Multi-layer mucilage of Plantago ovata seeds: Rheological differences arise from variations in arabinoxylan side chains.

Mucilages are hydrocolloid solutions produced by plants for a variety of functions, including the creation of a water-holding barrier around seeds. Here we report our discovery of the formation of three distinct mucilage layers around Plantago ovata seeds upon their hydration. Each layer is dominated by different arabinoxylans (AXs). These AXs are unusual because they are highly branched and contain β-1,3-linked xylose in their side chains. We show that these AXs have similar monosaccharide and linkage composition, but vary in their polymer conformation. They also exhibit distinct rheological properties in aqueous solution, despite analytical techniques including NMR showing little difference between them. Using enzymatic hydrolysis and chaotropic solvents, we reveal that hydrogen bonding and side chain distribution are key factors underpinning the distinct rheological properties of these complex AXs.