Long-term retrogradation properties of rice starch modified with transglucosidase

The retrogradation properties of rice starch (RS) treated with transglucosidase (TG) were investigated. The degree of branching (DB) increased from 12.26 to 15.16% with increasing TG treatment time except for 20 h. The relative crystalline of the retrograded TG-treated starches decreased from 26.44 to 21.57% with increasing DB. While the crystalline peak intensity became narrower and sharpener due to the formation of a much more uniform crystal structure, hence resulting in a lower mobility of water. Also, the spin-spin relaxation time (T2) decreased with increasing DB. The T22 and T23 significantly decreased by 80.47 and 64.46%, respectively. The Avrami kinetics demonstrated that the retrogradation rate of rice starch was retarded due to the decrease of rate constant k after TG treatment. The study may provide a promising theoretical basis on retarding retrogradation of rice starch to improve the qualities and extend shelf life of the rice staple foods.