Encapsulation of astaxanthin by citric acid corn starch ester nanoparticle-based Pickering emulsion: Effect of amylose content

BACKGROUND: The effects of amylose content on citric acid starch ester nanoparticles through nanoprecipitation as Pickering emulsion stabilizers remain unknown. In this study, three types of corn starch with different amylose content, namely waxy corn starch (WCS), normal corn starch (NCS), and high-amylose corn starch (HACS), were used to prepare starch ester nanoparticles through nanoprecipitation. This research systematically studied corn starch ester nanoparticles with regards to the structural and interfacial properties at the oil–water interface and application to the delivery of astaxanthin in vitro. RESULTS: Corn starch ester nanoparticles exhibited the V-type crystalline pattern compared to the native starches showing either A-type (NCS and WCS) or B-type (HACS) patterns. Corn starch ester nanoparticles exhibited enhanced contact angle compared to those of native starches, with the order of waxy corn starch ester nanoparticle (WCSENP) > high amylose corn starch ester nanoparticle (HACSENP) > normal corn starch ester nanoparticle (NCSENP) (P ≤ 0.05). Starch ester nanoparticle-based Pickering emulsion (PE) showed increased storage stability at 4 and 25 °C, in contrast to those stabilized by native starches. Starch ester nanoparticle-based PE exhibited higher retention rate and bioaccessibility of astaxanthin (AST) than those of soybean oil (P ≤ 0.05). The AST retention curve of PE was fitted to the first-order kinetic model. The AST retention rate of WCSENP-PE remained above 70% after 8 days of storage at 25 °C, followed by HACSENP-PE and NCSENP-PE. CONCLUSION: This study provided a new strategy of producing PE stabilizers with improved properties, stability, and bioacessibility of bioactive compound in vitro. © 2026 Society of Chemical Industry.