Comparative DNA-Based Detection of Irradiated Calf Liver Using FTIR Spectroscopy and Comet Assay

Developing reliable methods to accurately detect irradiated foods and verify compliance with permissible dose limits is crucial for ensuring food safety and supporting the global market for irradiation-preserved products. This study aims to investigate DNA-FTIR analysis for detecting gamma-irradiated calf liver, an animal-derived food, to accurately differentiate between various irradiation doses and, critically, to identify doses that exceed permissible safety limits. DNA-FTIR combined with scatter plot analysis of spectral band characterization parameters and hierarchical cluster analysis (HCA) was used for irradiated-sample inspections. Eighteen equal pieces from a fresh calf liver were individually sealed in polyethylene bags and frozen overnight. Next, six sets of liver slices were prepared: five for the gamma-irradiated groups (1.5, 3, 4.5, 7, and 11 kGy) and one for the non-irradiated control group (0 kGy). DNA-FTIR spectroscopy and DNA comet assays were performed for validation and comparison starting the day following irradiation. The visual assessment of the comet and its parameters indicated DNA damage in all irradiated samples, with only the tail moment parameter showing a strong linear correlation (R² = 0.9) with the administered irradiation doses. This comet parameter attained a sensitivity of 92% and an accuracy of 83% in distinguishing between irradiated and non-irradiated liver samples. The comet test failed to effectively distinguish between different doses of radiation-induced DNA damage in liver samples, and the identification of 11 kGy-irradiated samples was also inadequate. Six DNA-FTIR bands are more reliable discriminative markers for determining whether or not a liver sample was irradiated, according to scatter plots of band peak intensities and area under peak parameters. The P-O-C symmetric vibration band at 1104 cm⁻¹ demonstrated optimal discriminative accuracy and sensitivity of 100%. The characteristic parameters of different bands also showed a strong correlation with the irradiation doses (R² ≥ 0.9). Furthermore, the HCA-dendrogram allowed for a successful classification based on the homogeneity of DNA spectral characteristics. Irradiated samples at acceptable doses of 3, 4.5, and 7 kGy showed some heterogeneity in their DNAs, whereas zero kGy- and 1.5 kGy-irradiated samples showed minimal heterogeneity. Considerable spectrum heterogeneity was observed for the 11 kGy doses. Accurate classification and rapid discrimination for samples occurred between wavenumber ranges of 1720 and 1518 cm⁻¹ (reflecting the nucleobases region). Overall, it is believed that using DNA-FTIR together with HCA helps determine the irradiation history of plant and animal food products accurately and quickly, making it a practical and effective method. This could lead to significant improvements in food safety investigations.