Spice extracts as dose-modifying factors in radiation inactivation of bacteria

Three spices, chili, black pepper, and turmeric, were tested for the effect of their aqueous extracts on the sensitivity of three bacteria, Escherichia coli, Bacillus megaterium, and Bacillus pumilusspores, to gamma-radiation. It was found that the extracts of the three spices offered protection to these organisms against inactivation by gamma-radiation. These spice extracts were also tested for their protection of naked plasmid DNA. Radiation-induced degradation of plasmid pUC18 DNA was reduced in the presence of the spice extracts. The maximum protection was offered by the chili extract followed by that of black pepper and turmeric. The two known antioxidants, curcumin and piperine from turmeric and black pepper, respectively, were shown to protect the plasmid DNA from the degradation by gamma-radiation. Experiments with the plasmid pUC18 DNA indicated that the spice extracts probably protected microorganisms by protecting their DNA. These studies indicated the importance of spices among ingredients in food as dose-modifying factors during radiation processing.