Exploring the mechanism of pullulan delay potato starch long-term retrogradation from the viewpoint of amylopectin chain motion.

Starch retrogradation is an inevitable process in the natural state caused by movement of starch chains. Therefore, the objective of this study was to explore the essence of starch long-term retrogradation from the viewpoint of amylopectin chain motion. The radius of gyration (R_g) and form factor (ρ) values of potato starch (PS) and PS with pullulan (PS-PUL) gradually increased during the retrogradation process. Furthermore, the conformation of molecular chains evolved from spherical to ellipsoidal to rod-like during starch retrogradation. Based on the analysis of condensed matter theory, these results illustrated that starch chains from gelatinization to retrogradation experienced shrinkage to extension. The values of R_g and ρ of PS-PUL were lower than PS, and the evolution of conformations showed that PUL delayed the long-term retrogradation of PS by decreasing the motion of amylopectin molecular chains to increase chain flexibility, and decrease the degree of entanglement and crosslinking. This study provides a novel method for characterizing starch retrogradation on the molecular level.