Study On The Relationship Between Total Polar Components And Triglyceride Polymers And Other Components In Frying Process

In this paper,the changes of levels of total polar compounds(TPC),oxidized triglycerides polymers(TGP),polycyclic aromatic hydrocarbons(PAHs),acid value,trans fatty acids,Vitamin E and phytosterol when frying wtih different type of oils,different frying methods and different frying food were studied.This is the first time analyzed the correlations between TPC and PAHs,between TPC and PAHs in frying oil in China.Besides,this paper discussed the concentrations of TGP and PAHs when the TPC value reached the Chinese standard of 27%.This work also compared the levels of TPC,TGP and PAHs between fried food and frying oil.The study cause great concern to ensure the safety of frying oil comprehensively,and provided basic data for further study.(1)Dough sticks were fried continuously on rapeseed oil,sunflower oil,peanut oil,soybean oil and palm oil,then the changes of the value of TPC,TGP,PAHs,acid value,trans fatty acids,Vitamin E and phytosterol of fried oil were investigated,and the correlation between TPC and PAHs,between TPC and PAHs were analyzed.The results showed that: TPC in rapeseed within 27% after frying for 32 h,while sunflower,peanut,soybean and palm oil exceeded 27% after frying for 28 h,32 h,32 h and 30 h,respectively.TGP in rapeseed,sunflower,peanut,soybean and palm oil were respectively at 15.55%,18.81%,14.28%,15.44% and 11.97% when TPC within the established acceptable concentration in China(27%).However,TGP were already exceeded the standard level when comparing with the limited concentration in Belgium and the Czech republic(?10%).BaP were within 10 ?g/kg in Chinese standard,while the time for exceeding European Union standard were advanced;the acid value in sunflower and peanut oil exceed 5 mg/g after frying for 28 h and 20 h,respectively;the value of TFA increased and there were different loss degrees of the concentrations of VE and phytosterol.TPC was significantly and positively linear correlated with TGP and PAHs during frying.The relationship between TPC and TGP was not related to oil types.(2)Dough sticks,potato chips,bean curd and chicken wing were continuously frying on peanut oil,making heated peanut oil(named blank)as a control group.After detecting the risk and nutrients components in each frying oil,the results showed that: TPC in bean curd fried oil was within 27% after frying for 32 h,while blank,dough sticks,potato chips and chicken wing fried oil exceeded 27% after frying for 16 h,32 h,24 h and 30 h,respectively.TGP in blank,dough sticks,potato chips,bean curd and chicken wing fried oil were respectively at 35.60%,14.28%,22.80%,4.91% and 17.31% when TPC within the established acceptable concentration in China(27%).BaP were all within 10 ?g/kg in Chinese standard,while exceeded 2 ?g/kg(European Union standard)in fresh oil.The acid value in dough sticks fried oil exceeded 5 mg/g after frying for 20 h,the value of TFA increased and there were different loss degrees of VE and phytosterol concentrations.TPC was significantly and positively linear correlated with TGP and PAHs during frying.And were not related to food types.(3)Blank,dough sticks,potato chips,bean curd and chicken wing were intermittent frying on peanut oil for 5 consecutive days(each day fried for 3 h).After detecting the risk and nutrients components in frying oil,the results showed that: TPC in blank,dough sticks,potato chips,bean curd,chicken wing fried oil were within 27%(Chinese standard),and TGP respectively increased to 6.03%,10.86%,15.29%,5.68% and 15.76%,they were all at high levels except for blank and bean curd fried oil;BaP were within 10 ?g/kg in Chinese standard,while exceeded European Union standard in fresh oil;acid value were all within the limited levels of 5 mg/g;the value of TFA increased and there were different loss degrees of VE and phytosterol concentrations.TPC was significantly and positively linear correlated with TGP during frying.And were not related to food types and frying method.TPC had no significantly correlated with PAHs when blank frying,while were significantly correlated with BaP,PAH4 and PAH16 in other frying process.(4)After analyzing the levels of TPC,TGP and PAHs in oil extracted from dough stick during intermittent and continuous frying process with peanut oil,the results showed that: TPC in oil extracted from dough stick didn't exceed the limit of 27% in frying oil,while TGP respectively increased to 12.11% and 15.60%,which exceeded the permitted concentration of 10% in other countries.After frying,the contents of TPC and TGP in oil extracted from dough stick was slightly higher than that of the corresponding frying oil samples.And PAHs in oil extracted from dough stick were significantly higher than in frying oil.TPC in the oil extracted from dough stick was significantly and positively linear correlated with TGP during intermittent and continuous frying process,and were not related to frying method;TPC was significantly linear correlated with PAHs during intermittent frying process,and had no significantly correlated linear with PAHs during continuous frying process.Therefore,using only the TPC content as an indicator of the safety of frying oil does not seem to be objective,the concentrations of TGP and PAHs in frying oil should also cause great concern to ensure the safety of frying oil comprehensively.