The gelation and crystallisation of amylopectin

A range of physical and chemical techniques, including viscometry, rheological measurements, dilatometry, turbidity measurements, X-ray diffraction, and differential scanning calorimetry, has been used to study the gelation of amylopectin. Gels form on cooling concentrated aqueous solutions to 1°. The development of gel stiffness is closely related to the association of amylopectin chains, as monitored by dilatometry and differential scanning calorimetry. X-Ray diffraction studies suggest that intermolecular association involves a crystallisation process. The association of amylopectin chains in the gel is substantial and is thermo-reversible at temperatures below 100°. Heterogenous acid hydrolysis of the gel followed by examination of the residue by gel-permeation chromatography showed that the associated regions contained branched fragments, the individual chains of which had a d.p. of 15. The combined data suggest that the amylopectin molecules associate by crystallisation of the branches with d.p. 15 to form a network.