Formation And Inhibition Of Heterocyclic Aromatic Amines In Deep Fried Tilapia

Tilapia,with desirable flavour and texture properties,no intramuscular spines and rich in protein and unsaturated fatty acids,is deeply loved by consumers.Deep frying is a commonly used cooking method for tilapia to obtain golden color and crisp taste,which could lead to the formation of some harmful substances(such as heterocyclic aromatic amines)due to the high processing temperature.Foodborne heterocyclic aromatic amines are a group of nitrogen-containing polycyclic aromatic compounds that form in proteinrich foods during the thermal process.When human ingest heterocyclic aromatic amines,it may cause the risk of many diseases and even cancer.Therefore,it is of great significance to study the formation and inhibition of heterocyclic aromatic amines in fried tilapia.In this study,the effects of different frying conditions and exogenous substances on the content of various heterocyclic aromatic amines(2-amino-3,4-dimethylimidazo[4,5-f] quinoline,Me IQ;2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline,Me IQx;2-amino-1-methyl-6-phenylimidazo[4,5-f] pyridine,Ph IP;9H-pyrido[3,4-b] indole,Norharman;2-amino-9H-pyrido[2,3-b] indole,A?C)were investigated.The correlations between the quality of tilapia fillets and the content of heterocyclic aromatic amines were analyzed.Finally,the inhibition mechanism of Me IQx was explored by using model systems.The specific contents and results are as follows:1.The effects of frying temperature(180 ? and 220 ?),frying time(180 ?: 2,4,6,8,10,12 min;220 ?: 2,4,6,8 min),ginger(1%,2%,3%,4%)and garlic(3%,6%,9%,12%)on the content of heterocyclic aromatic amines in fried tilapia fillets were investigated.The total amount of heterocyclic aromatic amines in 180 ? frying group(2 min-12 min),220 ? frying group(2 min-8 min),ginger adding group(180 ?;12 min: 1%,2%,3% and 4%)and garlic adding group(180 ?;12 min: 3%,6%,9% and 12%)were 0.54 ng/g-52.21 ng/g,6.33 ng/g-124.41 ng/g,9.20 ng/g-19.81 ng/g and 9.20 ng/g-16.10 ng/g,respectively.In the frying process,the higher temperature could produce more heterocyclic aromatic amines in tilapia and longer time could lead more contents of heterocyclic aromatic amines;when ginger or garlic was added to the fish fillets,the content of heterocyclic aromatic amines increased by 89.07%-115.38%(ginger)and 12.05%-75.05%(garlic),respectively.Therefore,reducing frying temperature and time can effectively reduce the generation of heterocyclic aromatic amines and ginger and garlic should be avoided to flavor tilapia in daily cooking to prevent the increase of heterocyclic aromatic amines amounts.2.The effects of black pepper(0.5%,1% and 1.5%)on the quality(moisture content,fat content,color,lipid oxidation and protein oxidation)and heterocyclic aromatic amine contents of fried tilapia fillets were studied at 180 ? for 4,8 and 12 min,respectively.The results showed that whether the frying tilapia fillets with or without black pepper,the total amounts of heterocyclic aromatic amines increased with the extension of frying time,and the contents were 6.39 ng/g-22.45 ng/g(with black pepper)and 6.95 ng/g-29.54 ng/g(without black pepper),respectively.When the tilapia samples without black pepper were fried at 180 ? for 12 min,the total amount of heterocyclic aromatic amines generated was 4.25 times as much as that of the tilapia samples fried at the same condition for 4 min,while when the frying time of the tilapia samples with 1% black pepper was extended from 4 min to 12 min(180 ?),the total amount of heterocyclic aromatic amines generated increased by 2.28 times.The effects of black pepper on the quality and heterocyclic aromatic amines content of tilapia were related to the concentration of black pepper and frying conditions.Black pepper could effectively inhibit the total amount of heterocyclic aromatic amines and the contents of Me IQx and Ph IP,but it increased the content of Norharman.When the tilapia fillets were fried at 180 ? for 12 min,adding 1% black pepper could completely inhibit the content of Me IQx and Ph IP,and the total amount of heterocyclic aromatic amines was reduced about 26.57%,while the content of Norharman was 1.42 times of the samples without black pepper.The promotion or hindrance of black pepper on heterocyclic aromatic amines in fried tilapia fillets depended on frying time and black pepper levels,as well as the formation pathway of heterocyclic aromatic amines and the types of heterocyclic aromatic amines.In addition,there are certain correlations between the quality of fried tilapia fillets and heterocyclic aromatic amines.For example,the contents of Me IQ and Norharman in tilapia fillets were positive related to the degree of protein oxidation,with correlation coefficients of 0.899 and 0.853,respectively.3.The glycine-glucose-creatinine model system was used to investigate the inhibition mechanism of pyridoxamine on Me IQx,which was easily found in aquatic products with thermal processing,by theoretical calculation and experimental verification.Firstly,by studying the effects of water-soluble vitamins(pyridoxamine,L-ascorbic acid and nicotinic acid)and phenolic acid(ferulic acid and p-coumaric acid)on Me IQx in tilapia samples and model systems,it was found that pyridoxamine had a better inhibitory effect on Me IQx.In fired tilapia cakes,the inhibition rate of pyridoxamine on Me IQx reached 78.54%,and in model system was 82.72%.At the same time,based on Maillard reaction and the formation mechanism of polar heterocyclic aromatic amines,the formation pathway of Me IQx was inferred through the reaction,and methylglyoxal was found to be an important intermediate product.Then,the influence of pyridoxamine concentration on the intermediate product methylglyoxal and the final product Me IQx was further determined by using model systems.It was found that with the amount of pyridoxamine increased from 0 mmol to 0.45 mmol,the amount of methylglyoxal in the system decreased from 25.19 mg/L to 3.26 mg/L,and the amount of Me IQx reduced about 90.50%.It was speculated that pyridoxamine would capture methylglyoxal to generate other compounds.Finally,quantum chemical calculation and mass spectrometry analysis were used to confirm that pyridoxamine can react with methylglyoxal to reduce the content of Me IQx,and the inhibition mechanism of pyridoxamine on Me IQx was proposed.The results of this study provide a theoretical basis for further study on how to inhibit the production of heterocyclic aromatic amines in thermal processing of high protein foods such as aquatic products and improve their quality and safety.