Identification of irradiated meats by determining o- and m-tyrosine as markers

To identify the irradiated meats, various parameters that affect extraction efficiency of tyrosine positional isomers were evaluated. The optimum procedure employed simple extraction by 0.1% formic acid and protein precipitation by acetone. Baseline separation for the extract was carried out on LC-fluorescence detection (FLD) and LC-tandem mass spectrometry (MS/MS). The LC-FLD and LC-MS/MS method had LOD of 1.7-2.1 and 0.3-0.5 ng/mL, respectively, and showed excellent linear correlation over three orders of magnitude, obtained ideal recoveries (78.68-88.90%) and RSD (≤ 8%). The methods were successfully applied in multiple samples. For o- and m-tyrosine, the order of descending trend was: chicken>beef > hairtail > pork and chicken > hairtail > beef > pork, respectively. The radiation dose could be quantitatively evaluated by the nonlinear correlation (y = A(0) x (2) + A(1)x + A(2)) with coefficients of determination r(2) > 0.998 in individual meat samples.