Effects Of Natural Antioxidant On The Polycyclic Aromatic Hydrocarbons(PAHs) Formation Of Fats And Fatty Acids During Being Electrical Roasting

Polycyclic aromatic hydrocarbons（PAHs）are classified as carcinogens by International Agency for Research on Cancer（IARC）tissues.Acute or chronic exposure can cause toxicity,carcinogenicity and teratogenicity to human body.For non-occupational exposure to PAHs and non-smokers,dietary exposure accounts for 70%of total PAHs exposure.In diet,processed meat products made by barbecue,smoking and frying contain a large amount of polycyclic aromatic hydrocarbons（PAHs）.Existing literatures believe that the sources of PAHs in meat products are fat,protein,carbohydrate and other substances in meat through pyrolysis reaction,and studies have shown that the presence of fat has a significant impact on the formation of PAHs in meat products.Therefore,it is of great significance to further study the changes experienced in the process of polycyclic aromatic hydrocarbons（PAHs）formation from fat by thermal processing and the way in which natural antioxidants act on this process.Therefore,the purpose of this study was to investigate the effects of different animal fats（sheep fat,duck fat and pig fat）on PAHs production and changes in the composition of fats,and to find out the distribution of polycyclic aromatic hydrocarbons（PAHs）and the infrared spectra of pyrolysis products during the processing.The key substances and possible pathways of polycyclic aromatic hydrocarbons（PAHs）are studied,and the role of natural antioxidants in this process is explored.The mechanism of PAHs from fats processed and the mechanism of natural antioxidants are revealed,which can guide human to process meat reasonably and prevent diseases.This study mainly includes the following three parts:1.Effect of animal fat types on PAHs formation and analysis of fat composition changes during electric bakingThree kinds of animal fat（sheep fat,duck fat and pig fat）were processed by 240 degree C roasting and 30min processing respectively.The production and distribution ofPAHs and the contents of fat components before and after processing were detected.The results showed that:1)three kinds of animal fat（sheep fat,duck fat and pig fat）were produced after 240min C 30 min,the production of PAHs was different:the total PAHs production of the duck fat was 741.4 after the roasting,and the total PAHs of sheep fat and pig fat reached 694.65ng/g and 695.51ng/g respectively.Among all PAHs detected,Anl production was the highest,and BkF production was the lowest.Anl,Flu,Phen and Flt four PAHs with less number of PAHs in duck fat group were significantly higher than sheep fat and pig fat,while Ant,Pyr,Chry,BkF and BaP production did not differ between the three groups.2)By analyzing the fatty acid composition of three kinds of animal fats,it was found that sheep fat had higher C10:0,C12:0,C14:0 and C18:0 saturated fatty acid content,duck fat had higher C18:1,C18:2 and C18:3 unsaturated fatty acid content.Therefore,the Cox value of duck fat was higher than that of sheep fat and pig fat.The Cox values were 2.83 and 2.44 before and after processing,respectively.The Cox values of sheep fat and pig fat before and after processing were 0.81 and 0.54,respectively,and 2.13 and 1.98 respectively.It shows that the unsaturated degree of three kinds of animal fat is duck fat>pig fat>sheep fat.3)by analyzing the contents of fat components（NL,FFA and PL）before and after the processing of three kinds of animal fat,it was found that the components of three kinds of animal fat after electric baking were lower than that before electric baking.The NL content in sheep fat was significantly different before and after electric baking.The FFA content in pig fat was significantly different before and after curing,and PL did not show significant difference before and after processing three kinds of fat.2.Effect of Fatty Acids on the Formation of Polycyclic Aromatic Hydrocarbons and Analysis of Intermediate Products of Fatty Acids from Pyrolysis to Polycyclic Aromatic HydrocarbonsSix kinds of FAMEs（methyl myristate,methyl palmitate,methyl stearate,methyl oleate,methyl linoleate and methyl linoleate）were baked at 240℃ for 30 minutes,respectively.The formation