Process Biochemistry, Vol.29, No.5, 373-379, 1994
NMR Analysis and Modeling of Shrinkage and Whey Expulsion in Rennet Curd
The displacement of the curd surface after cutting and the profiles of residual water entrapped inside were monitored using one dimensional magnetic resonance imaging (MRI). Shrinkage of the curd occurred in two phases : the curd shrank immediately during cutting and then continued shrinking at a lower velocity. Experimental data of the one dimensional shrinkage of the curd obtained from the literature were simulated with a logistic equation. NMR analysis and literature data showed that the shrinkage velocity was almost constant during the initial stages. The movement of the casein strands supplies the pump work to expel whey from the curd. By applying the fundamental principles of thermodynamics and fluid flow, a simple mathematical model was used to describe simultaneous shrinkage and whey expulsion. Profiles of residual water entrapped in the curd were simulated with this model to confirm its validity.