Physico-chemical properties and antioxidant activities of extracted essential oils from irradiated rosemary and clove buds

Abstract Dried rosemary leaves (Rosmarinus officinalis Lamiaceae), and dried clove buds (Syzygium aromaticum) were irradiated with γ-irradiation by Cobalt-60 as an irradiation source at different doses (0, 5, 10, 15, 20, 25 and 30kGy) as an effective method for sterilization, pasteurization and food decontamination, considered as safe method , and stored for 12months at room temperature (22±3 0C). The evaluation of irradiation depended on the chemical studies and antioxidant activity of extracted essential oils. Results showed significant difference for the essential oils yield (content %) at different doses during storage time. Compounds were fractionated and identified by GC/MS for extracted essential oils from each of non – irradiated and irradiated dried rosemary leaves and dried clove buds samples, the main components of essential oil extracted from either non-irradiated or irradiated rosemary leaves were 1,8 cineole, camphor and γ-pinene 26.36, 12.63 and 16.98%, respectively, while, eugenol was the major component in clove essential oil (which extracted from non-irradiated and irradiated samples (81.69%). No differences were noticed in the % of essential oils constituents. Antioxidant activity as % of DPPH scavenging increased with the increasing of essential oils concentrations (250 up to 2500ppm). Furthermore, the effect of adding these extracted oils from non-irradiated and irradiated samples as well as their mixture (1:1) on the threshold odor scores of sunflower oil (Mean of acceptable odor levels) was observed. Rancimat test shown the high oxidative stability in sunflower oil supplemented with 0.3% clove essential oil which extracted from 15kGy irradiated sample was 11.99 hrs, its relative stability was 144.11% comparing with the oxidative stability of sunflower oil supplemented with 0.5% rosemary essential oil extracted from non-irradiated sample (9.76hrs) with 117.3% relative stability. Adding different concentrations of rosemary, clove buds essential oils which extracted from different irradiation doses samples and their mixture (1:1) caused slightly increasing in oxidative stability of sunflower oil.