Detection Of Epoxy Triglycerides From Frying Oil By Surface Molecular Imprinting Technology

In the process of frying oil,a large number of polar compounds will be produced,such as triglyceride polymers,oxidized triglycerides（ox-TGs）,hydrolysates and lysates.The content of ox-TGs accounts for about 1/5 of polar compounds,and it has been proved to be the most toxic component among them.However,ox-TGs refers to a class of triglycerides with complex structures,which may contain aldehyde,hydroxyl,epoxy,carbonyl and other groups.Most previous studies focused on mixed ox-TGs,which also led to the unclear oxidation mechanism and toxicity mechanism of ox-TGs.Therefore,it is urgent to systematically establish a method that can accurately identify,separate and detect the structure of ox-TGs compounds.Molecular imprinting technology is a technology that can specifically separate certain molecules.At present,it has been successfully applied to the separation of isomers,enantiomers and natural products.Based on surface molecular imprinting polymer technology,a method for the combination of molecular imprinting and UV spectroscopy has been established.（1）This paper systematically studied the changes of TPC content,acid value,peroxide value and anisidine value of palm oil,high oleic peanut oil,sunflower seed oil with time at different frying temperatures.The effects of frying temperature and frying time on the composition and content of ox-TGs in the three oil samples were analyzed by HPLC-MS.It was found that the most important ox-TGs are epoxy triglyceride,then is monohydroxy triglyceride,and the content of aldehyde-epoxy triglyceride was the least.The formation rate of monoepoxy triglyceride and dihydroxy triglyceride is relatively slow,and the content of monoepoxy triglyceride and dihydroxy triglyceride increases relatively quickly with the increase of temperature.（2）In this study,1-epoxy stearic acid and 2,3-glyceryl oleate（EOO）were selected as the representative epoxy triglycerides as the analysis targets,and the imprinted polymers coated on nano Fe₃O₄ particles were synthesized（Fe₃O₄@MIPs）.In order to obtain good selectivity and recovery Fe₃O₄@MIPs,these synthesis conditions of Fe₃O₄@MIPs were optimized.It was found that the adsorption capacity of the product was the largest when acrylamide（AM）was used as the functional monomer and dichloromethane（DCM）was used as the solvent at 60℃for 28 hours.Synthesized under this condition Fe₃O₄@MIPs Transmission electron microscope（TEM）and scanning electron microscope（SEM）were used to determine the apparent morphology.It was found that the surface of Fe₃O₄ was covered with a gray imprinted layer more than that of Fe₃O₄,and its structure was better than that of non-imprinted polymer Fe₃O₄@NIPs Rough.The selectivity and adsorption properties of the imprinted particles were evaluated by equilibrium binding experiments.The results showed that the imprinted particles had high adsorption capacity（58.32±1.61 mg/g）,stable equilibrium adsorption time（45 min）and good specificity（the separation factor reached 6.07）.The structure was characterized by SEM,TEM,FT-IR and XRD.The selectivity and adsorption performance of imprinted particles were evaluated by equilibrium binding experiment.The results showed that these imprinted particles had high adsorption capacity（58.32 mg/g）,stable equilibrium adsorption time（45 min）and good specificity（the separation factor reached 6.07）.These Fe₃O₄@MIPs materials produced a large number of active recognition sites in the synthesis process,so it can specifically recognize when encountering EOO.（3）A highly selective magnetic solid phase extraction（MSPE）method was established by using imprinted particles as adsorbent.The MSPE conditions were optimized and combined with UV spectroscopy to determine epoxy triglycerides in frying oil.It was found that the method had a good linear relationship in the range of 0.20-1.00 mg/L（R²=0.997）,and the detection limit of epoxy triglycerides was 0.0599 mg/L;Fe₃O₄@MIPs Particles can be reused for more than five timesA highly selective MSPE method combined with UV spectroscopy was established to determine epoxy triglyceride in frying oil,and the parameters affecting the performance of MSPE were optimized.This method has a low detection limit of the epoxy triglyceride（0.0599 mg/L）,and it has a perfect linear relationship within the scope of.It can not only specifically separate epoxy triglycerides,but also provide a powerful idea for detecting other ox-TGs from fried oil.The established method can not only specifically separate epoxy triglycerides from frying oil,but also has significant selectivity,low detection limit and good stability.In addition,it provides a powerful idea for separating other ox-TGs from frying oil and provides support for the safety control of frying food industry.