Nonfat dry milk was dispersed in .01 M
CaCI2 (12 g + 100 ml) and equilibrated overnight
at 4°C. Thirty minutes before addition
of enzyme, 3 ml of the substrate were placed in
a 1-cm pathlength cuvette in a Beckman DU-8B
UV/Vis spectrophotometer and heated to and
maintained at 35°C. The spectrophotometer
absorbance reading then was set to zero. A slit
width of 1 nm was used. An ion exchange
purified chymosin solution (New Zealand
Cooperative Rennet Co. Ltd., Eltham, New
Zealand) of sufficient activity to give a Formagraph
3 coagulation time (15) of approximately
6 min (or as required) then was added (10/~1).
The reaction mixture was stirred rapidly (