Preparation and physicochemical characterization of debranched rice starch nanoparticles from mono- and dual-modification by hydrothermal treatments

Starch nanoparticles (SNPs) are attracting attention due to their novel attributes beneficial to certain applications; their fabrication technique and physicochemical attributes have yet to be systematically investigated. In this study, starch nanoparticles were fabricated from the debranched rice starches of three rice lines employing the mono-modification by annealing treatments for one and five days and the dual-modification by the combined annealing and heat-moisture treatments, and their physicochemical properties were characterized. The highest percent recovery of crystalline SNPs was obtained by the dual-modification treatments (32.6-45.6%), followed by the five-day annealing treatment (23.8-28.7%), and then the one-day annealing treatment (11.7-15.8%). The modified starches showed significant increases in oil absorption capacity, water holding capacity, and solubility and decreases in swelling power and volume fraction compared to their native counterparts. The crystal types were changed from A-type to B-type polymorphs by mono-modification treatment and to CA-type polymorphs by the dual-modification treatment with significant increases in relative crystallinity. The dual-modification treatment resulted in the highest increases in 1047/1022 cm-1, 995/1022 cm-1, and 1047/1035 cm-1 band ratios and the highest melting temperatures and enthalpies. The resistant starch contents of the modified starches were markedly increased and strongly related to the percent recovery and the short-and long-range ordered structures. The results suggest that the dual-modified starches comprised the rigid and densely packing of nanoaggregates with superior oil/water absorption performance and water dispersibility, and high enzymatic resistance, which could be the contributing factors for their utilizations as novel ingredients in food-related applications.