Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 6 1 2014 02 15 51 58 Hamidreza Alighourchi Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. Mohsen Barzegar Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. Mohammad Ali Sahari Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. Soleiman Abbasi Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. 2015 10 16 Background and Objectives: Pomegranate fruit is a rich source of bioactive compounds. The serious concern over unprocessed fruit juices is microbial contamination, which effectively inactivated by thermal processing, but it significantly affects juice functional compounds. Therefore, the effect of gamma irradiation and ultrasonic on inoculated microbial to pomegranate juices was studied. Materials and Methods: Two pomegranate cultivars were purchased from the Agricultural Research Center of Saveh, and their juices were extracted by a manual device and immediately centrifuged. Then the studied microorganisms were resuspended in sterile pomegranate juices. The juices were continuously sonicated at amplitude levels of 50, 75 and 100% and times of 0, 3, 6, 9, 12 and 15 min at temperature of 25 ± 1°C. Irradiation treatment was also carried out at various doses of 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3 kGy. Results: The results showed that lower amplitude levels (50 and 75%) did not inactivate E. coli and S. cerevisiae significantly (<1.5 log reduction), while at 100% amplitude level for 15 min, their population reduced by 3.47 and 1.86 log cfu/mL, respectively. Gamma irradiation treatment at 1 kGy also reduced E. coli by 6.66 log cfu/mL, whereas at 3 kGy it reduced S. cerevisiae by 5.08 log cfu/mL. Conclusions: The low-dose gamma irradiation could potentially inactivate the studied microorganisms compared to the sonication, which had less destructive effects on their populations. Further research is needed to determine the effect of these methods on other fruit juices for industry purposes. https://ijm.tums.ac.ir/index.php/ijm/article/view/458 https://ijm.tums.ac.ir/index.php/ijm/article/download/458/234