Quality Changes Of Edible Oil In Frying And Research On Rapid Detection Technology Of Polar Compounds

Frying technology is widely used in food industry all over the world.With its fragrant,crisp and other quality,fying food has become famous in the world.The consumption is increasing every year.When people enjoyed delicious,they didn't pay attention to the harm of frying oil,which would occur a series of physical,chemical changes in high temperature.The changes would decrease the value of food,form a lot of toxic substances,and would be harmful to people's health.Some researcher did a large number of research in quality evaluation of frying oil,but most of them were focus on one of aspects instead of systematically study.Besides,the study of rapid detection technology of polar compounds were limited in the world.The rapid detection technology such as HPLC,NLR,NMR,electronic nose was used widely in aboard,but the technology didn't meet the needs of rapid detection.Therefore,it was important to study the effect factor of the genetation of polar compounds,the quality changes of oil in frying,the development of rapid detection technology of polar compounds.In this paper,fresh soybean oil,colza oil,peanut oil and palm oil were picked to frying different food in different time and different temperature.The column chromatography was used to determine the content of polar compouds of flying oils, analyse the variation tend of the content of polar compouds in frying oils.The fluorescent spectrometry was used to determine the changes of fluorescence intensity of frying oils.The chemical index such as POV,acid number,the content of polar compounds,absorbency,chromatic aberration,refraction index,viscosity,were used to study the quality changes of frying oils.The electrical conductivity was used to determine the conductivity of frying oils.The results were as follows,①The polar componets content increased with the increasing of frying time.From two hours to four hours,the content of polar compounds was increasing slowly,when keep frying eight hours,the content of polar compounds was 22.32%,when keep frying ten hours,the content of polar compounds was 27.05%which exceeded the limit value ruled by national standards,therefore,the suggestion was that the frying time should be no more than 8 hours.②The polar componets content increased with the increasing of frying temperature.When fying tempetature was 240℃,the content of polar compounds was 30.61%,when the temperature was 220℃and 200℃,the content of polar compounds was 26.40%,25.60%,which exceeded the value ruled by national standards.When fying temperature was 160℃,the fying time needed longer time,and the fying food was easy to asorb oil.therefore,the suggestion was that the best frying temperature of frying oil was 180℃.③in the same time,the content of polar compounds in soybean oil,colza oil, peanut oil and palm oil increaed by 9.68%,7.14%,20.32%,5.10%.It was easy to know that the add value of palm oil was least.So,it was suitable to choose palm oil as fying oil.④In the same temparature,the peroxide value,refractive index,decreased,acid number increased at first and then decreased and increased again,polar componets, chromatic aberration,refraction index,viscosity increased with the increasing of frying time,absorbancy decreased step by step.In the same frying time,the peroxide value and absorbance decreased with the increasing of frying temparature,acid prices decreased at first and then increased.Polar components,chromatic aberration,refractive index,and viscosity incresed step by step.Besides,the variety of fying oils and fying foods were also the effect factor of quality changes of frying oil.⑤The fluorescence intensity wave crest of frying oils moved to the direction of the larger wavelength.The fluorescence intensity decreased sharply in the four hours, but afer four hours,the fluorescence intensity didn't change much more.⑥The content of polar compounds in fying oil had good correlation with electrical conductivity,the correlation coefficent was 0.9737,0.9835,0.9583,0.9645.The relative standard deviation was 2.78%-4.27%,The correlation was 0.9862.Electrical conductivity had strong correlation with Column chromatography. Summerize:The frying time should be no more than 8 hours and the best frying temperature of frying oil was 180℃,choose palm oil as lying oil.The fluorescence intensity wave crest of frying oils moved to the direction of the larger wavelength.The electrical conductivity had strong correlation with Column chromatography.The electrical conductivity could substitude the column chromatography for determining the polar components of frying oil.