抄録
The static viscoelasticity and consistency of several processed and natural cheese (Gouda and Cheddar) were measured by means of four kinds of rheometer or consistometer, i.e. parallel plate viscoelastometer, cone-penetrometer, micro-penetrometer and sectilometer.
From the analysis of the results by means of the four-element mechanical model, we obtained the instantaneous elasticity (E1), retarded viscosity and elasticity (η2, E2), flow viscosity (η3) and retardation time τ for cheese, respectively. The viscosity of cheese ranged from 107 to 108 poises, the shear rigidity ranged from 105 to 106dynes/cm2 and the retardation time ranged from 200 to 500sec, at room temperature.
In the cases of viscoelastometer by shear creep and micro-penetration method, both the logarithmic relation between the creep compliance J (t) and the time scale t could be reduced to a master creep curve by the shift along the axis of time scale at the temperature ranging from 5 to 45°C. It is seen, therefore, that the cheese has the behavior of rubbery elasticity and is thermorheologically simple in the narrow range of temperature.
The yield value can be obtained for the same cheese by using a cone-penetrometer which has cones of various angle and weights. The yield value of cheese is about 2×105dynes/cm2 at 29°C and is constant independent of cone angle or weights. Cone-penetrometer and sectilometer can not measure the elastic constant, but are useful for measurements of consistency of cheese. Under a certain condition of measurement, both the logarithmic plots of the degree of sectility Ps and micro-penetration Pm are represented by a straight line.
