Tehran University of Medical Sciences Journal of Food Safety and Hygiene 2476-3241 8 1 2022 07 07 42 52 Samira Hosseini Department of Food Science and Technology, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Science, Tabriz, Iran, Aziz Homayouni-Rad Department of Food Science and Technology, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran Hossein Samadi Kafil Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Nazli Dorud Department of Food Science and Technology, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran 2022 04 26 2022 06 23 The antimicrobial effect postbiotic extant of Lactobacillus casei was evaluated against Escherichia coli by well propagation method and growth inhibition zone diameter was measured. The selected concentration of the postbiotic extract of L. casei was added to milk containing E. coli, followed by evaluating the changes in colony number and pH during storage (1 and 5) days at 4°C then compared with control milk. The largest growth inhibition zone was formed at a concentration of 800 µl/ml against E. coli. Also, the counts of E. coli decreased on days 1 and 5 in the evaluated milk containing postbiotic (p≤ 0.05). The pH of milk containing postbiotic was 6.5-6.8 (p≤ 0.05). The results showed that the postbiotics of L. casei inhibited the growth of E. coli in milk containing. https://jfsh.tums.ac.ir/index.php/jfsh/article/view/373 https://jfsh.tums.ac.ir/index.php/jfsh/article/download/373/186