Precipitation from alcohol used against fractionation of polysaccharides was applied as an energy-efficient chemical modification with only a co-precipitation of polysaccharide and the modifying agent in polar organic solvents, and drying. Addition of ethanol caused a conformational change of polysaccharides with increasing intramolecular hydrogen bonding and a dense structure in close proximity to atoms, especially, in the presence of modifying agents. Extent of modification depended on the structure of polysaccharides and pH in polar organic solvents. The co-precipitates in polar organic solvents seem to act as a precursor while still maintaining the integrity of the modified polysaccharides. Eventually, a small amount of polar organic solvents (1.5 times volume to the weight of the mixtures) to disperse the reaction mixtures was enough to complete modification.