Some dietary fibres, especially soluble, due to their ability to modify the physical properties of digestive content, are associated with positive physiological effects. In this study, the effect of digestion on apparent viscosity and fragmentation/aggregation degree of different soluble fibres (guar gum, xanthan gum, pectin, and chia seed mucilage) were evaluated during in vitro digestion. All fibres showed pseudoplastic behaviour independent of the concentration and digestion stage, but xanthan gum and mucilage retained more viscosity compared with the other fibres. Particle size during digestion showed that pectin and guar gum had different degree of fragmentation
at the intestinal level, while xanthan gum exhibited aggregation at the gastric stage and the chia mucilage remained unchanged during the digestion. The ability of xanthan gum and mucilage to conserve their structure and viscosity during digestion could help to modulate the digestive process, delay gastric emptying and enhance the functionality of foods.