To develop a new Oriental-style dairy product, the characteristics of culture filtrate from lao-chao with Rhizopus oryzae, used as a milk-clotting agent, and factors (heat-treatments, calcium, sucrose, and curdling temperature) affecting curd firmness were determined. The optimal conditions for proteolytic activity were around 40 degrees C and pH 3. No activity was detected over the range of pH 8 to 11. After high-heat treatment (121 degrees C, 15 min) on skim milk, no clotting was observed. Sucrose resulted in the retardation of milk-cloning. Ca++ could be used to increase curd firmness which also increased from 29.2 +/- 2.8g to 80.3 +/- 4.7g when the curdling temperature was increased from 25 degrees C to 45 degrees C.
