Abstract: This study aimed to optimize the formulation of milk coagulant and coagulation conditions for improved quality and productivity of milk cake (Chinese cheese) produced from fresh Holstein cow milk and milk-coagulating protease from the stems of Dregea sinensis var. corrugata using combination of one-factor-at-a-time method and response surface methodology. The results showed that the best formulation of milk coagulant consisted of the protease from Dregea sinensis var. corrugata 17.95%, citric acid 0.023 3%, and calcium chloride 0.009 85%, and the best coagulation temperature was 83.25 ℃. The sensory score of milk cake made by the optimized process was 85.7 ± 1.32, which was significantly higher than that made by the traditional acidic water method (P < 0.05). Water, crude protein and crude fat contents of our product were (52.94 ± 1.03)%, (20.09 ± 0.57)%, and (22.54 ± 0.48)%, respectively. The contents of ash, calcium, and phosphorus were increased significantly as compared with that obtained using the traditional process (P < 0.05). The contents of free amino acid and free fatty acid in milk cake obtained in this study were (77.64 ± 5.80) and (1 953.76 ± 53.53) mg/100 g, respectively. It was a good source of vitamin containing significantly contents of fat-soluble VA and VE (P < 0.05). The microstructure of milk cakes made by the traditional and new methods was different; the former showed a lamellar or cluster structure, whereas the latter presented a three-dimensional network structure. Moreover, the milk cake made by the optimized process was bright in color, having a homogeneous texture, unique flavor and plant aroma. It was a highly nutritional product with improved quality compared with that made by the traditional process.

Key words: Dregea sinensis var. corrugata, milk cake, optimized processing, free amino acid, vitamin, microstructure