Detection Of Edible Vegetable Oil Quality And Study Of Early Warning Indicators

The quality of edible oils and fats has a direct impact on health and quality ofpeople. In recent, the frequent occurrence of waste oil, deterioration of oil and otheredible oil safety incidents have caused people to panic, which have already drawn closeattention from the central and local government of China. The quality and safety ofedible oil is mainly derived from two aspects, one is the artificial introduction ofnon-edible oil in edible oil; the other is the edible oil deteriorations during in the storageand using process.Based on the studies about the vegetable oil (canola oil, corn oil, soybean oil,sesame cooking oil, etc) and catering waste oil (hot pot of oil, chinese oil, etc) of acidvalue, peroxide value, conductivity, total polar material, trans fatty acids, cholesterol,freezing experiments and the oxidation stability, both optimal analytical methods andthe best experimental operating conditions are gained, which provide a more rapid andaccurate detection method for vegetable oil quality monitoring.The researche contents and the research results are listed below.1. Under both light and dark storage conditions, compare the acid value andperoxide value on different types, different techniques, different grades of the ediblevegetable oil. After five months, continuous light, the experimental results show thatthe acid value and peroxide value of vegetable oil reachs3.98mg(KOH)/g and126.70mmol/kg, while the catering waste oil reachs7.80mg(KOH)/g and254.10mmol/kg,which seriously exceed the national limits.2. Compared the results between the force standard methods and TESTO-0265total polar substances detector on the detection of total polar substances in thevegetable oil. The results show that TESTO-0265instrument and the GB method fordetection has no significant difference, both can be used for the detection of totalpolar substances in the edible vegetable oil. However, TESTO-0265total polarsubstances detector has better reproducibility, which RSD ranges from0.00%to2.34%, this method can quickly and effectively detect polar substances in the edibleoil.3. Optimize experimental conditons(types of water, types of organic solvents, different extraction methods, the volume of water, the volume of organic solvent).After detecting the electrical conductivity of edible vegetable oils and restaurant wastegrease, the results show that the conductivity of edible vegetable oil samples are lessthan10μs/cm, while the electrical conductivity in catering waste oil samples rangesfrom80μs/cm to100μs/cm.4. Apply gas chromatography to detect trans fatty acid content in the ediblevegetable oil samples. The experimental results show that the trans fatty acid contentis0.15%-0.98%in the corn oil,0.99%-2.59%in the soybean oil,0.18%-1.18%in the rapeseed oil,1.05%-2.10%in the sesame oil,0.23%-0.90%in the sesamecooking oil. Based on the analysis of sample trans fatty acid content data, it found thatthe trans fatty acid content in the vegetable oil that is produced by the leachingprocess is higher than by the pressing process, and the higher the refining degree, thehigher the trans fatty acid content.5. Freezing test on edible vegetable oils and restaurant waste grease. The resultsshow that the common vegetable oil is transparent flow liquid at-5℃, while cateringwaste oil is opaque semi-solid at0℃and solidification at-5℃, which indicate thatcatering waste oil contains animal oil.6. Establish gas chromatography to detect cholesterol content in the vegetable oil.The linear area is in the range of0.002-0.5mg/mL. The correlation coefficient is r=0.9997. The method detection limit is at20mg/kg. The recovery rate ranges from81.3%to93.8%. The method precision is good (RSD=1.104%).7. Establish gas chromatography-mass spectrometry to detect cholesterolcontent in the vegetable oil. The best instrument conditions are gained, which includeion source temperature at230℃, injection volume at1.0μL, column flow rate at2mL/min, splitless and the detection limit at4mg/kg. Combined with actual samples ofall kinds of edible vegetable oil, according to the detect results, the cholesterol50mg/kg is early warning value in the identification of fats and vegetable oils.8. Investigate the oxidative stability on the different types of edible vegetable oiland animal oil. The results show that the oxidative stability is different, includingsesame oil that contains more antioxidants oxidative stability values is largest, themost stable, while the oxidative stability of edible vegetable oil that is produced bypressing process is higher than by the leaching process.9. Set up early warning indicators and early warning value of problem grease. Bydetection and study, cholesterol is as to early warning indicators of problem grease,and early warning value is set to50mg/kg.