RESUMO
A rapid and reliable method for determining irradiation histories of ground beef and prawns was developed on the basis of a method for determining the irradiation history of beef liver by liquid chromatography-tandem mass spectrometry (LC-MS/MS) of 5,6-dihydrothymidine (DHdThd). Improvements in the method included the following: (1) 50% ethanol precipitation in the DNA extraction step was conducted before the RNase step, (2) snake venom phosphodiesterase I was used for DNA digestion to boost liberation of DHdThd, and (3) a matrix-matched calibration curve was used for determining DHdThd by LC-MS/MS analysis. This method successfully determined irradiation histories of ground beef and prawns. Furthermore, a close correlation between the formation of DHdThd and 2-alkylcyclobutanones, which are an established index of irradiation histories, was observed in ground beef. DHdThd in DNA could be a promising candidate for a new index of irradiation histories of various foods.
Assuntos
Cromatografia Líquida/métodos , Decápodes/química , Carne/análise , Frutos do Mar/análise , Espectrometria de Massas em Tandem/métodos , Timidina/análogos & derivados , Animais , Bovinos , Decápodes/efeitos da radiação , Irradiação de Alimentos , Carne/efeitos da radiação , Frutos do Mar/efeitos da radiação , Timidina/análiseRESUMO
A method for detecting irradiation histories of raw beef livers was developed by measuring 5,6-dihydrothymidine (DHdThd) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Liver DNA was extracted using phenol-chloroform extraction followed by precipitation in 50% ethanol. DNA was then enzymatically digested and nucleosides were purified using an OASIS MCX column. DHdThd and thymidine (dThd) contents of resulting test solutions were analyzed using LC-MS/MS. DHdThd was detected specifically after γ-irradiation. Concentration ratios of DHdThd to dThd in the test solutions increased dose-dependently after irradiation at 1.0-11.3kGy, which included the practical dose for sterilization of 2-7kGy. Dose-response curves from beef livers of individual animals almost overlapped. Thus, this method is a candidate for the detection of irradiation histories of foods from which DNA can be extracted.