Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In...Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In this study, the authors used an ESR spin-trapping method to study the oxidation of triacylglycerols （TAG） containing different fatty acids （FAs） commonly found in food. The ESR adduct signals were analyzed to study the effect of double bonds and the chain length of the FAs of TAG on oxidation. Oxidation was conducted by applying UV irradiation to TAG by dissolving it in N-tert-buthyl〈t-phenylnitrone （PBN）, which trapped the radicals induced in the TAG as an ESR adduct signal. The detection was clearly successful. There were no differences in the spectra of tristearin （18：0） and tripalmitin （16：0）; thus, it can be concluded that the length of the carbon chain of the FAs of TAG does not affect the oxidation reactions. However, the ESR spectra of tristearin （18：0）, triolein （18：1） and trilinolein （18：3） were clearly different due to the presence/absence of a new peak corresponding to new induced radicals, leading to the conclusion that double bonds play a major role in the oxidation reactions of fats and oils.展开更多
A process for the production of glycerol carbonate(GC) is proposed with the transesterification of glycerol(GL)and dimethyl carbonate(DMC) with CaO as catalyst by reactive distillation and extractive distillation. The...A process for the production of glycerol carbonate(GC) is proposed with the transesterification of glycerol(GL)and dimethyl carbonate(DMC) with CaO as catalyst by reactive distillation and extractive distillation. The performance of solvents in separating DMC-methanol azeotrope and the effects of operation parameters on the reactive distillation process are investigated experimentally. The results indicate that both the GL conversion and GC yield increase with the DMC/GL molar ratio, reflux ratio, final temperature of tower bottom, and CaO/GL molar ratio and decrease as the recycle number of CaO increases. The calcium concentration in the residual reaction mixture also decreases remarkably as the DMC/GL molar ratio increases. At DMC/GL molar ratio 4.0, reflux ratio 1.0, final temperature of tower bottom 358 K, and CaO/GL molar ratio 0.05, both the GL conversion and GC yield can reach above 99.0%, and the mass concentration of calcium in the product is less than 0.08%.展开更多
文摘Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In this study, the authors used an ESR spin-trapping method to study the oxidation of triacylglycerols （TAG） containing different fatty acids （FAs） commonly found in food. The ESR adduct signals were analyzed to study the effect of double bonds and the chain length of the FAs of TAG on oxidation. Oxidation was conducted by applying UV irradiation to TAG by dissolving it in N-tert-buthyl〈t-phenylnitrone （PBN）, which trapped the radicals induced in the TAG as an ESR adduct signal. The detection was clearly successful. There were no differences in the spectra of tristearin （18：0） and tripalmitin （16：0）; thus, it can be concluded that the length of the carbon chain of the FAs of TAG does not affect the oxidation reactions. However, the ESR spectra of tristearin （18：0）, triolein （18：1） and trilinolein （18：3） were clearly different due to the presence/absence of a new peak corresponding to new induced radicals, leading to the conclusion that double bonds play a major role in the oxidation reactions of fats and oils.
基金Supported by the National Natural Science Foundation of China(21106050)Specialized Research Fund for the Doctoral Program of Higher Education(20100142120066)
文摘A process for the production of glycerol carbonate(GC) is proposed with the transesterification of glycerol(GL)and dimethyl carbonate(DMC) with CaO as catalyst by reactive distillation and extractive distillation. The performance of solvents in separating DMC-methanol azeotrope and the effects of operation parameters on the reactive distillation process are investigated experimentally. The results indicate that both the GL conversion and GC yield increase with the DMC/GL molar ratio, reflux ratio, final temperature of tower bottom, and CaO/GL molar ratio and decrease as the recycle number of CaO increases. The calcium concentration in the residual reaction mixture also decreases remarkably as the DMC/GL molar ratio increases. At DMC/GL molar ratio 4.0, reflux ratio 1.0, final temperature of tower bottom 358 K, and CaO/GL molar ratio 0.05, both the GL conversion and GC yield can reach above 99.0%, and the mass concentration of calcium in the product is less than 0.08%.
