Study On The Change And Regulation Of Polar Compounds During Edible Oil Oxidation Process

Edible oils undergoe a series of chemical reactions and produce polar compounds(PC)during storage and processing,which are mainly oxidized triglyceride oligomers(TGO),oxidized triglyceride dimers(TGD),oxidized triglyceride monomer(ox-TGM),diacylglycerols(DG),monoglycerides(MG),free fatty acid(FFA)and so on.They can comprehensively reflect the degree of oxidation of edible oil,and are widely used to evaluate the quality of edible oil.At present,the research on PC of edible oil is mainly focused on frying oil,but there are few reports on the production and change of PC of edible oil under mild conditions.In order to further enrich the theory of lipid oxidation,new methods were established to rapidly determine the PC content of edible oil;the relationship between PC and quality of edible oil was studied in different oxidation processes;the changes of PC components of edible oil were explored during different oxidation processes(stir-fried potato shredded,room temperature storage and 63 ~oC oven treatment);the effects of adding different substances(TBHQ,2,2’-Azobisisoheptanenitrile and chlorophyll)to edible oils on the production of PC components were explored.The study reveals the changes and regulation of PC in edible oil during different oxidation processes.The main results are as follows:(1)Two methods based on attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy and polyethylene-film-based Fourier transform infrared(PE-FTIR)are used to determine the PC content of edible oil.Calibrations of the PE-FTIR and ATR-FTIR spectroscopy measurements provide correlation coefficients of 0.9930 and0.9972,respectively,and root mean error of calibration of 1.55 and 0.75%,respectively.PE-FTIR and ATR-FTIR are considered adequate for analytical purposes and provide root mean error of prediction values of 2.90 and 3.10%for blind sample validation,respectively.The PE-FTIR technique provides better prediction results than the ATR–FTIR technique.The PE-FTIR and ATR-FTIR techniques can be applied to rapidly determine the PC content of edible oils.(2)The relationship between the peroxide value(PV),PC content and fatty acid composition of four common edible oils was explored under different conditions.The PC content in edible oils increased significantly with the increase of PV under the condition of stir-fried potato shredded(except linseed oil)and oven treatment,while the PC content fluctuated in other oxidation process;the linseed oil with high linolenic acid content(up to50%or more)produced higher PC than other edible oils in the same oxidation process.The above results indicate that the fatty acid composition has a great influence on the production of PC in edible oils.For the study of the changes of fatty acid composition of edible oil in different oxidation processes,the content of palmitic acid,stearic acid and oleic acid increased significantly with the increase of PV under the condition of stir-fried potato shredded(soybean oil and peanut oil)and oven treatment.The content of linolenic acid significantly reduced.The content of fatty acids in edible oils did not change significantly or fluctuated under other treatment conditions,indicating that the oxidation temperature had a greater effect on the fatty acid composition of edible oils.(3)Using high performance size exclusion chromatography(HPSEC)technology to explore the relationship between PC components and PV in different oxidation processes(oven treatment,room temperature storage and stir-fried potato shredded)of four edible oils.The content of oxidative polymerization part of four edible oils was higher than that in hydrolyzed part during different oxidation processes,indicating that the oxidation reaction was more prominent.In the same process,the change of PC components in linseed oil was more obvious than other oils.Under the same process,the proportion of oxidative polymerization part increased with the increase of PV,and the product was dominated by ox-TGM.While the secondary oxidation product represented the proportion of TGO and TGD was less.DG has a higher proportion than MG and FFA,which is always the main component of the hydrolyzed part.The content of each component of the hydrolyzed part did not change significantly or fluctuated with the increase of PV.(4)A certain amount of TBHQ,chlorophyll and ABVN were added to four edible oils,respectively.The collected samples were analyzed by HPSEC technology.When the same substance was added,the content of oxidative polymerization part of four edible oils was higher than that in hydrolyzed part,indicating that the oxidation reaction was more prominent.With the increase of PV,the addition of TBHQ can regulate the content of oxidized part in peanut oil and rapeseed oil to some extent,thus delaying its oxidation;in other cases,with the increase of PV,the content of PC components fluctuated or did not change significantly.In addition,the content of oxidative polymerization part of linseed oil is significantly higher than the other oils,which may be due to the higher linolenic acid content of linseed oil.ABVN and chlorophyll can significantly increase the rate of automatic oxidation of oil,resulting in oxidative rancidity and degradation of edible oil.Therefore,proper addition of antioxidants,protection from light and removal of free radical initiators are effective measures to improve the oxidative stability of edible oil.