Research On Simultaneous Rapid Detection Technology Of Frying Oil Waste Index Based On Dielectric Constant

The national standard GB 2716-2018"National Food Safety Standard Edible Vegetable Oil"stipulates that the limit values of total polar compounds（TPCs）and acid value（AVs）of frying oil are 27%and 5 mg KOH/g,respectively,and edible oil exceeding the limit value must be discarded.The traditional detection methods of TPCs and AVs are column chromatography and acid-base titration,which have defects such as large amount of organic solvent and time-consuming.The development of an accurate and efficient rapid detection method for frying oil quality is of great significance for the on-site supervision of frying oil quality.In this study,cottonseed oil and soybean oil were used as frying oil,and noodle cakes,beef balls and sandwichs of three Xinjiang specialties were used as frying ingredients,which were fried at 160°C,170°C and 180°C,respectively.The change law of dielectric constant and waste index（TPCs and AVs）of frying oil in the frying process is studied,and a simultaneous detection model of frying oil waste index based on dielectric constant is established,which provides a theoretical basis for the rapid detection of frying oil waste point.The main conclusions are as follows:（1）The changes of TPCs and AVs of frying oil in the process of frying noodle cakes,beef balls and sandwichs in cottonseed oil and soybean oil at different temperatures were clarified,and the correlation between frying oil TPCs and AVs in the frying process was further analyzed.The results showed that the waste points of frying oil were 24～26 h、24～26 h and 28～30 h during the frying process of noodle cakes,beef balls and sandwichs,respectively.The rise rate of TPCs and AVs of soybean oil is faster than that of cottonseed oil.The TPCs rise rate of frying oil is:noodle cakes,beef balls,and sandwichs,and the AVs rising rate from fast to slow:sandwichs,noodle cakes,beef balls.The frying oil TPCs and AVs had a good positive correlation during the frying process under different conditions,and the R² was above 0.9.（2）The change law of dielectric constant of frying oil in the process of frying noodle cakes,beef balls and sandwichs with cottonseed oil and soybean oil at different temperatures was clarified,and linear regression analysis was carried out on the waste index（TPCs and AVs）and dielectric constant of frying oil.The results showed that the change law of dielectric constant of soybean oil and cottonseed oil in the process of frying the three foods at different temperatures was basically consistent with the change law of their waste index.The waste index of frying oil and the dielectric constant showed a good positive correlation during the frying process under different conditions,and the R² was above 0.9.（3）The linear estimation model and temperature compensation method of frying oil TPCs and AVs based on dielectric constant were established,and the linear regression analysis of the predicted value of the linear estimation model and its true value was carried out.The results show that the linear estimation model of TPCs for frying oil based on dielectric constant is:Y_TPC=0.008X-1004.65（R²=0.9196）,and the linear estimation model for AV is:Y_AV=0.0013X-162.36（R²=0.8618）.The linear slope range of temperature compensation was-20.25～-17.1,and there was a linear positive correlation between the predicted values of TPCs and AVs linear estimation models of frying oil and the true value,and the R² was above 0.9.