Arabinan

Arabinan is a plant polysaccharide composed predominantly of L-arabinofuranose units. The polymer typically features a backbone of mainly α-1,5-linked arabinose residues, with shorter side chains of arabinose attached by α-1,2- or α-1,3-linkages. In plant cell walls, arabinan commonly occurs as part of rhamnogalacturonan I (RG-I) in pectin, where arabinan side chains are covalently attached to the RG-I backbone at rhamnose residues. Arabinan is also found in various plant gums and pectic extracts, such as gum arabic and citrus pectin, contributing to their structural and rheological properties.

In functional terms, arabinan contributes to the flexibility and solubility of pectin-rich materials and influences gelation and thickening behavior in foods and other formulations. The exact properties of arabinan-containing polymers depend on the length of the backbone, the extent of branching, and the pattern of substitutions.

Analytically, arabinan is typically quantified after hydrolytic cleavage to release arabinose and, in some cases, subjected to more detailed structural analysis by methods such as NMR and methylation analysis. Enzymes that degrade arabinan, known as arabinanases, are of interest in food processing and biomass conversion.

Biologically, arabinan is a dietary fiber component that resists digestion in the human small intestine and is fermented by gut microbiota, producing short-chain fatty acids and other metabolites. This fermentation can contribute to gut health and is a subject of ongoing nutritional research.