Oxidized fats in foods

Lipids and lipid oxidation with emphasis on cholesterol oxides in some Indian sweets available in London

Ghee (clarified butter oil), a major ingredient in Indian sweets, is an important source of saturated fatty acids, cholesterol and cholesterol oxidation products (COP) that are considered risk factors for atherosclerosis. The high frequency of atherosclerotic complications reported among the Indian immigrants in England prompted determination of lipids and lipid oxidation status of a ghee sample and 15 Indian sweets available in London supermarkets. The fatty acid profile of the samples shows saturated fats (about 73%), mainly composed of myristic, palmitic and stearic acids, except in two samples. There were large variations in thio-barbituric acid reacting substance values (19-260 microg/100 g) and total COP (1.4-51.2 microg/g lipids) among the sweet samples. Regular consumption of some of these sweets can be a source of considerable amounts of saturated fatty acids, cholesterol and COP in the diet and may contribute to atherosclerosis.

Changes in the fatty acid composition of M. longissimus dorsi of lamb during storage in a high-oxygen modified atmosphere at different levels of dietary vitamin E supplementation

The effect of vitamin E supplementation on fatty acid composition during storage of lamb meat packed in a high-oxygen modified atmosphere was studied. Lambs were fed with diets supplemented with four levels of vitamin E (0, 250, 500, and 1000 mg acetate-alpha-tocopherol/kg feed). Slices of M. longissimus dorsi were packed in a high-oxygen modified atmosphere (70% O2:30% CO2) and stored at 2 +/- 1 degrees C in the dark for 14, 21, and 28 days. The nonsupplemented group (E0) showed an increase in saturated fatty acids (SFA) and monounsaturated fatty acids and a reduction in polyunsaturated fatty acids (PUFA) in total fatty acids. The proportion of SFA and PUFA was unchanged in the supplemented groups (E250, E500, and E1000). The supplementation with 250 mg acetate-alpha-tocopherol/kg feed prevented the oxidation of PUFA in the total lipids and in the polar lipids fraction, while 500 mg acetate-alpha-tocopherol/kg feed was necessary to prevent the oxidation of PUFA in free fatty acids. Supplementing vitamin E not only inhibited lipid oxidation but also maintained nutritional value [essential fatty acids, linoleic acid (C18:2n-6) and linolenic acid (C18:3n-3), and beneficial fatty acids, eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3)] throughout the storage period.

Quantitative determination of epoxy acids, keto acids and hydroxy acids formed in fats and oils at frying temperatures

A method based on derivatization to fatty acid methyl esters and GC is proposed for the quantitative analysis of hydroxy acids, keto acids and epoxy acids in fats and oils. Isolation of the analytes by solid-phase extraction is proposed to prevent analytical interferences caused by non-altered fatty acids naturally occurring in oils. In addition, hydrogenation is required before the GC analysis to improve repeatability. The analytical method was applied to thermoxidized samples of high linoleic sunflower oil, high oleic sunflower oil and high palmitic sunflower oil. Results showed total levels of these compounds in the order of mg/g of oil in samples with contents of polar compounds ranging from 6.7 to 25.7%. The compounds analyzed constituted major fractions of the oxidized fatty acids.

Changes and Effects of Dietary Oxidized Lipids in the Gastrointestinal Tract

This paper is focused on the present state-of-the art of modifications and effects of dietary oxidized lipids during their transit along the gastrointestinal tract. A survey of the literature reporting changes and effects of oxidized lipids before absorption, first in the stomach and then during enzymatic lipolysis in the small intestine, are addressed. Also, the fate of non-absorbed compounds and their potential implications at the colorectal level are discussed. Among the results found, it is shown that acidic gastric conditions and the influence of other dietary components may lead to either further oxidation or antioxidative effects in the stomach. Also, changes in oxidized functions, especially of hydroperoxy and epoxy groups, seem likely to occur. Enzymatic hydrolysis by pancreatic lipase is not effective for triacylglycerol polymers, and hence they can be found as non-absorbed oxidized lipids in the large intestine. Interactions of oxidized lipids with cholesterol absorption in the small intestine and with microflora metabolism have been also observed.

