High-amylose starch nanocrystals produced via sulfuric acid hydrolysis and ultrasonication: Impact on resistant starch content and emulsification capacity

Abstract

Combined ultrasound–sulfuric acid hydrolysis is an efficient approach for preparing starch nanocrystals, but its application to high-amylose corn starch (HAS) remains underexplored, particularly in terms of its effects on emulsifying capacity and resistant starch (RS) content. In this study, HAS was treated with combined ultrasound–sulfuric acid hydrolysis for 1, 3, 5, and 7 days. The resulting nanocrystals (HNC) were characterized for particle size, zeta potential, crystalline structure, ATR-FTIR spectra, amylopectin chain-length distribution, RS content, and morphology. Their emulsion-stabilizing performance was evaluated under various environmental conditions, including pH, NaCl concentration, storage, and centrifugation. As the treatment time increased (from day 1 to day 5), particle size decreased while relative crystallinity (RC) increased. HNC-5d exhibited the smallest particle size (292.3 nm), highest RC (72.3 %), and maximum RS content (68.8 %). However, prolonged treatment (beyond 5 days) resulted in structural degradation, leading to increased particle size and reduced RC and RS content. Emulsions stabilized by HNC-5d showed superior emulsifying capacity and environmental stability. These findings elucidate how treatment duration affects HNC structure and support its potential as a low-sugar Pickering emulsifier. Future research may optimize processing and validate the delivery performance and digestive fate of HNC in complex food systems.