Abstract: The present invention is a process for purifying polydextrose to remove manufacturing contaminants such as glucose, sorbitol, citric acid, oligomers, 1,6-anhydroglucose, 5-hydroxymethylfurfural and other low molecular weight constituents by reverse osmosis wherein an aqueous solution of polydextrose is filtered by pressing it tangentially over a porous membrane at high pressure. This invention process produces a purified polydextrose with the 1,6-anhydroglucose content therein reduced to less than about 0.2% (W/W) and a reduction in the 5-hydroxymethylfurfural content to below detectable levels or loss than about 0.01% (W/W), thereby virtually eliminating any bitter taste or musty off-flavor.