en Food Science Food Science پژوهشي Research <strong>Background and Objectives: </strong>The aim of the present study was to investigate effects of incorporating Iranian native and commercial probiotic strains (<em>Lactobacillus acidophilus</em>, <em>Lactobacillus casei </em>and <em>Bifidobacterium lactis</em>) on the rheological and syneresis properties of yogurts.<br> <strong>Materials and Methods: </strong>Samples were heated (90 &deg;C, 15 min) after reconstituting in milk (13% SNF). After cooling down, the starter culture and probiotics were incorporated. Incubation was carried out at 42 &deg;C until the pH decreased to 4.5. Syneresis was assessed based on Amatayakul <em>et al</em>. method. Rheological characteristics were assessed using dynamic oscillation (strain sweep and frequency sweep) and rotation assays.<br> <strong>Results: </strong>Results revealed significant improvement in characteristics of the probiotic yogurts, compared to the control sample. Based on the results of rheological assessments, yogurts showed viscoelastic behaviors. In general, yogurts containing the native strain of <em>L. acidophilus</em> provided further desirable rheological and syneresis characteristics.<br> <strong>Conclusions: </strong>Therefore, it is strongly recommended to use native Iranian <em>L. acidophilus</em> in probiotic yogurt production. Bifidobacterium, Lactobacillus, Yogurt, Rheological characteristics 37 44 http://nfsr.sbmu.ac.ir/browse.php?a_code=A-10-960-1&slc_lang=en&sid=1 Somayeh Heydari somaieh_heidary_m@yahoo.com 10031947532846005391 10031947532846005391 No PhD student Department of Food Science and Technology, Faculty of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran. Seyed Ebrahim Hosseini ebhoseini@srbiau.ac.ir 10031947532846005392 10031947532846005392 No Department of Food Science and Technology, Faculty of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran. Amir M. Mortazavian mortazvn@sbmu.ac.ir 10031947532846005393 10031947532846005393 Yes Food Safety Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Salman Taheri taheri@ccerci.ac.ir 10031947532846005394 10031947532846005394 No Chemistry and Chemical Engineering Research Center of Iran, Tehran, Iran.