Gamma Irradiation Effects on Carbohydrate Composition, Growth of Microorganisms and ESR Spectra of Gum Arabic ( Acacia senegal L.).

Natural gum Arabic ( Acacia senegal L.) showed appreciable growth of microorganisms in different growth media. Fungi isolated were three species of Aspergillus , Alternaria sp., Curvularia sp., and Helminthosporium sp., and dominant bacteria isolated were four species of Bacillus , Serratia marcescens and Micrococcus varians . No algal growth was observed. Gamma irradiation with ⁶⁰Co (53 Kr/h) eradicated all fungi isolated except Alternaria sp. which required 13.25 Krad irradiation and Alternaria was sp. completely eradicated with 39.75 Krad irradiation. Bacterial growth was reduced dramatically with 13.25 Krad and with 39.75 Krads of irradiation, and was completely stopped with 106 Krads. Hydrolyzed carbohydrates showed very little change, quantitatively, in both natural and irradiated gum, and paper chromatographic separation showed the presence of glucuronic acid, galactose, rhamnose and arabinose. The unirradiated gum did not show any ESR signal. The irradiated samples gave resonance lines that increased in intensity as the irradiation dose was increased. The g-value of the resonance lines was calculated as 1.004±0.001. Use of gamma irradiation as a means of irradiating microorganisms without severe damage to the carbohydrate composition, but with minor changes in the ESR spectrum of gum is discussed.