Rheo-NMR: Applications to Food

Abstract

In food process engineering, the handling, pumping, extrusion, or mixing of highly concentrated disperse systems is of importance for initial, intermediate, or final products. Examples are suspensions (beer mashes, chocolate, dough), foams (protein-, carbohydrate-based), emulsions, porous solids (baked products), and dry/wet bulk solids (malt, sugar). Although plenty of information concerning the rheology of multiphase system is available, the modeling of the flow behavior, structure of the produced system, and its stability cannot be considered as totally completed. In spite of its great importance, the determination of viscosities of disperse systems is difficult in principle [1,2]. Defined velocity profiles in rheometers (so-called viscometric flows), the homogeneity of the sample during the experiment, and applicability of continuous mechanics are usually prerequisites for rheometric studies. In disperse multiphase systems, demixing (phase separation: sedimentation, creaming, wall layers), scale effects [3], preparation, time effects (crushing, de-/agglomeration), tearing apart (fat, ointments), and wall slip cause problems when studying the flow behavior and determining flow functions of disperse systems with conventional rheometric methods.