E-Beam irradiation of bagged, ready-to-eat spinach leaves (Spinacea oleracea): an engineering approach

We experimentally assessed the efficacy of electron beam irradiation to ensure the safety and quality of ready-to-eat spinach leaves using a 2-MeV Van de Graff accelerator. Spinach leaves (approximately 8 g) inside petri dishes were irradiated up to 1 kGy and stored at 4 degrees C for 15 d. Nonirradiated samples served as controls. Color, texture, vitamin C, total carotenoids, and chlorophyll content were measured using standard methods. Sensory analysis was performed by 15 untrained panelists using a 9-point hedonic scale. Color of control and irradiated samples showed slight variation throughout storage. Firmness of all samples changed significantly (P < 0.05) by half the storage time; however, exposure to radiation did not cause significant differences by the end of shelf life. Irradiation did not affect the chlorophyll and total carotenoid content, though it produced samples with significantly lower (P < 0.05) vitamin C content. For all treatments, chlorophyll content decreased by day 15 while total carotenoids remained constant. Although, by the end of refrigerated storage, all the irradiated samples received slightly lower odor scores, sensory analysis revealed that irradiation had little or no effect on the overall quality of spinach leaves. We also simulated the dose distribution within a bag of spinach leaves irradiated using a 10-MeV linear accelerator (0.3 to 1 kGy) to quantify the problem of nonuniform dose absorbed at different parts of the bag and predict death of a pathogen such as Escherichia coli O157:H7. The simulation results confirmed that it is feasible to irradiate baby spinach leaves (up to 1 kGy) to eliminate E. coli 0157:H7 while maintaining the overall quality of the produce.