Heated Corn Oil Research Articles

EFFECT OF FRESH AND HEATED CORN OIL FEEDING ON LIPID METABOLISM IN RATS

EFFECT OF FRESH AND HEATED CORN OIL FEEDING ON LIPID METABOLISM IN RATS

The effect of glycine in the production of toxic volatile aldehydes from heated corn oil

AbstractThe fatty aldehydes generated from heated corn oil and from several corn oil/glycine mixtures were collected by a dynamic headspace sampling method and subsequently reacted with cysteamine to yield corresponding thiazolidines. Derivatized aldehydes were analyzed by a capillary gas chromatograph with flame photometric detector. Six fatty aldehydes, including formaldehyde and acetaldehyde, decreased in concentration in relation to increasing amounts of glycine in the oil.

Headspace volatile compounds formed from heated corn oil and corn oil with glycine

The headspace volatiles produced from heated corn oil or from corn oil with glycine were isolated and identified to investigate the influence of nitrogen-containing constituents in the formation of aroma chemicals associated with cooked lipid-rich foods.

COMPARATIVE SIZE DISTRIBUTION AND FILTER PENETRATION MEASUREMENTS OF DOP AND CORN OIL AEROSOLS

ABSTRACT The use of corn oil as an alternative aerosol base in instruments for testing respirators and filters has been recommended by NIOSH as a safe substitute to Di-ethylhexyl phthal-ate (DOP) which is thought to be a potential biological co-carcinogen. Experimental measurements of the thermophysical properties related to aerosol size distribution and filter penetration have been conducted using photometry, inertial impactors, and laser spectrometry. Aerosols were generated using a pneumatic generator that combined the concepts of the Laskin nozzle and Wright nebulizer systems under various conditions of pressure, temperature and relative humidity and were evaluated for particle size distribution and filter penetration. Experiments demonstrated that heating corn oil from 20°C to 40°C has a minimal effect on size distribution and mass whereas DOP showed a greater sensitivity to temperature with respect to the same properties. These evaluations also demonstrated that corn oil produced a stable, smaller, and more consistent aerodynamic size distribution than DOP at the comparative experimental conditions. Comparable filter penetration characteristics obtained by experimental observations strongly show that corn oil aerosols are justified as an alternative aerosol for DOP. Enhanced performance coupled with safety considerations suggest that corn oil is an acceptable substitute for DOP especially in those applications of testing human subjects such as quantitative fit testing.

Biological observations from feeding heated corn oil and heated peanut oil to rats.

Five groups of male weanling rats were provided purified diets containing 15% by weight of either fresh or laboratory-heated corn oil (FCO, HCO) or fresh, laboratory-heated, or commercial pressure deep-fry peanut oil (FPO, HPO, PPO). Total weight gain, feed consumption, and feed efficiency were consistently greater for the FCO, FPO, and PPO groups. Although relative heart weights were unaffected, the HCO and HPO produced elevated liver and kidney weights. The dietary fats had no effect on the hematological status of the animals or the proportions of cells comprising the total leukocytes of the blood. Physical, chemical, and microscopic evaluation of the urine detected no pathologic conditions. Rats fed diets containing HCO or HPO demonstrated toxicity of thermally oxidized fats by the appearance of diarrhea, dermatitis, seborrhea, and hair loss. Histological examinations revealed injury of the thymus by all fat samples except the FCO; the liver was damaged by the HCO, HPO, and PPO, and the testes and epididymides by HPO and PPO. In the latter case there was complete cessation of spermatogenesis.

Cytotoxicity of thermally oxidized fats.

The effects of oxidized fat components (free fatty acids from the distillable nonurea adductable fraction) isolated from heated corn oil or heated olive oil on the morphology and growth of heart cells in primary culture were investigated. The free fatty acid fractions isolated from the fresh fats served as controls. Different concentrations of the fat fractions (20, 60, and 100 micrograms/ml) were added to the medium in the form of an emulsion with bovine serum albumin (Fraction V, poor in unesterified fatty acids). In the cell cultures treated with heated fats, intracellular lipid accumulation, increased cytoplasmic vacuolization, mitotic aberrations, pyknotic cells, and decreased mitosis were observed and were more pronounced in the case of the heated olive oil. These cytotoxic effects increased with higher concentrations of heated fats in the medium. The fresh fats also produced intracellular lipid accumulation, reductions in mitosis, and changes in the nucleus and cytoplasm, at the higher levels. These effects were greater in fresh olive oil-treated cultures. These observations indicate that oxidized fat components interfere physically or biochemically with normal cell functions resulting in pathological changes.

