| Summary: | 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.
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