Effects of Cocrystallization between Different Amylopectin Fractions and Sodium Oxalate on Their Physicochemical Properties

Abstract

In order to prepare amylopectin with typical characteristics, amylopectin fractions isolated from mung bean, pea, cassava, sweet potato, potato, maize, and wheat starch were cocrystallized with sodium oxalate, and their physicochemical properties were investigated by optical microscopy, molecular weight and chain length distribution, X-ray diffraction, visible light absorption, and DSC. The results showed that all the cocrystals with a dendritic shape consisted of a barbell-shaped center and several large branches. After 72 h of eutectic process, the maximum visible light absorption wavelengths of all amylopectin turned to around 592 nm. In addition to pea and potato amylopectin, the eutectic process for 72 h increased the molecular weight of the other five amylopectin species, and the components of mung bean amylopectin were changed from two to one during the eutectic process. Cocrystallization narrowed the chain length distribution of all amylopectin chains, with the mung bean amylopectin side chains being the shortest. The X-ray diffraction results indicated that amylopectin may be complexed with sodium oxalate. All the cocrystals displayed two separate small endothermic peaks, with Tp around 97 °C and that above 170 °C related to the gelatinization of amylopectin segments within cocrystals and the dissociation of sodium oxalate/amylopectin complex, respectively. The formulation of cocrystals will be a promising strategy to tune the physicochemical properties of amylopectin.