged were identified. This information can be used by food companies to make fats and oils with greater stability during heating, longer shelf lives and better flavor.
Technical Abstract: Oxidation products from the autoxidation of three triacylglycerol (TAG) standards were analyzed using reversed-phase high performance liquid chromatography (RP-HPLC) coupled to a mass spectrometer (MS)via an atmospheric pressure chemical ionization (APCI) source. Triolein, trilinolein and trilinolenin were autoxidized in the dark at 50-60 deg C until the oxidation products represented approximately 30% of the starting material. These oxidation product mixtures were then analyzed using RP-HPLC/APCI-MS. Several classes of oxidation products were directly detected and identified. Mono-hydroperoxides were present in the largest amounts in the oxidation products mixtures. The hydroperoxides were found to provide several structurally useful fragments. For example, epoxide intermediates were formed that then underwent further fragmentation, and other fragments were formed from concerted loss of the hydroperoxide group to form a site of unsaturation. Fragments formed by intra-annular cleavage of epoxide intermediates allowed identification of several hydroperoxide isomers. Bis-hydroperoxides were observed that underwent similar fragmentation pathways. Mono- and di-epoxides were also formed by the autoxidation reaction. Two classes of epoxides were observed; those in which an epoxide formed next to a double bond, and those in which an epoxide formed away from a double bond. Two distinct fragmentation mechanisms were observed for the two different types of epoxides.