Effect Of Fat On N-Nitrosamine Formation And Its Mechanismsin During Surimi Processing

In recent years,with the progress of society and rapid development of science and technology,there is growing emphasis on quality of life.Surimi product which be considered as a common aquatic product on the table,and be favored by consumers cause their simple preparation,delicate taste and rich nutrition.However,due to its high protein content,some secondary amines which could be produced by protein may react with nitrite/nitrate to produce carcinogen N-nitrosamines under certain conditions,which will bring potential safety hazards to surimi products.Therefore,research on the formation mechanism and control technology of N-nitrosamines in surimi products has become the focus of attention.Starting with the investigation of the content of N-nitrosamines in common surimi products on the market,1-2 surimi products with high content of N-nitrosamines were selected to analyze the dynamic changes of the content of N-nitrosamines in the process of processing.The main factors which affecting the formation of N-nitrosamines in surimi products were found out,and the nitrosation inhibitors of natural origin were screened by the simulated nitrification system in vitro and be applicated to surimi products.The research results are of great significance for controlling the safety of surimi products.The main research contents and results were as follows,(1)Analysis of edible quality of common surimi products on the market.The nutritional composition,physical and chemical indexes and the content of 9 kinds of N-nitrosamines in surimi products were investigated and analyzed.The results showed that the protein content of the common 10 surimi products were 8.2-18.4 g/100 g,the fat content were 0.8-12.3 g/100 g,the total sugar content were 10.0-20.4 g/100 g,the water content were 53.0%-65.5%,the content of ash were 2.2%-3.9%,the energy were 453-958 k J/100 g,the nitrite content were29.2-40.7 mg/100 g,the Na Cl content were 0.7%-1.6%,the thiobarbituric acid reaction substances(TBARs)value were 0.2-0.8 mg/kg,and the p H were 6.59-7.69.The total amount of N-nitrosamine in fish tofu was up to 39.6 ?g/kg.(2)The effect of raw materials and processing technology on the content of N-nitrosamine in fish tofu.The contents of 9 N-nitrosamines and physical-chemical indexes such as nitrite,thiobarbituric acid reaction substances(TBARs),volatile basic nitrogen(TVB-N)in raw materials and during the processing of fish tofu were determined.The resultsshowed that contents of TVB-N and nitrite in Tangguo fish tofu raw materials were decreased by 7.6 mg/100 g and mg/100 g after processing,and the content of TBARs was increased by0.8 mg/kg.Levels of NMEA and NDEA increased by 28.63 ?g/kg and 9.26 ?g/kg after adding fat during chopping process.It can be concluded that N-nitrosamines in fish tofu increased obviously when fat was added for chopping.And it was preliminarily deduced that the addition of fat may promote the formation of N-nitrosamines in fish tofu.(3)In order to evaluate the effects of fat on the level of volatile N-nitrosamines in surimi products,fish tofu with different amounts(10%,20%,30%)of emulsion pig back fat(EPBF)and emulsion skin(ESC)were manufactured respectively.The contents of volatile N-nitrosamines,their substrates(nitrites and biogenic amines),the thiobarbituric acid reaction substances(TBARs)and p H were detected at five sampling points during the processing of fish tofu.The results showed that the concentrations of nitrite first increased and then decreased along with the processing of fish tofu.The p H first decreased and then increased,while TBAR values,biogenic amine content,and N-nitrosamines content showed an increasing trend during the processing of fish tofu.On the other hand,the concentration of N-nitrosamines in fish tofu increased along with the increase of fat content.And the content of N-nitrosamines in fish tofu with EPBF was higher than that with ECS.The results showed that the type and proportion of fat can affect the formation of N-nitrosamines in fish tofu.It is preliminarily confirmed the results about(2)that fat can promote the formation of N-nitrosamines in surimi products(fish tofu).(4)Nitrosation simulation system.Vitro simulation nitrosation reaction system was used in this experiment to study the effect of oil species(peanut oil,linseed oil and sunflower seed oil)and proportion(0%-40%)on the production of NDMA and NDEA.The results showed that the three kinds of oils had a certain effect on the formation of NDMA and NDEA,and the production of N-nitrosamines in simulation system with peanut oil and linseed oil was higher than that of sunflower seed oil,and it increased with the increase of oil ratio.It is further proved that fat can promote the formation of N-nitrosamines.(5)The mechanism of fat promoting the formation of N-nitrosamines in surimi products was explored.The surimi product system was simulated in vitro,and the surimi was mixed with different oxidation degree of lard to explore the change of protein indexes and NDMA formation during storage.The results showed that the content of NDMA increased with theincrease of lipid oxidation.The content of active thiol in surimi myofibrillar protein decreased,while the carbonyl content,NDMA content and surface hydrophobicity increased with the increase of storage days.The turbidity of surimi myofibrillar protein increased first and then remained unchanged with the prolongation of storage time.It is concluded that the formation of N-nitrosamines in surimi products promoted by fat may be due to the acceleration of the oxidation of proteins in surimi products by fat oxidation,and the oxidation products of proteins may play a role in promoting the formation of NDMA.(6)Study on the intermediate of fatty acid and nitrite reaction.Fatty acids and nitrites were reacted at a certain time and temperature.The reaction product was collected and its ability to nitrosamine was observed.The results showed that the nitrite-oleic acid/Linoleic acid reactant nitrodimethylamine ability increased with the increase of fatty acid ratio in the system,with the extension of reaction time and the increase of heating temperature,the nitrite-oleic acid/Linoleic acid reactant nitrodimethylamine ability showed an enhanced trend,The addition of methyl oleate has no obvious effect on the formation of NDMA in the reaction system.Fatty acids and nitrites will produce some new volatile substances during the reaction,reaction products such as alkanes,esters,furans and other substances be produced during the reaction of Linoleic acid and nitrite.(7)The quadratic regression orthogonal design was used to study the effects of tea polyphenols,rosemary,VE,and VC on the inhibition rate of NDMA in the model system.The quadratic regression equation with four factors was obtained,tested and verified.The results showed that the quadratic regression equation could better describe the effects of the four factors on the inhibition rate of NDMA,and the theoretical highest inhibition rate was 47.16%when tea polyphenols,rosemary,VE,and VC were added at 60.14,60.11,60.00,and 60.00mg/L to the model system.The optimal combination was verified in an in vitro model system,and the average inhibition rate of NDMA was 45.32%.The inhibitors could inhabit 44.00% of NDMA in fish tofu.The results showed that regression model had high fitting degree and indicated that the optimal inhibitor combination was reasonable and feasible.