Abstract
A new method of analyzing the viscoelastic behavior of liquid food materials is proposed. This new analysis method is based on a non-rotational concentric cylinder (NRCC) method that simultaneously measures the static viscoelastic properties (viscosity and elastic modulus) at a constant shear rate. Mayonnaise and ketchup with or without added water were used as the liquid samples. Two-element models, i.e. a series model comprised of a Newtonian viscous element and a Hookean elastic element (Maxwell model) and a parallel model comprised of these same two elements (Voigt model), were investigated in this study to elucidate the possibility of predicting the static viscoelastic behaviors of the samples, because the dynamic viscoelasticity of liquid food materials have been discussed mostly using these two-element models. Measurements using the NRCC method yielded mainly two types of force-time curves for the liquid samples. One type was a convex force-time curve, and the other was an almost linear curve. The analytical results showed that the former curve corresponds to the Maxwell-model materials, whereas the latter curve corresponds to the Voigt-model materials. The results indicate that the liquid materials with high dispersed-phase content (volumetric ratio φ> 0.75) showed Voigt-model-like behavior, while lower-concentration liquids showed Maxwell-model-like behavior.
