Viscosity of stirred yoghurt during storage

The aim of this paper was to determine the changes in viscosity of stirred yoghurt from producer A (n = 20) and producer B (n = 20) throughout 21 days of storage. The content of fat, dry matter, non-fat dry matter, lactic acid, pH and viscosity of stirred yoghurt were determined on the 0, 7th, 14th and the 21st day of storage of the product at the temperature of 4 °C. Considerable change in viscosity of stirred yoghurt (p < 0,05) throughout the maintenance period was determined on the 0 and the 21st day for both yoghurts. The viscosity of the stirred yoghurt from producer A was increased from 0,324Pa s on the 0 day to 1,912 Pa s on the 21st day. At the same time the viscosity of the stirred yoghurt from producer B was increased from 0,208 Pa s on the 0 day to 0,883 Pa s on the 21st day. In comparison with producer A, a considerably higher quantity of non-fat dry matter and higher quantities of lactic acid (p<0,05) in the stirred yoghurt from producer B resulted in a more stable gel structure throughout the whole research period.