Rheology of fluid foods containing millimeter-sized ingredients examined by velocity-profiling-assisted rheometry and prediction of spreading and descending behaviors

As representatives of fluid foods containing millimeter-sized ingredients, three kinds of rice porridge are examined by velocity-profiling-assisted rheometry (VPAR). The obtained flow curves of the plain, egg, and bean porridge are well characterized by the power-law model, where the plain porridge has the highest consistency, the bean porridge is the second, and the egg porridge has the lowest viscosity. These are also time dependent properties; the consistency and the degree of shear-thinning decrease as the measurement repetition proceeds. With these rheology data, spreading and descending behaviors, which are fundamental and important flows in the eating and swallowing process, are discussed. Spreading behavior in the conventional line spread test and descending behavior in a simplified artificial throat model are predicted based on the rheological data identified by VPAR and simple physical models. The spreading behavior is validly described by the consistency, and the descending velocity is evaluated to have high correlation with the representative shear rate predicted. Through the rheological measurement and its application to rationalize the flow behaviors, VPAR is expected to be a practical tool in both rheology and fluid mechanics of complex fluid foods.