Rheological properties of inulin–waxy maize starch systems

Abstract

The rheological properties of mixed systems of inulin and waxy maize starch (WMS) were studied, as a model of carbohydrate–carbohydrate interactions in foods. Steady shear and oscillatory rheological properties were analyzed using a strain-controlled rheometer. Steady shear data were satisfactorily fitted to the Carreau model. The data were also fitted to the Herschel–Bulkley model. Concentrated inulin gels presented static and dynamic yield stresses. Phase inversion from a WMS-continuous system to an inulin-continuous system, manifested as a sudden change in rheological properties, was observed in samples with a total polymer concentration ≥30% (w/w, w.b.). In order to validate the oscillatory rheological data, some samples were subjected to stress relaxation experiments and both types of data were compared, showing a satisfactory agreement. The Cox–Merz rule, which relates steady shear and dynamic material functions, was not followed by most of the samples. An extended Cox–Merz rule was applied to the analysis of concentrated inulin gels.