A gas chromatographic method for the assessment of used frying oils: Comparison with other methods

AbstractThe application of a simple and rapid method, based on gas chromatographic measurement of dimer triglycerides, is proposed for evaluation of the quality of used frying oils. The technique involves complete conversion of the oil to its methyl esters followed by analysis on a short column packed with 3% JXR. Parameters are adjusted to provide a pattern in which the dimeric esters emerge as a doublet peak with a retention time of ca. 3 min, whereas all other monomeric esters elute with the solvent peak. The relative heights of the two components of the doublet peak appear to reverse as the frying time is increased. The test correlated well with changes in dielectric constant measurements, as well as with “altered triglycerides” in continuously heated corn oil.

Effects of vitamin E and ascorbyl palmitate on cultured myocardial cells exposed to oxidized fats.

Primary cultures of rat heart cells were used as a model system to study the influence of two antioxidants, vitamin E and ascorbyl palmitate, on biological effects of thermally oxidized fat. The free fatty acid fraction of the distillable non-urea-adductable fraction of heated corn oil (HCO) was used as the test lipid; the free fatty acid fraction of fresh corn oil was the control. HCO (100 microgram/ml medium) depressed the mitotic index, induced excessive lipid accumulation, and increased the number of pyknotic nuclei in the cells. Addition of extra vitamin E (10 microgram/ml medium) reduced the toxicity of HCO by counteracting these changes. In comparison, ascorbyl palmitate (10 microgram/ml medium) in the presence of HCO was beneficial in that it produced only a slight increase in the mitotic index. HCO treatment also resulted in reduced levels of linoleic and arachidonic acids in the phospholipid fractions of the cells, and addition of vitamin E or ascorbyl palmitate increased the level of arachidonic acid. The triacylglycerol fraction of HCO-treated cells showed markedly reduced linoleic acid and increased arachidonic acid. These changes were unaffected by the antioxidant treatments. Vitamin E counteracted the adverse effects of HCO treatment on the rat heart cells. Ascorbyl palmitate only was as efficient as vitamin E in elevating the concentration of arachidonic acid at the membrane level in the presence of HCO.

Uptake and utilization of 1-14C palmitic acid by heart cells treated with fresh or thermally oxidized fats.

The effects of fractions isolated from thermally oxidized corn oil or olive oil on the metabolic activity of heart endothelial and muscle cells were studied. Rat heart cells in culture, exposed to thermally oxidized fat components, took up more exogenous 1-14C-palmitic acid and incorporated more of it into the cell triacylglycerol fraction than when the cells were treated with fresh fats. Particularly with the heated corn oil compared to fresh corn oil, much less of the radioactivity from the labeled palmitic acid was deposited in the phospholipid fraction. Also, with heated corn oil when the incubation period was extended beyond 12 hr, there was a decline in the radioactivity retained in the triacylglycerol fraction of the heart muscle cells. When the fresh fats were compared for 14C-radioactivity incorporation into the heart cells, the olive oil gave much higher values, indicating a distinct difference in response to the proportion of fatty acids supplied.

The effect of the duration of cholesterol feeding on the development of sudanophilic lesions in the rabbit aorta

Polar coordinate mapping was used to determine the rate of growth of individual sudanophilic lesions on the aortic wall around several major branches of the aortae of cholesterol fed rabbits. Four groups, with 6–8-month old male albino white rabbits in each, were used in the study. One group served as a control and the remaining 3 were fed a diet of 2% cholesterol and 6% heated corn oil mixed with ground rabbit pellets for 4, 8, and 10 weeks each. Animals were sacrificed, the aortae removed, stained with Sudan III, pinned at in vivo dimensions, and mapped by the polar coordinate method. No sudanophilic lesions were observed in the control animals. In the experimental groups, the early lesions, except the coronaries, were almost entirely distal to the orifices, and maintained roughly the same contour while spreading around the orifice. The coronary lesions completely encircled the orifices as described previously. As lesions progressed, they became elevated and often granular, so that the lesions themselves may have affected flow profiles around the orifices. Lesions around adjacent orifices were fused in 48% of the cases after 10 weeks on the diet, as opposed to 2% after 4 weeks on the diet. More prolonged experiments were not possible with this diet as the animals developed jaundice and diarrhea. Hemodynamically, these results suggest that early sudanophilic lesions in cholesterol-fed rabbits develop on the aortic wall in areas of high shear stress.

