The application of different detection methods for irradiated dried anchovy and shrimp

Three different techniques, photostimulated luminescence (PSL), electron spin resonance (ESR) and thermoluminescence (TL) were applied for the detection of dried anchovy and shrimp exposed to electron beam at 0–10 kGy. PSL values for irradiated samples were more than 5000 photon counts/60 s, upper threshold (T₂), whereas those of non-irradiated samples were <700 counts (lower threshold, T₁) in anchovy and intermediate values of T₁–T₂ in shrimp. ESR measurements using both the whole samples did not show any signals specific to irradiation. However, in the case of anchovy it was possible to use bone for ESR detection, showing typical signals (g=2.002, 1.998). Minerals separated from both the samples for TL measurement showed that non-irradiated samples were characterised by glow curves situated at about 300°C with low intensity, while all irradiated samples showed glow peaked at about 200°C and its intensity was high enough to be discriminated from the non-irradiated ones. Furthermore, normalization by a re-irradiation enhanced the reliability of detection results of TL. In conclusion, a multi-step detection using different methods enhances confidence in the detection of irradiated food.