STRUCTURE OF A GALACTOARABINAN-RICH PECTIC POLYSACCHARIDE OF NATIVE AND FERMENTED BLACKGRAM (PHASEOLUS-MUNGO)

Two homogeneous galactoarabinans containing similar to 15% D-galacturo nic acid were isolated and characterized from native and fermented bla ckgram. Linkage analysis indicated highly branched structures consisti ng of a (1 --> 5)-linked L-arabinan backbone additionally being substi tuted with L-arabinofuranose, D-galactopyranose, D-galactopyranosyluro nic acid and L-rhamnopyranose residues; a structure reminiscent of pec tic polysaccharides. Analysis of carboxyl-reduced polysaccharides show ed that the galacturonic acid residues are all essentially (1 --> 4)-l inked. The fermented polysaccharide had a relatively higher degree of branching which was manifested in its overall higher viscosity and as a result better product making qualities. The uronic acid carboxyls we re at least partly involved in maintaining the solution viscosity and functional property attributes, because the carboxyl-reduced polysacch aride was devoid of both these characteristics.