Comparison of mathematical models applied to the rennet coagulation of skim milks

The coagulation of renneted skim milks was monitored by dynamic measurement of elastic shear modulus (G) based on low amplitude oscillation. Four alternative time-dependency models were fitted to the measurements and compared with respect to their ability to describe the development of curd firmness and their usefulness in deriving parameters of practical interest in cheesemaking. All models described the development of G over the course of the experimental time-scale (approximate to 60 min), with the Scott-Blair and Carlson models following the experimental course of G more accurately than the other models. The fit of the Douillard model was consistent with a systematic error in the region of onset of gelation, owing to its nonsigmoidal nature, The fit of the linearized Scott Blair model was poor at the upper end of the experimental range of G. Apart from gel time as defined by G = 0.2 Pa, there was no significant difference between the Carlson and Scott Blair models & simulating most coagulation parameters, including set-to-cut time, firmness at 2.4 ks, rate of curd firming and time of maximum curd firming rate, Where significant differences occurred between the Carlson and Scott Blair models, on one hand, and either the Douillard or linearized Scott Blair model on the other, as for set-to-cut time, the mean deviations from experimental data were smaller when using the former models.