We previously proposed that oil heated with gluten was suitable for use as a safe oil for weightloss dieting. In the present paper, the properties of the oil were improved, and the weight-loss effect was compared with that of heated oil. Fresh oil was heated for 10 h at 180 with or without gluten and filtered using filter paper. A powdered diet (AIN93G; no fat) was mixed with 7 wt% of fresh oil (control) or filtrates of the heated oils described above, and the mixture was fed to male Wistar rats for 12 weeks. The gluten and heated oil groups showed no gross symptoms attributable to the experimental oils but had a slowed body weight increase; a significant difference was found in weight on and after 21 weeks of age as compared to rats consuming the control diet, and fecal excretion was increased as compared to the control group. Serum levels of triacylglycerol, phospholipids, cholesterol, and glucose of the gluten and heated oil groups were significantly lower than those of the control group. High aspartate aminotransferase (AST) levels occurred more frequently in the heated oil group than the gluten group. The number of rats with dark red patches on the surface of the liver, which are indicative of liver damage, was higher in the heated oil group. In conclusion, the weight-reducing effect of the oil heated with gluten was confirmed and improved by removing traces of heated gluten from the oil.
Heated frying oils with different chemical properties in terms of AV (acid value), POV (peroxide value), COV (carbonyl value), and contents of polar compounds (PC) and triacylglycerol (TG), as well as color and odor, were obtained. Male Wistar rats were fed ad libitum for 12 weeks a powdered diet (AIN93G; no fat) containing 7 wt% of fresh oil (control) or one of the frying oils described above. The rats were subjected to anthropometric measurements, hematological analyses, and observations of the liver and kidneys. All of the rats grew well, and no gross symptoms attributable to the experimental oils were observed. However, the rats fed a diet containing the heated oil developed apparent liver damage to different degrees regardless of the chemical properties of the ingested oils. Thus, it was suggested that the chemical properties evaluated here had little to do with the cytotoxicity of heated oil, although the properties express quality of oil. Volatile compounds seem to be major candidates for the toxic agents in heated oil because oils with rancid and deteriorated odor show strong toxicity.
Used frying oil recovered from food manufacturing companies in Japan and recycled often shows lower carbonyl (COV) and peroxide values (POV) than oil simply heated at 180 degrees C for 20 h does. In this study the reasons for the low COV of oil used for deep-frying were investigated by employing model experiments and actual commercial frying. The results suggested that in actual frying, the factor most influencing the low COV was vaporization of carbonyl compounds, together with steam generated from water contained in frying foodstuffs. It was also suggested that the low levels of COV were attributable partly to inhibition by protein, amino acids exuded from frying foodstuffs, and starch, and slightly to the effects of natural antioxidants in fresh oil and frying foodstuffs, oil absorption by frying foodstuffs, and dilution of oil in use by fresh oil added between uses. On the other hand, the chemical properties of oil in a fryer and in batter coatings of deep-fried foods made with the former oil were checked. Content of polar compounds (PC) and color score were obviously worse in the oil extracted from batter coatings than in that in the fryer, but there were no differences in COV or content of triacylglycerol (TG) of the two oils.
We have previously proposed that thermally processed oil holds promise as a dietary supplement intended for weight loss. We employed a thermal process whereby oil was heated to 180 for 10 h in the absence and presence of gluten. We compared the effects of three diets, untreated oil, heated oil, heated oil and gluten on body weight, retroperitoneal weight and lipid composition and fecal lipid contents. Ten week-old male Wistar rats were fed ad libitum a diet containing 7 wt% of the oil for 12 weeks. The oil heated with gluten showed low levels of food efficiency and oil absorption ratios, and high levels of fecal oil excretion, oil content and bile acid content. Diets containing thermally treated oils resulted in significantly lower retroperitoneal tissue weights and lipid contents as compared to the control group; the groups fed the heated oil and gluten diets showed a general decrease in the fatty acid (especially linoleic acid) amount. In conclusion, oil heated with gluten was not fully digested and thus excreted without showing any detrimental effects on either the organs or feces. This resulted in safe and effective weight loss in growing adult rats.
Male Wistar rats, age 10 weeks, were fed for 11 weeks a commercial powdered diet (no fat) containing 7 wt% fresh frying oil and 0.1 wt% gluten heated in oil at 180 for 10 h followed by filtration. The animals appeared to grow normally and had the same serum levels of glucose, triacylglycerol, phospholipids, and cholesterol as those of a control group fed a diet containing 7 wt% fresh oil. However, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were significantly higher in the test group, and many dark-red patches due to bleeding were observed on the livers of this group. In contrast, rats fed for 11 weeks a diet containing 7 wt% of oil obtained by filtration after the heating described above did not show any damage to the liver or kidneys and showed no gross symptoms. Rats fed a diet containing 7 wt% fresh frying oil and 0.1 wt% gluten heated in a tube at 180 for 10 h did not show any differences from the control group. Analyses of low-molecular-weight compounds in the filtered oil revealed that gluten obviously reduced the level of all the low-molecular-weight compounds (except ethanol) of the oil heated at 180 for 10 h. Thus, it was suggested that gluten reacted with/adsorbed thermally oxidized oil/decomposition products and kept the cytotoxic low-molecular-weight compounds in the chemical structure even after filtration.
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