The effect of non‐thermal processing on chemical constituents and antibacterial properties of turmeric rhizome volatile oil

Abstract

AbstractThe effect of gamma irradiation under various packaging atmospheres on chemical constituents and antibacterial properties of turmeric rhizome volatile oil has been studied. The turmeric rhizome powder was packaged under different atmospheres (air, N₂, and vacuum) by high‐barrier multilayered film (Pet/EVOH–PA/LDPE) and they were gamma irradiated at dose of 5, 10, and 15 kGy. According to the results, gamma irradiation under different atmospheres of packaging did not change antibacterial properties of the volatile oil. However, oxygenated sesquiterpenes which are the major chemical constituent of the volatile oil increased by irradiation significantly by 6.45% (at 15 kGy under air packaging) (p < .05). Also, modified atmosphere packaging (MAP) was more effective to improve these active compounds, significantly (p < .05). Since gamma irradiation may cause chemical oxidation, isomerization, and hydroxylation of volatile oil's constituents, it concluded that these changes could be minimized under MAP in turmeric rhizome volatile oil, significantly.Practical applicationsIonizing radiation as a cold‐pasteurization method has widespread and growing applications in decontamination of spice and condiments but, there are lack of information or contradictory results on the effects of irradiation on chemical constituents and physicochemical properties of them. Our results showed that gamma irradiation caused quantitative not qualitative changes on chemical constituents of turmeric's volatile oil. Irradiation did not have effect on antibacterial properties of turmeric volatile oils in all doses under different packaging atmospheres. The outcome of this research demonstrated irradiation resulted in improving oxygenated sesquiterpenes contents which are the major components of turmeric volatile oil. It should be noted that irradiation under modified atmosphere (N2 and vacuum) was more effective in improving these constituents, too. Statistically, the effect of N2 and vacuum was the same but practically vacuum packaging is recommended.