Structure and physicochemical properties of arabinan-rich acidic polysaccharide from the by-product of peanut oil processing

Abstract In this work, the fine structure and physicochemical properties of acidic peanut polysaccharide (APP) from sediment of aqueous extraction process were investigated. Methylation results revealed that arabinose, galactose, rhamnose, xylose and 1,4-linked galacturonic acid together constituted the APP, of which arabinose occupied 58.5%. The degree of branching of APP was 63.61%. Combining with 1D/2D NMR analysis indicated a large amount of highly branched 1,5-α-arabinan were formed by multi-substituted α-Araf residues and a few β-Galp residues were connected each other. The multi-substituted α-Rhap residues and α-1,4-GalpA were linked through 1,2 or 1,4-O-glycosidic bonds, maintaining the core structure of APP. Moreover, partial Araf residues were linked to the Rhap residues through 1,3-O-glycosidic bond. This indicated the presence of RG-I region in APP. Meanwhile, the ratio of RG-I approximately was 83.9%. The proportion of (Ara+Gal)/Rha was 8.5, suggesting the abundant neutral side chains to the RG-I. HG region occupied 4.4% of APP. On the other hand, APP exhibited strong charge and high transparency at pH3.5-11.0. Meanwhile, the turbidity of 15.0% APP only was 0.18. Divalent cations (Ca2+, Fe2+ and Zn2+) were strongly bound to APP. Moreover, the APP-Fe2+ complex formed strong gel. This information would be helpful for exploring the application of APP.