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Evolution of the Levels of Free Radicals Generated on Wheat Flour and Wheat Bran by Electron Beam

¹National Institute for Lasers, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomistilor St., P.O. Box MG-36, 077125, Bucharest-Măgurele, Romania. ²Corresponding author. Phone: +40-21-457-45-07. Fax: +40-21-457-42-43. E-mail: monica.nemtanu@inflpr.ro ³National Institute of Materials Physics, 105 bis Atomistilor St., 077125 Bucharest-Măgurele, Romania.

This paper presents the experimental data regarding the levels of free radicals investigated by electron spin resonance (ESR) on wheat flour and wheat bran exposed to an electron beam. Samples were irradiated with an electron linear accelerator of 6 MeV and then stored at room temperature in air. ESR spectra of the samples indicated presence of free radicals induced by electron beam. Three types of free radicals have been detected in wheat flour, and signals typical for cellulose-like radicals have been noticed for wheat bran, their concentration increasing with the irradiation dose. The postirradiation storage of both sample types caused radical decay with a two-step pattern associated with fast decay of short-life radicals followed by slow reduction of long-life radicals. However, in the first step, the irradiated wheat bran exhibited more rapid decay of radicals than irradiated flour owing to their different complex matrixes, which led to paramagnetic structures of different origin after exposure to an electron beam. The ESR technique allows the detection of free radicals induced in wheat flour and bran by electron beam for a limited period after irradiation that could be shorter than the shelf life of the products.