In vitro digestion of beta-glucan rich cereal products results in extracts with physicochemical and rheological behavior like pure beta-glucan solutions – A basis for increased understanding of in vivo effects

Sammendrag

Cereal beta-glucans may reduce fasting LDL-cholesterol and post-prandial blood glucose rise in humans. Several studies have shown that physicochemical properties of beta-glucan such as molecular weight (M) and solubility/extractability as well as the viscosity of food products after in vitro digestion are important for this physiological effect. In this study, we directly compare beta-glucan physicochemical properties and flow behavior of different cereal products after analytical (thermostable alpha-amylase) and physiological (in vitro digestion) extractions. The beta-glucan weight average molecular weights (Mw) were similar for both types of extractions, while differences in beta-glucan solubility between the food products were only evident after in vitro digestion. The extracts after in vitro digestion behaved essentially as pure beta-glucan solutions. Viscosity dropped to 0.8–1.2 mPa after incubation with a beta-glucanase for all extracts, but was not influenced by xylanase addition. The relationship of beta-glucan Mw (or intrinsic viscosity calculated from Mw), concentration and zero shear viscosity measured in the extracts closely resembled the general relationship reported for “random coil” polysaccharides with two distinct regions, below and above the occurrence of coil overlap. A standardized presentation of previously published in vivo data on blood glucose response showed a distinct grouping of samples with significant effect in the range of coil overlap. This points towards an important role of coil overlap for the reduction of post-prandial glycemic response by beta-glucan rich foods and demonstrates the potential of such a general comparison of different studies to increase the understanding of beta-glucan rich food products in vivo effects.