EFFECT OF ADDITION OF ?-, ?-, AND ?-CASEIN, AND Na-CASEINATE ON VISCOELASTIC PROPERTIES OF SKIM MILK CURD

Creep compliance was used to determine the effects of the addition of α-, β-, and κ-casein, and Na-caseinate on the viscoelastic properties of skim milk curd. The results of all measurements can be represented by a six-element mechanical model. Addition of α- and β-casein, and Na-caseinate (1.80g/L) to raw skim milk reduced the instantaneous modulus of rigidity and final viscosity of the curd, while κ-casein addition at the same level increased both viscoelastic parameters. Shielding of κ-casein and depletion of serum Ca++ ions by α- and β-casein is thought to have caused the reduction of curd rigidity and viscosity. Subsequent experiments indicated that the addition of β-casein before and after rennet hydrolysis produced different curd strength with the latter producing a stronger curd.