Technology Optimization And Application Of Rennet Casein

Optimization of rennet coagulation technology during production of rennet casein was conducted in this thesis. Rennet casein made by this technology has a good performance in making imitation cheese. The effects of different treatments to rennet coagulation on the components of rennet caseins and their performance in making imitation cheese were compared. The feasibility of different treatments to rennet coagulation in the production of rennet casein was investigated. The main conclusions were as follows:The optimized technological parameters for rennet coagulation in production of rennet casein included:rennet amount was0.78mL/L, coagulation at32℃for28min. Under this condition, rennet coagulation status was suitable for producing rennet casein with good yield and qualified components’contents.The components of rennet caseins from market and lab were approximate. Both of the rennet caseins from market and lab can be used in making imitation cheese with acceptability, even there were some difference in their pH, viscosity, texture, microstructure, meltability and rheological properties.Except that complex rennet coagulation formed a fragile curd, pre-acidification, calcium chloride-addition and both pre-acidification and calcium chloride-addition did not influence rennet coagulation status greatly. Different treatments had an extremely significant (p<0.01) influence on the moisture and ash contents of rennet casein as well as the componets and pH values of imitation cheese made of them, but no significant (p>0.05) influence on their yields, regulate yields and protein contents.Different treatments on rennet coagulation had a great impact on the hydration and emulsification satge in making imitation cheeses. Pre-acidification and calcium chloride-addition prolonged hydration of rennet casein to some extent, but the final apparent viscosity was as high as that obtained of rennet casein without treatments. Lower final apparent viscosities were obtained of rennet casein with both pre-acidification and calcium chloride-addition treatments together and with complex rennet coagulation.Calcium chloride-addition and both pre-acidification and calcium chloride-addition prolonged the time of shearing and emulsification fat droplets due to insufficient hydration in making imitation cheese. Their microstructure showed there are smaller fat globules distributed in a denser casein matrix compared to imitation cheese made of other rennet caseins. This could be the reason for imitation cheese to be harder and less meltable. Microstructure with different density, size and distribution of fat globules palyed an important role in texture, meltability and rheological properties of imitation cheese.The comparison of components and properties of imitation cheese made by rennet casein with all the treatments showed there was a linear correlation y=-376.61x+18628between the moisture content and hardness of imitation cheese with R2=0.9510, a linear correlation y=-102.71x+6870between hardness and meltalility of imitation cheese with R2=0.9907and a linear correlation y=0.0117x+18.006between G’and the hardness of imitation cheese with R=0.9616. For all the imitation cheese made of rennet casein from market and lab, there was a linear correlation y=0.0659x-0.4839between cohesiveness and protein content of imitation cheese with R2=0.9805, a linear correlation y=4.2841x-144.53between melatbility and moisture content with R2=0.952.In conclusion, rennet casein can be made by the technology obtained in this study and used in making imitation cheese with good performance. Pre-acidification and complex rennet coagulation didn’t have an enormous influence on the application of rennet casein in making imitation cheese except the yield of complex rennet coagulation was lower. Calcium chloride-addition and both pre-acidification and calcium chloride-addition treatments together made the rennet casein suitable for making hard imitation cheese. They could be used mixed with rennet casein without treatments to meet different requirements for hard, slicedable and shreddabe products. Further study should be conducted to find the relationship of rheological properties and meltability of imitation cheese made by rennet caseins with different treatments.