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Description
Seaweed-derived polysaccharides such as agar, alginate, carrageenan, and cellulose are increasingly incorporated into food formulations due to their technological and nutritional properties. However, their impact on the gastrointestinal digestion of other food components, in particular proteins, remains poorly understood. In this work, we investigated how different seaweed polysaccharides affect the in vivo digestion of protein-rich diets and their influence on the structural organisation of the resulting ileal digesta under physiological conditions using a pig model.
Nutritionally balanced diets containing model food proteins like casein and whey protein isolate, combined with selected polysaccharides, were fed to pigs fitted with a distal ileal T-cannula. Digesta samples were collected from the terminal ileum and characterised in terms of compositional analysis and a multi-technique approach combining rheology, confocal microscopy, transmission electron microscopy, and small-angle X-ray scattering (SAXS), performed at the ALBA Synchrotron.
Protein digestion was extensive in all formulations, indicating that the inclusion of seaweed polysaccharides did not impair protein bioavailability. Nevertheless, marked differences were observed in the organisation of the undigested material. Confocal microscopy and SAXS revealed that each polysaccharide generated distinct structural environments within the digesta. Alginate promoted the formation of dense heterogeneous networks, whereas agar produced more homogeneous microstructures. Cellulose-containing formulations exhibited pronounced SAXS features associated with ordered nanoscale assemblies, which were consistent with bile salt nanomicelles. These structural differences were accompanied by variations in viscosity and colloidal organisation. The results demonstrate that dietary polysaccharides can substantially modify the multi-scale architecture of intestinal digesta without affecting overall protein digestion. SAXS proved particularly valuable for identifying nanoscale structural rearrangements that are not accessible through other techniques. Understanding how food components influence digesta structure may contribute to the rational design of foods with targeted digestive and nutritional functionalities