Abstract: The effect of different pasteurization time-temperature conditions (A1: 60－70 ℃, 30 min; A2: 70－80 ℃, 20 min; A3: 80－90 ℃, 15 min; A4: 90－95 ℃, 10 min; A5: 95－100 ℃, 5 min; and A6: 121－130 ℃, 10 s) on the quality of freshly processed yogurt and its samples after storage at 4 ℃ was studied based on viscosity, hardness, whey separation, pH and sensory evaluation. The results showed that the thermal sterilization of raw milk at temperatures higher than 80 ℃ for more than 5 min could improve the viscosity and the hardness of yogurt, reduce its whey separation, and stabilize its texture, pH and sensory characteristics during storage. The samples resulting from A3 and A4 treatments displayed higher viscosity and hardness, lower syneresis rate and better mouth feeling and flavor, and their texture and flavor could be maintained better during 4 ℃ storage.

Key words: pasteurization, viscosity, hardness, whey separation, yogurt