Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 3 2025 06 02 420 433 Sara Jafarirad Department of Food Science and Technology, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran Leila Nateghi Department of Food Science and Technology, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran Masoumeh Moslemi Halal Research Center of IRI, Iran Food and Drug Administration, Ministry of Health and Medical Education, Tehran, Iran Kian Pahlevan Afshari Department of Animal Science, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran Ali Ahmadi Hassan Abad Department of Food Science and Technology, Faculty of Agriculture, Shiraz University, Shiraz, Iran Kianoush Khosravi-Darani Department of Food Technology Research, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2024 08 04 2025 05 27 Background and Objectives: Probiotic yogurts enriched with Lactobacillus paracasei (L. paracasei), protein hydrolysates derived from Sargassum angustifolium macroalgae (SAPH), and encapsulated SAPH were formulated to inhibit Streptococcus mutans (S. mutans), the primary bacterium responsible for dental caries. Materials and Methods: The yogurt samples were evaluated for physicochemical, microbiological, and sensory characteristics. Results: On day 21, the yogurt supplemented with L. paracasei demonstrated the greatest titratable acidity (97.35°D), the lowest pH value (4.24), reduced syneresis, and enhanced antioxidant, antihypertensive, and rheological properties. In terms of antibacterial activity, the lowest S. mutans count was detected in formulations containing free SAPH, either alone or in combination with L. paracasei. Conversely, yogurts formulated with encapsulated SAPH exhibited higher survival rates of both L. paracasei and S. mutans compared to those containing the free form of SAPH. Conclusion: The findings indicated that although the probiotic yogurt containing free SAPH was more effective in reducing S. mutans levels within the yogurt matrix, the encapsulated form achieved an acceptable level of antibacterial activity while contributing to improved sensory acceptance. https://ijm.tums.ac.ir/index.php/ijm/article/view/4967 https://ijm.tums.ac.ir/index.php/ijm/article/download/4967/1784