Effect of gamma irradiation on the antioxidant and antimicrobial activities of cinnnamon powder

Spices and herbs have been added to foodstuffs since old times due to their medicinal، preservative and flavouring effects. They are، however، often contaminated with microorganisms. Gamma irradiation is currently used widely to eliminate microbial contaminations in foods. The aim of the study was to determine the effects of gamma irradiation on the antioxidant and antimicrobial activities of cinnamon (Cinnamomum zeylanicum).

Samples of cinnamon were exposed to gamma irradiation at doses of 10، 15، 20 and 25 kGy، followed by preparing hydroalcoholic (50% ethanol) extracts from them for sequence analysis. The antioxidant activity of the irradiated and control samples was measured by DPPH radical scavenging، ferric reducing power، and bleaching of beta-caroten، and the total phenolic content was also determined. The broth diluting method was applied for the determination of minimal inhibitory concentration (MIC) of E. coli and S. aureus. All tests were performed in triplicates، and the least significant difference (LSD) statistical test at α = 0. 01 was used to compare differences among the means.

Gamma irradiation had no adverse effects on antioxidant activities and total phenolic content of the samples. Only at doses more than 10 kGy did the radical scavenging activity of the cinnamon extract increase (DPPH test). With regard to the effect of gamma irradiation on antimicrobial activity، as compared to the control value، there was no statistically significant difference in the activity of irradiated samples up to a dose of 25 kGy.

Gamma irradiation treatment of cinnamon had no adverse effect on its antioxidant and antimicrobial activities. Gamma irradiation at doses up to 25 kGy seems to be appropriate for cinnamon.