and distribution of polycyclic aromatic hydrocarbons（PAHs）after baking were detected,and the pyrolysis products of the FAMEs were detected by TG-FTIR.The results showed that:1)The amount of PAHs produced by six kinds of FAMEs（fatty acid methyl esters）after electro-baking was different:the amount of PAHs acids being electrical roasting increased with the increase of carbon content and unsaturation degree of fatty acids,and the total PAHs produced by methyl linolenate after electro-baking reached 898.37ng/g,which was significantly higher than the other five groups;among the detected PAHs,Anl produced the highest amount,B.The production of bF,BkF and Ant is low.It was found that the thermal processing loss in the process of electro-baking of FAMEs had the opposite trend to that of PAHs:the thermal processing loss decreased with the increase of carbon content of fatty acids,and it had nothing to do with the degree of unsaturation of fatty acids.2)The infrared data of fat pyrolysis products by TG-FTIR analysis model were consistent with the data of PAHs formation.The absorption peaks of pyrolysis products increased with the increase of carbon content and unsaturation degree of fatty acids,and obvious olefin characteristic absorption peaks were found at 3013cm^-1 in the pyrolysis products of methyl linoleate and methyl linoleate.Infrared absorption of the pyrolysis products of the model lipids began to appear at about 165℃,and the maximum infrared absorption occurred at 306℃.3)By analyzing the amount and distribution of PAHs in FAMEs after electro-baking,and combining with the relevant literature and the study of PAHs formation mechanism,it is found that the formation and growth of PAHs in fatty acids during thermal processing are dominated by the addition of alkanes and/or olefins,and a possible pathway for the formation of PAHs from fatty acids by thermal processing is made.3.Inhibitory effects of natural antioxidants on the formation of polycyclic aromatic hydrocarbons in fatty acid bakingThree natural antioxidants（EGCG,ferulic acid,bamboo leaf flavonoids）were mixed with methyl linolenate at 0.25mg/g,0.5mg/g,1mg/g and 2mg/g for 30min.The formation and distribution of polycyclic aromatic hydrocarbons in each group were detected by electro-baking at 240℃.The pyrolysis products of each group were detected by TG-FTIR.The results showed that:1)Three natural antioxidants（EGCG,ferulic acid and bamboo leaf flavonoids）scavenged OH free radical in vitro:EGCG>ferulic acid>bamboo leaf flavonoids,DPPH free radical scavenging rate:ferulic acid>EGCG>bamboo leaf flavonoids.There was no correlation between the scavenging rates of the two free radicals.2)The inhibition rate of natural antioxidants on PAHs formation of FAMEs increased with the increase of antioxidant concentration:at the dosage of 0.25mg/g,0.5mg/g,1mg/g and 2mg/g,the inhibition rates of EGCG on PAHs formation were-30.07%,-10.69%,11.26%and 23.31%respectively,and bamboo leaf flavonoids on PAHs formation were-30.07%,10.69%,11.26%and 23.31%respectively.The inhibition rates were 16.19%,24.70%,41.25%and 17.86%respectively.In this study,the addition of antioxidants inhibited the formation of Anl and Hen light cyclic PAHs,but did not inhibit the formation of other PAHs.3)By analyzing the infrared spectra of the pyrolysis products of methyl linolenate after adding antioxidants,it was found that compared with the control group,the absorption peaks of olefins and characteristic absorption peaks of alkanes at 3013cm^-1 and 3000cm^-1 of the pyrolysis products of FAME after adding EGCG were significantly lower than those of the control group,and the pyrolysis products of FAME after adding ferulic acid were significantly lower than those of the control group.There was no difference between the two groups.4)TG-FTIR data are consistent with PAHs production data.At 2mg/g,EGCG has stronger inhibitory effect on PAHs formation from FAME by electro-baking/pyrolysis than other two antioxidants.Ferulic acid has no obvious inhibitory effect on PAHs formation in this process.The above studies indicated that the process of natural antioxidants inhibiting the formation of PAHs from fatty acids through thermal cracking reaction may be achieved by reducing small alkenes/alkanes free radicals.