Quality Evaluation of New Developed Symbiotic Yogurt over the Storage at Refrigerator

Document Type: Research Paper


Assistant Professor of the Department of Food Science and Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran.


Two probiotic bacteria (Lb. acidophilus and B. lactis) were immobilized on the alginate coat of strawberry pieces and were added to the prepared sweet non fat dietary stirred yogurt. Physico-chemical parameters namely pH value, titratable acidity and synersis along with the viability of probiotic bacteria of the samples were evaluated over the 8 days of storage at 5 ºC at 2 day intervals. A significant decrease in pH value occurred after 6 and 8 days and the titratable acidity significantly increased after 8 days. Synersis did not show significant changes probably due to the presence of applied hygroscopic nature of some ingredients in the samples. Some free probiotic cells were identified in yogurt matrix of the samples due to the migration phenomenon. The decrease trend of embedded cells happened slower than the free ones. This might be due to the protective effects of alginate coat on the survival of probiotic bacteria surrounded by yogurt.


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