Nuclear magnetic resonance spectroscopy as a tool to distinguish between irradiated and non-irradiated meat

The aim of this study was to assess the usefulness of Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy i) to detect the occurrence of the irradiation marker 2-dodecylcyclobutanone (2-dDCB) in irradiated meat, as alternative to the European Standard EN 1785 method, and ii) to differentiate irradiated from non-irradiated meat by coupling spectral data with chemiometrics. 1H NMR spectra of 2-dDCB (different concentrations in CDCl3) and of the lipid fraction (50 mg in 0.8 ml of CDCl3) extracted from ground beef irradiated at 0, 2.5, 4.5 and 8 kGy were acquired on a Varian INOVA600 NMR spectrometer. Irradiation was performed using a 60Co -irradiator (1.17-1.33 MeV) on frozen vacuum-packed beef samples (25 g). The data set obtained integrating the whole spectra was statistically elaborated by multivariate analysis. The proton multiplet centred at 2.997 ppm, not overlapped by the intense signals of lipids, was used to identify 2-dDCB. The limit of detection of 2-dDCB was 50 mg/kg meat, much higher than the levels measured in beef irradiated up to 8 kGy. Discriminant analysis applied to NMR spectral data correctly classified 88.9% of originals samples according to the irradiation dose and 81.9% of cross-validated samples. In conclusion, 1H NMR spectroscopy is not suitable to detect 2-dDCB at the levels expected in beef irradiated at doses for commercial purposes. However, coupled with multivariate analysis, it may be considered a promising tool for a rapid detection of irradiated meat.