Studies on milk-clotting enzyme from Rhizopus sp. to manufacture

• Main Authors: Wang, Sheng-Yao, 王聖耀
• Other Authors: Lin Chin-Wen
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/61118274793210766719

碩士 === 國立臺灣大學 === 畜產學系 === 85 === This study used Rhizopus microsporus var. chinensis CCRC 31630 as starter and wheat bran as medium under the optimal condition to produce the milk-clotting enzyme. Then, this enzyme was used to prepare the milk coagulant, which was added to milk to manufacture yogurt-like product, Kou Woan Lao. We hoped that this kind of milk coagulant would be generalized to all families. As the results showed, the milk-clotting activities of crude extracts at higher incubation temperature were lower than those at lower temperature. And the effects of the quantity of water added to the medium on the milk-clotting activities were not obvious. The pH value of crude extracts increased with incubation time in spite of being in different environmental conditions. The crude extracts under the optimal incubation condition were concentrated and freeze-dried after added 25% lactose, and then this kinof milk coagulant was obtained. The high levels of proteolytic activities appeared at pH 3.0 and 6.0. Decreasing the pH value, the milk-clotting activity increased. In stabilization aspect, the proteolytic and milk-clotting activities at 30-40℃still remained, and above 1% alcohol concentration, both activities were unstable. Effects on both activities during storage for 12 weeks at 4℃and 25℃were slight. The factors that affected curdling time and curd quality when producing Kou Woan Lao were as follows: milk coagulant added, SNF content, curdling temperature, holding time after curdling, concentrations of sucrose and alcohol. Increasing milk coagulant added, SNF content, and higher curdling temperature, the curdling time decreased. Increasing concentrations of sucrose and alcohol, the flavor of products increased, but were hard to form curd. Increasing milk coagulant amount, curdling temperature, holding tns of sucrose and alcohol, the curd firmness and syneresis increased. And the microstructure of the curd revealed relatively complete and a three-dimensional spider web-like structure.