| Edible oil frying is a complex physical and chemical process.In continuous high temperature conditions,the oil is prone to thermal polymerization,thermal decomposition,thermal hydrolysis and other reactions,while frying food materials also have a certain impact on the quality of frying oil.In the high temperature conditions,Fried food with attractive fragrance,unique taste,golden color loved by people,but a long time high temperature frying or improper frying can bring safety risks,such as polar components(TPC),oxidized triglyceride polymers(TGP),polycyclic aromatic hydrocarbons(PAHs),trichloropropanol esters(3-MCPD esters),trans fatty acids(TFA)and other harmful substances.That is the risk of food safety.In the intermittent frying process,many kinds of fried oils of different materials fried in peanut oil were tested and analyzed.The purpose of this study was to investigerate and analyse the content of 3-MCPD esters and GE esters in the fried oils of different food materials.The safety of fried oils were evaluated to use.In the continuous frying process,experiment in the same oil to fry.The purpose of this study was to investigerate and analyse the content of 3-MCPD esters and GE esters in the fried oils of different fried way(continuous frying,intermittent frying).Five different kinds of fats and oils were used to fry deep-fried dough sticks for continuous frying 32 h without any time lag.The purpose of this study was to investigerate and analyse the content of 3-MCPD esters and GE esters in the different kinds of fried oils and fried food.This research would provide a technique support for ensuring the quality and safety of fried oil and fried food.French fries,chicken,bean curd,deep-fried dough sticks and blank test were experimentally fried(intermittent frying,early,middle and late every 1h,5 consecutive days)in peanut oil.In addition,the contents of 3-MCPD esters,GEs and TPC in the oil samples collected from different frying time were detected and analyzed.The results showed that when fried for 3h,the content of 3-MCPD esters in different frying food materials(french fries,chicken,bean curd,deep-fried dough sticks and blank test)were tested of frying peanut oil and the content of 3-MCPD esters were from 0.84mg/kg(initially)to 2.17,11.02,4.60,9.96,and 5.41 mg/kg.When fried for 15h,the 3-MCPD esters in above-mentioned frying oil were 1.58,11.81,12.88,3.51 and 3.72 mg/kg,respectively.The content of GEs increased from 2.43mg/kg to 9.06,40.36,9.00,46.47 and 47.05 mg/kg after frying 15h,respectively.The increased content of frying food materials were different from each component during the high temperature frying process.The results showed that the highest content of 3-MCPD esters was bean curd and chicken while the content of GEs was chicken,deep-fried dough sticks and blank test.At the end of the intermittent frying 15h,the Polar Components(TPC)and acid values of the five kinds of fried oil samples were not exceeding the national standard limit.But refer to the EU's limited standards(the maximum content of 3-MCPD in condiment was 0.02mg/kg,and the maximum amount of GEs in vegetable oil was 1 mg/kg),the increase value of 3-MCPD esters and GEs in frying process has exceeded the safety limit.Therefore,the risk of food safety caused by 3-MCPD esters and GEs of frying oil and even fried food should be highly concerned.A comparative experiment was conducted to study the effects of different frying processes on the 3-MCPD esters,GEs,polar components and others by using different frying methods-continuous frying and intermittent frying in the second section.The results showed that the content of 3-MCPD esters in different frying food materials(deep-fried dough sticks,french fries,chicken,bean curd and blank test)of continuous frying 32 h were tested and the content of 3-MCPD esters were from 0.84 mg/kg(initially)to 2.08,2.96,17.45,7.12,8.02 mg/kg at 12h,4h,12h,16h and 8h,respectively.This were the higstest content of 3-MCPD esters in the fried oils and after that they were decrease.The content of GEs increased from 2.43 mg/kg(initially)to 20.80,7.20,5.00,2.10 and 66.34 mg/kg at the end of 32h frying.While taking the same way of frying,the total contents growth of 3-MCPD esters,GEs and TPC in different frying materials have a difference,the growth of GE content in blank frying oil is the largest,the growth of 3-MCPD esters in frying oil of bean curd and chicken wings are largest.At the end of continuous frying 