Research On Chemical Conversion And Migration Of Benzo(a)Pyrene In The Process Of Frying French Fries With Soybean Oil

Benzo(a)pyrene(BaP)is heavy polycyclic aromatic hydrocarbons with strong carcinogenicity.As an important safety risk factor for frying oils,it is included in the product quality evaluation standard.In the preliminary work of the laboratory,it was found that the BaP content of fried French fries soybean oil decreased significantly,which may be converted into derivatives of unknown toxicity,resulting in the risk of using only BaP content as a food safety evaluation standard.It has been reported that BaP and its derivatives will migrate to fried food and oil fume,but the mechanism is unknown.In order to clarify the chemical conversion and migration mechanism of BaP during soybean oil flying French fries,the following studies are conducted in this paper:First,establish and optimize the pretreatment method for extracting BaP and its derivatives from deep frying oil.Add two standard samples of BaP and oxy-BaP(9,10-dihydrobenzo[a]pyrene-7(8H)-one,abbreviated as BaPO)to the fried soybean oil.The detection limit is the standard evaluation for pre-treatment method and the optimized processing conditions are liquid-liquid extraction-SPE(SI-EMR(Lipid)):three liquid-liquid extractions are carried out using a mixed solvent of acetonitrile/acetone(V:V 9:1).The Si column was eluted with 15 mL toluene/benzene(V:V 1:1).The recoveries of BaP and BaPO were 56.35%and 75.90%,respectively.The detection limits of BaP and BaPO were 0.45 ?g/L and 5.22 ?g/L,respectively.Under this condition,two kinds of BaP derivatives were identified by GC-MS as 9,10-dihydrobenzo(a)pyrene-7(8H)and 7,10-dimethylbenzo(a)pyrene.There is another compound that needs to be further identified due to its match with the temperament database of less than 80%.Then,the effect of each flying conditions on the chemical conversion of BaP-di2(stable isotope)and the amount of BaP-d12 derivatives in oils and fats was studied.The results show that temperature is the most important factor affecting the reduction of BaP-d12 during the frying process.The concentration of fried oil BaP-d12 decreased only by 6.12%after frying at 160? for 10 h,and after frying at 220? for 10 h The loss rate is as high as 58.83%.At the same time,the temperature will also significantly affect the production of BaP-d12 derivatives.No derivative was detected at 160?.The total production of the three derivatives in the initial amount of 1 mg/LBaP-d12 at 220? exceeded 100 ?g/L.In addition,the initial concentration of BaP-d12 in fried oils has a relatively small effect on its conversion during flying.At 1-10 mg/L,the concentration of BaP-d12 decreases by 30%when frying at 200? for 10 h.However,when the initial concentration of BaP-di2 is 10?g/L-1 mg/L,the degree of decrease of BaP-d12 is basically unchanged when the oil is fried for 10 h,and all are maintained at about 50%.The reduction rate of BaP-di2 in fried oil showed a downward trend with the extension of the frying interval.The initial amount of BaP-di2 was inversely correlated with the production rate of BaP derivatives.When oil was fried at 200?for 10 h,the reduction of BaP-d12 during the frying interval of 15,20,25 and 30 min is maintained at 40-50%.When the frying interval is 35 min,the reduction of BaP-d12 is 31.42%.This may be because longer flying intervals and lower frying times slowed down the conversion degree of BaP-d12,but on the contrary promoted the conversion of BaP-d12 in fried oil.Finally,the migration of BaP-d12 in the three phases of fried oil,French fries,and fume was studied.The migration rate of BaP-d12 into oil fume is positively correlated with frying temperature and frying time.The migration rate at 220? is more than twice that of 160?,and the migration rate is significantly higher than 0-6 h in 6-9 h.However,the total amount of BaP-d12 migrated into the fume was very low.After 9 h of flying,only 2%of the BaP-d12 migrated into the fume.The mobility of BaP-d12 in fried oil is affected by the initial amount of BaP-d12 in the fried oil and the frying interval.The mobility of BaP-d12 in potato strips increases slightly with the initial amount of BaP-d12 in fried oil,but it is basically stable in the range of 12-15%.Increasing the flying interval will reduce the amount of potatos fried,thereby reducing the migration rate of BaP in the French fries.