Résumé
Tuluq and Torba yoghurts are traditional concentrates from Iran. Physicochemical, nutritional, and sensory properties of these yoghurts were studied along 60 days of storage. Results showed that, both pH and percentage of free whey decreased significantly (P < 0.05), while titratable acidity, total solid, salt, protein and fat content increased (P < 0.05) during storage. The yoghurt lipolysis decreased during the first 30 days and then increased during the storage. The indexes pH 4.6-soluble nitrogen/total nitrogen and non-protein nitrogen/total nitrogen in yoghurt samples decreased during first 30 days, possibly due to removing of low molecular weight nitrogenous compounds of Tuluq and Torba bags at late storage and then increased. Considerable αs1-and β-casein degradation occurred in Tuluq yoghurt. This might be due to endogenous surface bacteria and yeasts activities on Tuluq bag. It was concluded that Tuluq yoghurt had long shelf-life and high quality, being a valuable dairy product.