In order to describe the kinetics of rennet coagulation, measurements
of
turbidity as a function of wavelength were used to determine the weight-average
degree of polymerization, x¯w,
during renneting of milk at three different concentrations
of enzyme and three concentrations of casein, including the normal casein
concentration of milk. The change of x¯w
as a function of time was described using Von
Smoluchowski's equation, testing a number of expressions for the aggregation
rate
constant, kij. The best description was
achieved when kij was taken as a function
of
an energy barrier against aggregation that was diminished by the proteolysis
of
κ-casein. The initial value of the energy barrier partly depended
on the casein
concentration, and had a value >25 kBT at
normal casein concentration, where kB
is Boltzmann's constant and T the absolute temperature. When
the proteolysis of
κ-casein was complete, the energy barrier was reduced to
11 kBT and was independent of casein concentration.