Evaluation of physicochemical, lipolysis, proteolysis and sensory properties of concentrated " Tuluq" and Torba yoghurts during storage period

In this study, concentrated yoghurts were produced in four methods, Tuluq and Torba bags, packed in polyethylene containers and physicochemical such as pH, acidity, total solid, protein, fat and salt content, lipolysis, syneresis, proteolysis and sensory properties was evaluated with control yoghurt during 60 days storage period. In analysied samples yoghurt, pH were (3.89-4.56), acidity (0.94-1.70 g/100 g), total solid (12.5-37.5%), protein (3.7-12.5%), fat (2.9-17.9%), salt (0.2-1.3%) content and syneresis (18.5-61.5%). In the of all yoghurt samples, lipolysis increased during storage. Also, in concentrated yoghurts lipolysis was significantly (P>0.05) lower than control yoghurt during storage period. The percentage of pH 4.6-soluble nitrogen/Total nitrogen and Non-protein nitrogen/Total nitrogen in packed and control yoghurt samples increased significantly (P>0.05) during storage but in Tuluq and Torba yoghurts decreased during first 30 days and then increased significantly (P>0.05). Electrophoretic pattern showed that degradation of αs1- and β-casein were considerable in Tuluq yoghurt. This might be due to endogenous surface bacteria and yeasts activities on Tuluq bag. It was concluded that Tuluq yoghurt had high quality and long shelf-life and it is introduced as a valuable dairy product.