Effects of Degree of Polymerization on Size, Crystal Structure, and Digestibility of Debranched Starch Nanoparticles and Their Enhanced Antioxidant and Antibacterial Activities of Curcumin

The versatility of debranched starch nanoparticles (DBS-NPs) has attracted considerable attention from the food, agricultural, and cosmetic industries. The aim of this study was to investigate the effect of DBSs with low (DP < 10), moderate (10 > DP < 20), and high (20 > DP < 25) DPs (where DP represents the degree of polymerization), as well as reaction temperatures (25, 60, and 90 °C) on size, morphology, crystal structure, and digestibility of the refined DBS-NPs via nanoprecipitation. Spherical DBS-NPs with a controlled size of 40–200 nm were obtained; no nanoparticles were observed when the average DP was <10. The relative crystallinity increased from 11.1% to 71.6% as the increasing the average DP increased. When the microsized DBSs were converted to nanoscale DBSs, the rapidly digestible starch levels of the DBS-NPs decreased, and the DBS-NPs showed remarkable increase in the sum of slowly digestible starch and resistant starch contents, compared to the responding DBS. Furthermore, the maximum encapsulation efficiency of curcumin in DBS-NPs reached up to 92.49%. The antioxidant and antibacterial activities of curcumins in DBS-NPs were enhanced significantly, and their antioxidant stability was improved markedly when exposed to UV light or heat treatments.