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.