| Food irradiation, as a kind of cold processing technology, is widely used in food industry. While, it is urgent desire to establish effective supervision and guarantee healthy development of food irradiation for consumes. Recently, the detection methods of food irradiation are established for gamma ray irradiation, and mostly focused on spices, poultry, nuts and other products. While, researches related to irradiated aquatic products are few. As the development of electron beam irradiation and comprehensive use in aquatic products, to establish and improve the testing method of electron beam seafood is extremely urgentThe detection techniques continue to develop according to the radiation induced changes on lipid, protein, DNA and carbohydrate composition by researches. And ortho-tyrosine is used as a marker to detect irradiated food, which is formed by the reaction between radiolytically produced hydroxyl radicals and aromatic ring of phenylalanine-containing proteins in food, and often applied to higher protein products. As little reports on the detection of aquatic food by electron beam irradiation, the correlation between radiation dose and o-tyrosine is unclear. The study is established a reversed phase high performance liquid chromatography to detect the content of o-tyrosine in aquatic products, the change of o-tyrosine content during processing and storage, in order to study the correlation between o-tyrosine content and radiation dose. Furthermore, phenylalanine is to detect by HPLC after irradiation to analysis conversion rate of o-tyrosine, all of these is to support for the detection of radiated aquatic food and ensure consumers’ health. Research finds that:The detection method by HPLC of free ortho-tyros ine was established. Ortho-tyrosine was separated within 12min using Aglient Eclipse-C18 column with 0.1% formic acid and methanol as mobile phase, the fluorescence detection wavelength at 275nm and 305nm, flow rate at 0.8mL/min, and column temperature at 30℃.The validation results shows that the linearity of o-tyrosine ranges from 1 to 10000 μg/L(R2=0.9998), detection limit is 2.7μg/mL. The RSD value of Metapenaeus ensis. Lateolabrax japonicas, Scallop are 3.141,2.350,1.549 respectively. This HPLC method was satisfied with the determination of o-tyrosine contents in seafood. For the content of dissociative o-tyrosine in some seafood, the order of descending trend was:Metapenaeus ensis>Lateolabrax japonicas>Scallop.1) Ortho-tyro sine content did not change significantly in irradiated aquatic food with processing and storage. Researches are focused on the influence of o-tyrosine content with different processing and storage conditions, there were fluctuations of o-tyrosine content, however, no significant change in edible state. And especially for storage at -20℃, little change of o-tyrosine was found.2) And the correlation between o-tyrosine content and irradiation dose can be quantitatively evaluated by the following nonlinear correlation within 0-10kGy dose rate:for Lateolabrax japonicas, Y=0.1133X3-0.3534X2+5.2943X-1.1651.R2= 0.9986;for Metapenaeus ensis, Y=-0.5626X3+10.206X2-4.9731X+6.8588,R2= 0.9938;for Scallop, Y=0.1376X3-2.7062X2+19.949X+2.3847,R2=0.985.The results showed that different kinds of products had different conversion of o-tyrosine.3) Further study was done for the conversion of phenylalanine to o-tyrosine at different irradiated dose, o-tyrosine had the conversion of 0.019%-0.105% at 1-10kGy dose, much more higher than the presence of sample matrix. It was explained that matrix influenced the transformation of o-tyrosine, and different kind of seafood had different conversion.In conclusion, for the focus of irradiated food supervision, the detection method of o-tyrosine by HPLC was established. And the influence of o-tyrosine content during processing and storage was analyzed. Furthermore, the relationship between irradiation dose and the content of o-tyrosine was established. All of these were contributed to the detection of irradiated food and the protection of consumers’ health. |
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