Abstract: The paper introduced changes of pH-value, Thorner, color, viscosity and specific weight, which were important physical qualities during different stages of process and storage of yogurt. From fresh milk to storing 192h, 11 designed points were detected in the research. The conclusion showed that the stage from inoculation to after-ripening 12h was the critical period of lactic acid raising.The viscosity and specific weight also showed evident changes toward increase during the stage. In the conditions of lower temperature 4～6℃and addition of 8%sugar, postacidification of yogurt was inhibited. The changes of color by HunterLab color analyses system

Key words: physicalquality, color, viscosity, specific weight