Acceleration of Lipid Oxidation by Volatile Products of Hydroperoxide Decomposition (original) (raw)
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Roles of peroxides and unsaturation in spontaneous heating of linseed oil
Fire Safety Journal, 2013
This contribution aims to elucidate the chemical aspects of the autoxidation of linseed oil that may lead to self-heating and fires, especially for linseed oil doped with salts of transition metals, in the presence of an additional fuel, such as cotton. We examine the formation of peroxides, which function as important intermediates in the autoxidation reaction. In particular, we describe the relationship between the formation of peroxides and changes in the degree of unsaturation, together with other structural and compositional modifications occurring in the molecules of unsaturated fatty acid esters. Transition metal salt catalysts were found to decompose peroxides which had built up during the autoxidation reaction of linseed oil, thereby increasing the number of reactive radicals and resulting in higher product yields. Higher temperatures increased the rate of peroxide decomposition. The overall activation energy for peroxide formation corresponds to 71 7 1 kJ mol À 1 . FTIR analysis of oil film demonstrated the progressive decrease in the concentration of cis non-conjugated double bonds, formation of trans conjugated double bonds, appearance of hydroxyl groups and the broadening of the carbonyl peak. The overall rate of disappearance of double bonds follows first order kinetics with a rate constant of 0.030 7 0.007 h À 1 .
Journal of the science of food and agriculture, 2018
The oxidative deterioration of vegetable oils is commonly measured by the peroxide value, thereby not considering the contribution of individual lipid hydroperoxide isomers, which might have different bioactive effects. Thus, the formation of 9- and 13-hydroperoxy octadecadienoic acid (9-HpODE and 13- HpODE), was quantified after short-term heating and conditions representative of long-term domestic storage in samples of linoleic acid, canola, sunflower and soybean oil, by means of stable isotope dilution analysis-liquid chromatography-mass spectroscopy. Although heating of pure linoleic acid at 180 °C for 30 min led to an almost complete loss of 9-HpODE and 13-HpODE, heating of canola, sunflower and soybean oil resulted in the formation of 5.74 ± 3.32, 2.00 ± 1.09, 16.0 ± 2.44 mmol L 13-HpODE and 13.8 ± 8.21, 10.0 ± 6.74 and 45.2 ± 6.23 mmol L 9-HpODE. An almost equimolar distribution of the 9- and 13-HpODE was obtained during household-representative storage conditions after 56 da...
Lipid Oxidation. Part. 1. Effect of Free Carboxyl Group on the Decomposition of Lipid Hydroperoxide
Food / Nahrung, 1976
Hydroperoxido butyl oleate was decomposed by heating in excess palmitic acid at Go-120 "C. The decomposition followed the kinetics of a first order reaction with formation of both monomeric and oligomeric secondary products. The proportions of oligomers slightly increased with increasing reaction temperature and decreased with increasing concentration of hydroperoxide. The activation energy was 70.4 kJ/mol f 4.7 kJ/mol. The detomposition of hydroperoxides proceeded partially by monomolecular cleavage, partially by formation of esters with palmitic acid.
Mechanism of Formation of Volatile Organic Compounds from Oxidation of Linseed Oil
Industrial & Engineering Chemistry Research, 2012
The pathways of volatile organic compound (VOC) formation have been investigated through a computational study, employing the Gaussian 03 suite of programs. We optimized geometries and zero-point vibrational energies (ZPVEs) at the B3LYP/6-31G(d) level of theory and improved electronic energies by conducting single-point energy calculations using the large 6-311++G(3df,3pd) basis set. To describe the predominant mechanism of the linseed oil oxidation, the following sequence is proposed: hydrogen abstraction of unsaturated fatty compounds as the initiation reaction followed by the reaction of allylictype radicals with molecular oxygen to form peroxyl radicals and finally intramolecular rearrangement through four-and fivemembered rings. Quantum calculations identified low-energy pathways following cyclization resulting in the formation of major products observed, especially aldehydes and ketones. The overall energy changes taking place through the four-and fivemembered rings were found to be 78 and 93 kJ mol −1 exothermic, respectively. Metal catalysts decompose hydroperoxides based on the Fenton-like mechanism into alkoxyl and peroxyl radicals.
