α-amylase-assisted spherical starch nanoparticles production from waxy rice starch by pullulanase debranching and nanoprecipitation: Structural and functional insights

In this study, α-amylase was used to assist starch nanoparticles (SNP) production through debranching and nanoprecipitation. The molecular structure, aggregation behavior, morphological properties, and digestibility of SNP were investigated. α-amylase hydrolysis pretreatment for 4 h increased the short-chain ratio of SNP, with a peak at DP = 13. This facilitated the formation of smaller and more uniform SNP, particularly at higher antisolvent concentrations. With α-amylase pretreatment, the small molecules reduced steric hindrance and interparticle interaction, resulting in a compact structure and well-defined boundaries during nanoprecipitation as indicated by cryo-EM. The crystalline pattern was mostly influenced by the solvent-to-antisolvent ratio. Prolonging α-amylase hydrolysis time led to loss of long-range crystalline order in SNP, while promoting the formation of submicron crystallites. Additionally, pretreatment increased slowly digestible starch and resistant starch ratios, leading to a lower glycemic response, thereby improving their functional performance. These findings offer valuable insights for optimizing the nanoprecipitation to produce SNP with controlled size and morphology, which enhances their potential as carriers in delivery systems.