Influence of the amount of rennet, calcium chloride addition, temperature, and high-pressure treatment on the course of milk coagulation

Abstract

Coagulated gel was characterised using an oscillation rheometer Rheostress RS 150. The influence was monitored of the additions of rennet and CaCl2, of temperature, and of high-pressure treatment on the properties of coagulated gel. Parameters of coagulation were assessed, i.e. elastic modulus G’, the time of the start of coagulation t0, and the time constant of congealation τ. In monitoring the influence of increasing additions of rennet and CaCl2, and of temperature increase, it was found that the time of the start of coagulation t0 and the time constant of congealation t decreased. The limiting shear storage modulus G’max was practically constant at various amounts of CaCl2 and was moderately decreasing with increasing temperature and rennet addition. This effect was possibly caused by the fact that the limiting value is a regression parameter extrapolated to infinity. The real values of the modulus for a given time increased with increasing levels of calcium chloride added. Milk treated by the pressure of 600 MPa for 10 min formed, during coagulation, a more solid gel, the shear storage modulus being, almost by 100% higher as compared with untreated milk. Value of the time constant of congealation was practically halved.