Branched arabinan obtained from sugar beet pulp by quaternization under acidic conditions

Sugar beet pulp was extracted and chemically modified under acidic conditions using glycidyltrimethylammonium chloride in the presence of trifluoroacetic acid (TFA), HCl or H3PO4. The goal was to find out how the used acid and quaternization could affect the yield of soluble polysaccharide, its molar mass, monosaccharide composition, and structure. The use of HCl and H3PO4 gave smaller yields of eluents when quaternized than in the presence of TFA at ambient pressure (10% of fraction over 10 kDa and 7% of a 1–10 kDa fraction). The monosaccharide composition analysis confirmed that the use of TFA for quaternization under vacuum resulted in fraction with the higher arabinose content (86%) than the use of HCl or H3PO4. The molar masses were similar as on analogical extracts obtained under alkaline conditions. The NMR data indicated that the arabinan structure is modified with the quaternary group at terminal C-5 of arabinofuranose unit.