Ethanol extraction-based drying enhanced ESR radical detection in oranges irradiated to different ionizing radiations during storage

• Oven drying after ethanol extraction improved ESR detection of irradiated orange.
• Radiation-induced triplet signal was detected regardless of radiation sources.
• Enhancement of signal sensitivity has been correlated to dietary fiber content.
• Successful identification has been established after storage in various conditions.

The detection of cellulose radicals by ESR spectroscopy in oranges irradiated by different radiation sources has been studied during storage. The peel of oranges was found to be more suitable for ESR analysis in comparison with flesh parts because of its higher fiber and lower moisture contents. The oranges were exposed to gamma ray, electron-beam, and X-ray sources, and the paramagnetic centres were investigated. The samples extracted with absolute ethanol followed by oven drying showed a reduced drying time (five-fold) and enhanced signal sensitivity (double) in comparison to freeze dried samples. Further, the ESR spectrum showed that a radiation-induced signal could be detected in samples exposed to a dose above 0.4 kGy regardless of the radiation source. Irradiated oranges were stored at different conditions such as dark at 4 °C, fluorescent light at 20 °C, and indirect natural light, to study ESR spectral behavior. Fading of signal intensity was predominant when the samples were stored under natural and artificial light. The identification of cellulose radicals using ESR technique was improved for irradiated oranges containing a total fiber content of more than 60% (dry basis) after ethanol extraction even after a prolonged storage.