Removing Undesirable Color and Boosting Biological Activity in Red Beet Extracts Using Gamma Irradiation

摘要

The ethanolic extracts of red beet (Beta vulgaris L.) hairy root were used to investigate the removal of color and improvement of biological activity for better in its industrial application. The extracts were exposed to gamma-ray ranged from 2.5 to 30 kGy. The red beet hairy root is composed of two major red-colorants such as betanin and isobetanin. The gamma irradiation at 5 kGy remarkably reduced major colorants of red beet by 94% and reddish color was completely disappeared by doses greater than 10 kGy. This color removal was likely due to the effects of gamma radiolysis of ethanol. Although the details of the decay mechanism of chromophore by gamma-ray has not entirely explained, results of the present study suggest that the free radicals produced are capable of demolishing the chromophore group in all (iso)betanin, resulting in the bleaching of the substrate solution. In spite of degradation of major colorants, the biological activities such as DPPH radical scavenging and tyrosinase inhibition were negligibly affected by gamma irradiation up to 20 kGy. Antioxidant activity is retained from 92.7% in control to 90.0-92.0% in irradiated samples (2.5-20 kGy), together with slight decrease as an 87.5% at 30 kGy. In addition, tyrosinase inhibition activity has also the same pattern that is, the activity is slightly increased from 50.7% of control to 49.1-52.8% of irradiated samples (2.5-20 kGy) with a 46.8% at 30 kGy.