The effect of sterilizing doses of gamma-irradiation on the molecular weight and emulsification properties of gum arabic

Experiments were performed on raw, kibbled and spray-dried gum arabic. Microbiological tests showed that following a radiation dose of 10 kGy the contaminating micro-organisms were effectively inactivated. The average molecular weight of kibbled and spray dried gum arabic was shown by viscosity measurements to be somewhat reduced as the result of gamma-irradiation. No significant radiation-induced changes in the molecular weight of raw gum arabic could be detected. The yields of radiolytically produced strand breaks (breaks/100 eV of radiation absorbed) have been calculated for spray-dried [G(strand breaks) = 4.1 x 10(-1)] and for kibbled [G(strand breaks) = 2.9 x 10(-1)]. Gel permeation chromatography confirmed this order of radiation stability and indicated that gum arabic consists of at least three major components, the larger molecular weight fraction appearing to be the more radiation sensitive. There was no measurable change in the total hexuronic acid content (20%) of any of the samples on gamma-irradiation. Finally, measurements showed no adverse effect of gamma-irradiation, even up to doses of 30 kGy, on the ability of the gum arabic to stabilize emulsions. The extent of chemical change induced by irradiation with sterilizing doses has no practical adverse significance and demonstrates that this technique is suitable for processing raw gum arabic samples.