Chemical reactions involved in deep-fat frying of foods: VIII. Characterization of nonvolatile decomposition products of triolein.

Abstract

AbstractTriolein was heated under simulated deep‐fat frying conditions at 185 C for 74 hr. The thermally oxidized triolein was converted into methyl esters and then fractionated by urea exclusion. The urea adduct‐forming ester (89.2%) was found to be methyl oleate unchanged by the frying treatment. The nonurea adduct‐forming esters (10.8%) were further fractionated by silicic acid column chromatography into nine fractions with molecular weights ranging from 304 to 742. Physical and chemical analyses of the fractions indicated that some of them contained oxygen atoms which could not be accounted for by ordinary functional group analyses. The polymers isolated were formed by both carbon‐to‐carbon and carbon‐to‐oxygen linkages. The nonpolar dimers were further purified by thin layer and gas chromatography. Structure elucidation revealed that they consisted of a noncyclic dimer and a noncyclic dimer containing a carbonyl group, each of which amounted to 1.36% of the triolein originally used. The polar polymers were studied by depolymerization and the analysis of the depolymerized products. It was estimated that the triolein used for simulated deep fat frying contained 1.1% trimers formed through carbon‐to‐carbon linkages, 1.9% dimers and trimers joined through carbon‐to‐carbon linkages, and 3.1% dimers and trimers joined through carbon‐to‐oxygen or carbon‐to‐carbon linkages in the same molecule and also dimers and trimers in which all the monomeric units were joined through carbon‐to‐oxygen linkages. The precise form of the oxygen linkages are not known. However, the fact that it is not cleavaged by HC1 and HI suggests ether linkages.