Repeatedly Heated Vegetable Oils and Lipid Peroxidation
Vegetable oils such as palm and soy oils are commonly used in frying. During frying, the oils undergo thermal chemical changes producing various oxidative products. The study was conducted to determine the effects of repeatedly heating on the quality of palm and soy oils, as well as the effect of these thermoxidized oils on plasma lipid peroxidation in rats. A kilogramme of sweet potato was fried in 2.5 L of palm or soy oil at 180°C for 10 minutes. The process was repeated four times to obtain five times heated oils. Later, respectively the fresh and heated oils (once and five times heated palm and soy oils) were incorporated into rat diet (15%) together with or without 2% cholesterol. Six groups of male Sprague Dawley rats were fed diets fortified with fresh or heated oils without addition of cholesterol respectively. While another six groups of female Sprague Dawley ovariectomized rats were respectively fed with fresh or heated oil diets added with cholesterol. The treatment duration was 4 months. The peroxide values were increased significantly in both heated oils. It was significantly higher in soy oil than palm oil. Comparatively, the fatty acid composition of palm oil after being heated was more stable than heated soy oil. However, the percentage of polyunsaturated fatty acids decreased as the soy oil was heated few times. Tocopherols and tocotrienols contents in both palm and soy oil were decreased with increased frequency of heating. Plasma lipid peroxidation was increased in rats that were fed diets containing heated palm and soy oils. In conclusion, repeated heating increased peroxide value, reduced vitamin E concentration and altered their fatty acid composition in the vegetables oils. Consumption of diet containing heated vegetable oils could be detrimental to health due to the presence of oxidative products in the heated oil.
Low temperature oxidation of linseed oil: a review
Fire Science Reviews, 2012
This review analyses and summarises the previous investigations on the oxidation of linseed oil and the self-heating of cotton and other materials impregnated with the oil. It discusses the composition and chemical structure of linseed oil, including its drying properties. The review describes several experimental methods used to test the propensity of the oil to induce spontaneous heating and ignition of lignocellulosic materials soaked with the oil. It covers the thermal ignition of the lignocellulosic substrates impregnated with the oil and it critically evaluates the analytical methods applied to investigate the oxidation reactions of linseed oil. Initiation of radical chains by singlet oxygen ( 1 Δ g ), and their propagation underpin the mechanism of oxidation of linseed oil, leading to the self-heating and formation of volatile organic species and higher molecular weight compounds. The review also discusses the role of metal complexes of cobalt, iron and manganese in catalysing the oxidative drying of linseed oil, summarising some kinetic parameters such as the rate constants of the peroxidation reactions. With respect to fire safety, the classical theory of self-ignition does not account for radical and catalytic reactions and appears to offer limited insights into the autoignition of lignocellulosic materials soaked with linseed oil. New theoretical and numerical treatments of oxidation of such materials need to be developed. The self-ignition induced by linseed oil is predicated on the presence of both a metal catalyst and a lignocellulosic substrate, and the absence of any prior thermal treatment of the oil, which destroys both peroxy radicals and singlet O 2 sensitisers. An overview of peroxyl chemistry included in the article will be useful to those working in areas of fire science, paint drying, indoor air quality, biofuels and lipid oxidation.
Journal of Animal Science, 2014
The objective of this experiment was to evaluate peroxidation in 4 lipids, each with 3 levels of peroxidation. Lipid sources were corn oil (CN), canola oil (CA), poultry fat, and tallow. Peroxidation levels were original lipids (OL), slow-oxidized lipids (SO), and rapid-oxidized lipids (RO). To produce peroxidized lipids, OL were either heated at 95°C for 72 h to produce SO or heated at 185°C for 7 h to produce RO. Five indicative measurements (peroxide value [PV], p-anisidine value [AnV], thiobarbituric acid reactive substances [TBARS] concentration, hexanal concentration, 4-hydroxynonenal [HNE] concentration, and 2,4-decadienal [DDE]) and 2 predictive tests (active oxygen method [AOM] stability and oxidative stability index [OSI]
European Food Research and Technology, 2002
Interactions between α-tocopherol (α-TOH) and lipid hydroperoxides (LOOH) during the oxidation of methyl linoleate were studied in a model system using the response surface methodology statistical technique. When no α-TOH is present, LOOH had only slight pro-oxidative effects on the oxidation of methyl linoleate. High initial levels of α-TOH caused increased consumption and loss of efficiency for this antioxidant. The time for α-TOH consumption and the induction period for the oxidation of methyl linoleate were increased by increasing initial α-TOH concentration but were decreased by increasing initial LOOH as well as by interactions between LOOH and α-TOH. Interactions among LOOH molecules and between LOOH and α-TOH molecules had negative effects on the stability of α-TOH and the rate of oxidation of methyl linoleate as evidenced by the rate of α-TOH consumption, the rate of LOOH formation, the ratio of cis,trans/trans,trans LOOH and the rates of formation of hydroxy and ketodiene compounds during the induction period. Thus, the efficiency of α-TOH as an antioxidant is determined by, as yet unknown, interactions involving α-TOH and/or LOOH which are both present during the induction period.