The kinetics of milk coagulation: IV. The kinetics of the gel‐firming process

Abstract

A mechanistic kinetic model of gel firmness development during milk gel formation is presented. The model correctly accounts for the influence of enzymatic kappa-casein hydrolysis on the rate of firmness development in renneted milk gels. The model used is based on two first-order reactions occurring in series. The first reaction is enzymatically controlled and corresponds to the formation of gel crosslink sites by kappa-casein hydrolysis. The second reaction is nonenzymatic and corresponds to the process of crosslink formation and depletion of active sites. The model successfully predicts gel firmness development in the temperature range 31-45 degrees C for a variety of initial enzyme concentrations.

Kinetics of milk coagulation: III. Mathematical modeling of the kinetics of curd formation following enzymatic hydrolysis of κ‐casein—parameter estimation

“…* Throughout this paper the term "kinetics of milk coagulation" will be used to refer to the (observed) rate at which visible precipitates (flocs) or gels of casein protein form in fluid milk. coagulation time, t,, and the amount of enzyme used in the reaction, Eo, was a constant for a given milk sample at a given pH and temperature, i.e., t,Eo = c (1) It was observed that the value of the constant, c, depended on the pH, temperature, and source and composition of the particular milk sample. This simple model has often been used as a basis for comparing the activities of enzymes and for standardizing enzyme solution~.~~ ' Unfortunately, there are many experimental conditions under which eq.…”

A study on bovine kappa-casein aggregation after the enzymatic action of chymosin

“…The step of the p--CN aggregation starts when 60-85% of the surface -CN has been proteolyzed by the enzymatic action exerted by the chymosin, the enzymatic rennet component that is able to act specifically on -CN at the time the enzymatic hydrolysis was produced in our working conditions [37]. Therefore, this step is usually overlapped with the end of the first one.…”

“…The standard Hansen's liquid rennet was a gift of COTAR S.A. (Argentine, Rosario) with a milk-clotting activity of 0.03 RU, where 1 RU is the required activity for rennet in 100 s 10 mL of dried milk suspension reconstituted in 10 mM CaCl 2 at no adjusted pH (approximately 6.4) and in IDF standard 110A:1987 specified conditions. Under conditions of rennet excess, the p--CN aggregation kinetics can be studied by estimating the initial rate of doublet formation, as proposed by Smoluchowski for Brownian aggregation [37], from the measurement ofˇchanges as a function of time. Three millilitre samples of 0.04% of -CN samples in 10 mM Tris-HCl, 10 mM CaCl 2 , at pH 6.4 were poured into spectrophotometer cuvettes in a jacketed cuvette holder maintained at 35 • C by water circulation, in a diode array Spekol 1200 spectrophotometer.…”

Kinetics of rennet casein gelation at different cooling rates

“…Rheology, on the other hand, provides an alternative approach to studying structure formation. Using a strain within the linear viscoelastic regime (LVR), the structure development during a process can be monitored by a rheometer, and a wealth of information has been reported on rheological data to illustrate the kinetics of network formation [7][8][9][10][11][12][13].…”