Manganese Free Radicals in Cobalt-60 Gamma-irradiated Strawberries

Abstract

THE formation of free radicals in biological systems exposed to ionizing radiation is well established^1–7. Some of the induced radicals, as well as some of those occurring naturally⁸, have long lives^9–11. The surprising stability of the induced radicals may have far-reaching biological implications. As an example of stability, cystine, on irradiation in vacuo at room temperature, gave electron paramagnetic resonance signals even after 35 days¹². Numerous investigations in connexion with irradiation damage of proteins and amino-acids confirm the stability of these radicals^13–18. This stability must be considered carefully in assessing the wholesomeness of foods preserved by ionizing radiation. Such assessment involves the concepts of stored chemical energy and consequent radio-mimetic hazard^19–20. Chromosomal aberrations have been shown to occur in germinating barley and onion seeds following treatment with orange or apple juice, which had been irradiated with 200 Krad of γ-rays²¹. Although the radiomimetic precursors generated by irradiation of fruit juices have not been ascertained, preliminary studies indicate that peroxides may be implicated.