Effect of heated fat upon metabolism of 1- 14 C-acetate in the rat.

AbstractGroups of rats were prefed for 18 weeks with fresh or heated corn oil (≈5% nonurea adduct) at 10, 20 and 30% protein levels and at 10% protein+2% cellulose; 1‐14C‐sodium acetate was injected intraperitonially into each animal and the radioactivity was measured in expelled CO2 and also in the lipid fractions of liver. In the groups of rats fed 10% protein, one‐half of the administered radioactivity was found 50 min after acetate injection into rats fed fresh oil, whereas 90 min were required to reach the same level in rats fed heated oil. The same trend was found in all the groups of rats receiving different protein levels. The conversion of acetate to CO2 was significantly higher at a 10% dietary protein level than at the 20 or 30%, but there appeared to be no significant difference in the conversions at the 20 and 30% protein levels. However addition of 2% cellulose to the 10% dietary protein level significantly increased the conversion of the acetate to CO2 in rats fed heated oil. The livers of animals receiving heated fat diets had a higher lipid content, mainly triglyceride. When the liver lipids from rats fed fresh corn oil were separated by argentation thin layer chromatography, the bulk of the radioactivity was found in the saturated fractions. Monoene, diene and triene fractions from the liver lipid of rats fed heated oil had almost twice the radioactivity of those from fresh oil, suggesting the preferential utilization of acetate in the synthesis of these unsaturated fatty acids.

The cis, cis-Linoleic Acid Content of Heated Oils

Lipoxidase was used to measure die cis-methylene-interrupted, polyenoic acids in heated corn oil, rapeseed oil and soybean oil. The loss of these polyenoic acids was small during the first 4 hours of heating at 180°C, but increased at 212°C and with longer heating times. The total proportion of such acids which disappeared was unrelated to the total amount originally present in the oil. Absorbance at 440mμ by the oils also increased with temperature and time of heating, except that soybean oil appeared the same at 180 and 212°C. The frying of 6 successive batches of potatoes in corn oil was associated with less than a 7% decrease of cis, cis-linoleic acid in this oil. Corn oil in “brownies” was more susceptible to thermal oxidation than in a cake containing more moisture and baked at a lower temperature. Generally, there was good retention of cis-methylene-interrupted, polyenoic acids under these moderate conditions of food processing.

Cholesterol vehicle in experimental atherosclerosis: Part 9. Comparison of heated corn oil and heated olive oil

Summary The atherogenic effects of diets containing cholesterol suspended in heated or unheated olive and corn oils were compared. The diet containing heated corn oil was more atherogenic than that containing unheated corn oil, confirming our previously published findings. The increased atherogenicity of the heated corn oil diet could be correlated with an increase in its free fatty acid content. The two olive oil diets were of comparable atherogenicity, and heating did not elevate the free fatty acid content of the olive oil. These findings further suggest that one of the factors affecting atherogenicity of heated fats is their free fatty acid content.

Cholesterol Vehicle in Experimental Atherosclerosis

Summary The atherogenic effects of diets containing cholesterol suspended in heated or unheated olive and corn oils were compared. The diet containing heated corn oil was more atherogenic than that containing unheated corn oil, confirming our previously published findings. The increased atherogenicity of the heated corn oil diet could be correlated with an increase in its free fatty acid content. The two olive oil diets were of comparable atherogenicity, and heating did not elevate the free fatty acid content of the olive oil. These findings further suggest that one of the factors affecting atherogenicity of heated fats is their free fatty acid content.

Effect of heat on triglycerides of corn oil

AbstractResults of a study on the effect of heating corn oil in air to a 200C temp are reported. Heated oil was separated on a silicic acid column into 8 fractions. The first four fractions, constituting about 62% original oil, were found to be unchanged triglycerides. The remaining 4 fractions constituted polymeric and degraded products of high molecular wt. Percentage losses from the respective positions in the oleo‐ and linoleoglyceride fractions suggest that fatty acids in primary positions are slightly more susceptible to heat than those in the 2‐position. Assuming a 1,3‐random 2‐random distribution, triglyceride fraction in the heated oil contained 6.7% trilinolein as compared to 17.7% in fresh oil. Evidence is presented which shows presence of branching in short chain unsaturated acids and of hydroxy acids in the saponified polymeric fractions.

