Hiba Zedan - Department of Microbiology and Microbial Biotechnology, Faculty of Life Science and Biotechnology, Shahid Beheshti University, Tehran, Iran
Seyed Masoud Hosseini - Department of Microbiology and Microbial Biotechnology, Faculty of Life Science and Biotechnology, Shahid Beheshti University, Tehran, Iran
Ali Mohammadi - Department of Microbiology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran

Background and Aim : The aim of this study was to investigate the effect of different concentrations from three types of chitosan on sensory and long-lasting properties of yogurt, By investigating physical-chemical properties (such as pH, acidity percentage, Syneresis, percentage of dry matter, fat and protein), Microbial( The effect of chitosan on the growth and activity of yogurt starting bacteria, mold and yeast, coliforms, Escherichia coli in yogurt.Methods : different chitosan with different concentrations were added to yogurt, Various treatments maintained in three weeks Physical-chemical and microbial evaluations at two temperatures in the refrigerator and room were performed.Results : The effect of different concentrations of chitosan on protein content of yogurt samples was insignificant (۰.۰۵ < p) and on the dry matter content of yogurt fats was significant (۰.۰۵ > p). The effect of temperature and shelf life on the amount of dry matter, fat and protein was not significant (۰.۰۵ < p), Chitosan concentration, temperature and shelf life , On pH, acidity, dry matter, fat, Syneresis as well as starting bacteria counting and yeasts, have a significant effect (۰.۰۵ > p).Conclusion : The use of chitosan increases the pH and reduces the acidity and Syneresis, Especially in refrigerated samples. The use of chitosan has reduced the number of starting bacteria and yeast . The count of mold, coliforms, and Escherichia coli was zero in all samples, Yogurt samples with high concentrations of chitosan have the highest score, While samples with low concentrations of chitosan ,The highest sensory score were Allocated.

chitosan, yogurt, durability, physical-chemical and microbial properties