Effect of in vitro digestion-fermentation of Ca(II)-alginate beads containing sugar and biopolymers over global antioxidant response and short chain fatty acids production

•Beads showed good antioxidant capacity during digestion assessed by several methods.•Up to ten-fold increase in the antioxidant values was observed after fermentation.•Guar and arabic gums show interesting behavior in the antioxidant response.•Production of SCFAs reveals the huge ability of beads to improve gut microbiota.•Beads partially dissolved their structure in intestinal fluid, where the absorption takes place. The aim of the present paper was to unravel the effect of a standardized in vitro European protocol of digestion-fermentation over Ca(II)-alginate beads synthesized with sugars and biopolymers. Special emphasis on the antioxidant capacity using methods that simulate physiological conditions, short-chain fatty acids (SCFAs) production, and a detailed study of the microstructure of the gel network by SAXS at several scales (1–100 nm) were considered. Beads released high antioxidant capacity during digestion assessed by several methods, comparable to some common foods; antioxidant capacity was improved with sucrose and arabic gum inclusion in the formulation. After fermentation by gut microbiota, a ten-fold increase in the antioxidant values and an important SCFAs production were obtained, revealing the enhanced ability to produce these functional biomolecules. The microstructural analysis of Ca(II)-alginate showed an advantageous behavior: they slightly changed in oral and gastric fluids and partially dissolved their structure in intestinal fluid, where absorption occurs.