Protection of lipids from oxidation by epicatechin, trans-resveratrol, and gallic and caffeic acids in intestinal model systems

Consumption of polyphenols is associated with health promotion through diet, although many are poorly absorbed in animals and humans alike. Lipid peroxides may reach the intestine and initiate deleterious oxidation. Here we measured inhibition of the oxidation of linoleic acid (LA) in authentic fluid from rat small intestine (RIF) by two dietary polyphenols, a flavonoid, epicatechin (EC), and a stilbene, resveratrol (RV), and by gallic (GA) and caffeic (CA) acids, and their partition coefficients. Both polyphenols inhibited 80%, and CA inhibited 65%, of the production of hexanal. GA was the weakest antioxidant in this assay. Interestingly, measuring peroxides production in RIF showed that only epicatechin inhibited the first stage of oxidation. The oxidizing agent, the antioxidant comound, the solution pH and lipophilicity are known to affect the total antioxidative activity. We suggest that the mechanism of this activity changes in accord with the environment: i.e., RV may act as a free radial scavenger, but here, in protecting lipids in intestinal fluid from oxidation, it acts as a hydrogen atom donor. Since the concentration of phenolics is much higher in the intestinal fluid than is ever achieved in plasma or other body tissues, it is suggested that their antioxidant activity could be exerted in the gastrointestinal tract (GIT), breaking the propagation of lipid peroxides oxidation and production of toxic compounds.

Postprandial lipid oxidation and cardiovascular disease risk

A mild pro-oxidative state accompanies meal ingestion, which results in an increase in biomarkers of inflammation, adhesion, and endothelial dysfunction, all of which are factors in the development of cardiovascular disease. Both fat and carbohydrate can cause the effect, which is additive and exacerbated by diabetes. The presence of lipid, glucose, and cholesterol oxidation products of dietary or endogenous origin may contribute to postprandial oxidative stress. However, the generation of excess superoxide due to abundant energy substrate after the meal may be a predominate factor resulting in oxidative stress and a decrease in nitric oxide, which is important to endothelial function. Remediation of postprandial oxidative stress through direct reduction of superoxide generation and simultaneous consumption of antioxidants with each meal should be a focus of future research.

Formation and evolution of monoepoxy fatty acids in thermoxidized olive and sunflower oils and quantitation in used frying oils from restaurants and fried-food outlets

The formation and evolution of monoepoxy fatty acids, arising from oleic and linoleic acids, were investigated in olive oil and conventional sunflower oil, representatives of monounsaturated and polyunsaturated oils, respectively, during thermoxidation at 180 degrees C for 5, 10, and 15 h. Six monoepoxy fatty acids, cis-9,10- and trans-9,10-epoxystearate, arising from oleic acid, and cis-9,10-, trans-9,10-, cis-12,13-, and trans-12,13-epoxyoleate, arising from linoleic acid, were analyzed by gas chromatography after oil derivatization to fatty acid methyl esters. Considerable amounts, ranging from 4.29 to 14.24 mg/g of oil in olive oil and from 5.10 to 9.44 mg/g of oil in sunflower oil, were found after the heating periods assayed. Results showed that the monoepoxides quantitated constituted a major group among the oxidized fatty acid monomers formed at high temperature. For similar levels of degradation, higher contents of the monoepoxides were found in olive oil than in sunflower oil. Ten used frying oils from restaurants and fried-food outlets in Spain were analyzed to determine the contents of the monoepoxides in real frying oil samples. Levels ranged from 3.37 to 14.42 mg/g of oil. Results show that, for similar degradation levels, the monoepoxides were more abundant in the monounsaturated oils than in the polyunsaturated oils.

Rapid quantitative assessment of the adulteration of virgin olive oils with hazelnut oils using Raman spectroscopy and chemometrics

The authentication of extra virgin olive oil and its adulteration with lower-priced oils are serious problems in the olive oil industry. In addition to the obvious effect on producer profits, adulteration can also cause severe health and safety problems. A number of techniques, including chromatographic and spectroscopic methods, have recently been employed to assess the purity of olive oils. In this study Raman spectroscopy together with multivariate and evolutionary computational-based methods have been employed to assess the ability of Raman spectroscopy to discriminate between chemically very closely related oils. Additionally, the levels of hazelnut oils used to adulterate extra virgin olive oil were successfully quantified using partial least squares and genetic programming.