Improved Electron Spin Resonance Spectroscopy with Different Sample Treatments to Identify Irradiated Sprout Seeds

Irradiation helps to reduce microbial load in sprout seeds and prevents the outbreak of sprout-related foodborne illness. In food materials of plant origins, irradiation produces free radicals in cellulose and crystalline sugars which could serve as irradiation detection markers in electron spin resonance (ESR) analysis. In the present research, radiation-induced free radicals were studied in the seeds of alfalfa and broccoli irradiated at 0, 2, 4, and 6 kGy. The effect of three different sample pretreatments, namely freeze-drying, alcoholic extraction, and nitric acid extraction (5, 10, and 15 %), was also investigated. Freeze-dried and alcoholic-extracted samples lacked radiation-induced ESR spectral characteristics. However, the sample treatment with 5 % nitric acid was found most appropriate to obtain clear evidence of irradiation. These findings indicate the possible need for different sample pretreatments for clear or improved ESR spectral features.