بررسي پروتئوليز در ماست هاي توليد شده به وسيله سويه هاي ميكروبي بومي

Evaluation of proteolysis in yoghurts produced by native microbial strains

Yogurt proteolysis is conducted by proteolytic activity of yogurt bacteria. Proteolysis of milk proteins increases soluble nitrogen compounds and releases amino acids and peptides. In this study, native microbial strains isolated from two traditional yogurt samples (Gilan and Golpayegan) were used for yogurt production. Total nitrogen, non protein nitrogen and protein nitrogen of yogurts produced by native starters were measured. SPSS software was used for statistical analysis. Produced yogurts were stored at 4°C for three weeks. The aim of this study was to evaluate the variations of non protein nitrogen, protein nitrogen and proteolysis depth of produced yogurts during cold storage. There was a significant increase (p< 0.05) in non protein nitrogen and a significant decrease (p< 0.05) in protein nitrogen of produced yogurts during cold storage. Moreover, proteolysis depth increased significantly (p<0.05).