Cheese の粘弾性と水分効果

抄録

Process cheese is an emulsion in a solid state consisting of protein denatured by enzyme, milk fat dispersed in the form of small particles and water containing salt.
In this experiment, a variation of viscoelastic property of process cheese with various moisture content and temperature was measured by means of three kinds of rheometer, i.e. a cone-plate viscometer, a compression tester and a dynamic viscoelastometer.
The static viscosity η measured by the cone-plate viscometer decreased logarithmically with increase of moisture content in the range from 35 to 42 percent and the activation energy ranging from 8.6 to 8.3Kcal/mol.
On the other hand, the elasticity and internal friction changed from 7×10⁶ to 2×10⁶ dyne/cm² and from 0.65 to 0.80 at 20°C respectively with the variation of moisture content.
When the compression-recovery cycles were repeated on the specimen, the elasticity of cheese increased gradually and reached a plateau region. Consequently, the process cheese has rheologically the behaviour of work hardening.
The dynamic viscoelasticity of casein networks in cheese texture with change of moisture content ranging from 36 to 42 percent was obtained; dynamic viscosity η_d=(1.8∼2)×10⁴ poise and dynamic elasticity E'=(8∼6.4)×10⁶ dyne/cm² respectively.
These values also change with the temperature of storage after processing of cheese.
Process cheese becomes harder by storage at lower temperature in the lower content of moisture. From the X-ray diffraction analysis of process cheese and paracasein, it was found that the variation of elasticity with moisture content was attributed to the change of network structure formed by casein micelles.