Cholesterol vehicle in experimental atherosclerosis part IV. Influence of heated fat and fatty acids*

Rabbits maintained on diets containing cholesterol (2 %) dissolved in corn oil (6 %) by heating display more severe atheromata than do rabbits fed cholesterol suspended in corn oil. This effect is independent of the source of the corn oil. It is believed that the increased atherogenicity is due to the higher level of free fatty acids present in the heated corn oil. These acids arise from hydrolysis of the corn oil which occurs during heating. Feeding rabbits 2 % cholesterol suspended in 5.75 % corn oil to which 0.25 corn oil fatty acids have been added also leads to more severe atheromata than in the absence of the fatty acids. The same effect is observed when linoleic or stearic acids are substituted for the corn oil fatty acids. Suspension of cholesterol in corn oil which has been heated previously also yields a more atherognc diet. The mechanism by which fatty acids exert this effect is not known. Des lapins nourris avec un régime contenant 2 % de cholestérol dissous par chauffage dans de l'huile de mais (6 %) developpent un athérome plus sévère que des lapins nourris avec un régime contenant du cholestérol dispersé dans l'huile de maïs. Cette différence est indépendante de la provenance de l'huile. L'augmentation du pouvoir athérogène est attribuée au taux plus élevé d'acides gras libres dans l'huile chauffée. Ces acides proviennent de l'hydrolyse de l'huile au cours du chauffage. Des lapins nourris avec 2 % de cholestérol dispersés dans 5.75 % d'huile de maïs additionnée de 0.25 % d'acides gras provenant d'une huile de maïs développent eux aussi un athérome plus sévère que si on n'ajoute pas d'acides gras. Le même resultat est obtenu quand on substitue aux acides gras de l'huile de maïs, de l'acide linoléique ou stéarique. Une suspension de cholestérol dans dhuile de maïs préalablement chauffée fournit aussi un régime plus athérogène. Le mécanisme de faction des acides gras n'est pas connu. Kaninchen, deren Futter Cholesterin (2 %) enthielt, das in Maisöl (6 %) durch Erhitzen gelöst wurde, boten schwerere Atherome als Tiere, die Cholesterin erhielten das in Maisöl suspendiert war. Diese Wirkung war von der Herkunft des Maisöls unabhängig. Es wird angenommen, dass die gesteigerte atherogene Wirkung mit deco höheren Gehalt an freien Fettsäuren in dem erhitzten Maisöl zusammenhängt. Diese Säuren entstehen während der Erhitzung durch Hydrolyse. Verfüttert man 2 % Cholesterin, das in 5.75 % Maisöl suspendiert war and dem 0.25 % Maisölfettsäuren hinzugefügt wurden, so bekamen auch these Tiere schwerere Atherome als ohne die Zugabe der Fettsäuren. Wird das Cholesterin in vorher erhitztem Maisöl suspendiert, so wird die Kost gleichfalls stärker atherogen. Der Mechanismus dieser Fettsäurenwirkung ist nicht bekannt.

EFFECTS OF VARYING PROPORTIONS OF DIETARY RAPESEED OIL ON THE RAT

Rapeseed oil, corn oil, and mixtures of the two oils containing 5, 10, 20, 40, and 80% rapeseed oil were fed to weanling rats at levels of 10 and 20% by weight of the purified diet. A significant decrease in body weight gains and in food consumptions occurred with the two highest levels of rapeseed oil, that is, 16 and 20% by weight of the total diet. At the same levels there was an increased lipid excretion. Corn oil and rapeseed oil which had been heated to 200 °C. for 120 hours produced no changes in weight gains when fed at the 10% level, but exhibited some growth-retarding effects at the 20% level. At both levels heated corn oil and rapeseed oil increased the liver weight of male rats.

EFFECTS OF VARYING PROPORTIONS OF DIETARY RAPESEED OIL ON THE RAT

Rapeseed oil, corn oil, and mixtures of the two oils containing 5, 10, 20, 40, and 80% rapeseed oil were fed to weanling rats at levels of 10 and 20% by weight of the purified diet. A significant decrease in body weight gains and in food consumptions occurred with the two highest levels of rapeseed oil, that is, 16 and 20% by weight of the total diet. At the same levels there was an increased lipid excretion. Corn oil and rapeseed oil which had been heated to 200 °C. for 120 hours produced no changes in weight gains when fed at the 10% level, but exhibited some growth-retarding effects at the 20% level. At both levels heated corn oil and rapeseed oil increased the liver weight of male rats.