Impact of dual-enzyme treatment on the octenylsuccinic anhydride esterification of soluble starch nanoparticle

• Soluble starch nanoparticle was treated by enzymatic degradation and esterification.
• Dual-enzyme pretreatment increased the reaction efficiency of OSA modification.
• Position of ester groups in OSA modified starch nanoparticle was elucidated.
• Tailor-made OS-starch nanoparticle can improve the emulsion stability.

The hypothesis of improving the esterification of sugary maize soluble starch through dual-enzyme pretreatment was investigated. Native starch nanoparticle (NSP) was enzymatically pretreated using β-amylase and transglucosidase (ESP) and then esterified with octenylsuccinic anhydride (OSA). The degree of substitution (DS), reaction efficiency (RE), molecular weight (Mw), molecular density (ρ) and in vitro digestibility were determined. Fourier transform infrared spectroscopy and confocal laser scanning microscopy were used to analyze starch particle and its OS derivatives. The emulsification properties of OS-NSP and OS-ESP were also compared. The results showed that dual-enzyme modification increased the DS and RE of OSA modified starch particle compared with the control. Enzymatic modification had a thinning effect at the surface of starch particle, resulting in lower Mw. The extent of reduction in ρ of OS-ESP was greater than that of OS-NSP. At equivalent DS, OSA modification of EPS was more effective than that of NPS in reducing digestibility. Also, there was brighter fluorescence spheres of OS-ESP in comparison to OS-NSP at equivalent DS, suggesting more OS groups were substituted on the chains near the branch points at less density areas. OS-ESP with higher DS (0.0197) had lower zeta-potential and average particle size for superior emulsion stabilization properties with high stability. The results revealed the OS-starch prepared under dual-enzyme pretreatment was a Pickering particle stabilizer for potential application in encapsulation and delivery of bioactive components.