The roles of amylose and amylopectin in the gelation and retrogradation of starch

The retrogradation of starch gels has been studied by using X-ray diffraction, differential scanning calorimetry, and measurements of the shear modulus. Starch gels were considered as composites containing gelatinised granules embedded in an amylose matrix. The short-term development of gel structure and crystallinity in starch gels was found to be dominated by irreversible (T <100°) gelation and crystallisation within the amylose matrix. Long-term increases in the modulus of starch gels were linked to a reversible crystallisation, involving amylopectin, within the granules on storage. It was considered that the crystallisation resulted in an increase in the rigidity of the granules and thus enhanced their reinforcement of the amylose matrix.