Glycerol prevents the intermolecular association of linear dextrins after a gradient ethanol precipitation

The conventional gradient ethanol precipitation method often induces double-helical structures in linear dextrins, limiting their encapsulation potential. This study introduced glycerol to promote a V-type single-helical conformation after the gradient ethanol precipitation step, effectively suppressing double-helix formation. X-ray diffraction showed that ethanol-precipitated dextrins formed B-type crystals with crystallinity ranging from 14.21% to 36.66%. Upon glycerol treatment, B-type crystals were nearly absent while V-type crystals appeared (crystallinity 21.12-36.97%), confirming that glycerol inhibited the formation of B-type crystals composed of double-helix structures by promoting the formation of V-type crystals. Fourier transform infrared spectroscopy showed that glycerol treatment resulted in the characteristic peak of OH groups shifted to higher wavenumbers. Similarly, full width at half maximum at 480 cm^-1 in Raman spectroscopy increased from 32.49-34.98 to 35.13-37.76. These results indicated that glycerol impeded the association of linear dextrins by inhibiting hydrogen bond formation. This structural difference led to linear dextrins prepared by the glycerol-assisted method exhibiting about 15-fold higher iodine-binding capacity. Moreover, glycerol-treated dextrins effectively encapsulated lauric acid at low temperatures without additional unwinding steps. These findings demonstrated that glycerol effectively restricted the formation of double-helix structures, providing a feasible route to prepare linear dextrins ready for active substance loading.