32 h,the total amount of 3-MCPD esters and GEs in different frying oils was blank test 70.05 mg/kg>deep-fried dough sticks 21.48 mg/kg>bean curd 12.93 mg/kg>french fries 8.51 mg/kg>chicken 6.60 mg/kg.When the TPC reached the limit(27%),the corresponding of five kinds of fiying oil was deep-fried dough sticks 32h,chicken wing 28h,French fries 24h and blank test 16h out of limit,but bean curd was not exceeded all the time.The content of TPC in five kinds of frying oil was 29.00%,32.98%,36.47%,50.66%and 15.50%at the end of frying 32h,respectively.In addition,the total amount of 3-MCPD esters,GEs and TPC in continuous frying oils is smaller changes than that in the intermittent frying oils.It meant that the quality of the oil was not easy to deteriorate.Therefore,no matter the intermittent frying or continuous frying,the content of 3-MCPD esters,GEs and TPC in the frying process increased obviously,which caused the food safety risk of frying oil should not be ignored.Sunflower oil,rapeseed oil,soybean oil,palm oil and peanut oil were used as cooking oils for the deep-frying of deep-fried dough sticks for continuous frying 32 h without any time lag.The purpose of this study was to investigerate and analyse the content of 3-MCPD esters,GE esters,TPC,VE and so on in the different kinds of fried oils.The results showed that the content of 3-MCPD esters in peanut oil was increased(largest amounts was 2.08 mg/kg)at 12h and then discrease and the others decreased all the time with the extension of frying time.When fried for 32h,the content of 3-MCPD esters in sunflower oil,palm oil,peanut oil,soybean oil and rapeseed oil frying oil were from 0.70,7.57,0.84,1.21 and 1.67 mg/kg(initially)to 0.26,0.68,0.67,0.69 and 0.41 mg/kg,respectively.The content of GEs in rapeseed oil descreased to 2.48 mg/kg at 16h and then increased and the content of GEs in palm oil descreased to 1.63 mg/kg.The content of GEs in the peanut oil,sunflower oil and soybean oil increased from 2.43,1.39 and 1.92(initially)to 20.80,11.27 and 3.66 mg/kg.The content of TPC and acid value of the frying oil gradually increased with the frying time;the content of TPC increased to sunflower oil 34.19%,palm oil 29.18%,peanut oil 29.00%,soybean oil 27.11%,and rapeseed oil 25.80%at the end of frying.When the TPC reached the limit(27%),the corresponding of five kinds of frying oil was sunflower oil 28h,palm oil 30h,peanut oil 32h,soybean oil 32h,but rapeseed oil was not exceeded all the time.Peanut oil and sunflower oil exceeded the limit at the end of frying and the other three kinds of frying oil did not exceed the standard.The amount of 3-MCPD esters in fried dough sticks of different frying oils(peanut oil,sunflower oil and soybean oil)increased first and then decreased;the content of 3-MCPD esters in fried dough sticks of rapeseed oil and palm oil was consistently decreasing.The amount of GE esters in fried dough sticks of peanut oil and sunflower oil increasesd significantly along with the frying time,while the other fried dough sticks with different frying oils gradually decreased.Compared with 3-MCPD esters in fried oil,the content of soybean oil and rapeseed oil was higher than that in the corresponding fried dough sticks.The content of 3-MCPD esters in fried dough sticks was higher than that in the fried oil.However,the content of 3-MCPD esters in the fried dough sticks was more complex in palm oil and peanut oil.Compared with fried oil,the amount of GEs in most of fried oil was higher than that in fried dough sticks.In summary,3-MCPD esters and GEs are commonly found in fried oil and fried foods,and the contents of both are generally slightly lower in fried foods than in fried oil;the harmful ingredients are relatively low during continuous frying and it is more suitable for frying;for the different ingredients frying,it is necessary to select the appropriate frying oil.For example,when the peanut oil was used as the flying oil,the french fries and the fried dough sticks should be selected for continuous flying.But the fried dough sticks was used as fried ingredients should be selected soybean oil for continuous flying,thereby reducing the generation of harmful substances to protect the safety of fried oils and fried foods.The results of this paper are of great significance to the control of risk components,the development of frying oil and the quality safety of Fried food in the flying industry. |
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