Effects of molecular weight of chitosan on its binding ability with OSA starch and oil-water interface behavior of complex-stabilized emulsion

This work examined the effects of molecular weight (2-15 kDa) and concentration (10-30 mg/mL) of chitosan (CTS) on the binding capacity and interface behavior between octenyl succinic acid sodium starch (OSS) and CTS, as well as their effects on the storage stability of emulsions. The results of the isothermal calorimetry titration demonstrated that OSS and CTS were complexed by electrostatic interaction and spontaneous hydrogen bonding driven by enthalpy (ΔH from -3931 to -7983 cal/mol, ΔS from -38.5 to -49.2 cal/mol/deg., ΔG from -6436.6 to -7542.0 cal/mol), and the affinity and binding capacity (N = 2.83-22.90 sites) were reinforced with CTS molecular weight. The interfacial adsorption kinetics revealed that the OSS/CTS complexes with high-molecular-weight CTS exhibited a markedly accelerated rate of interfacial diffusion and recombination, and rapidly reduced interfacial tension. CTS incorporation enhanced mass (1980.32-3522.56 ng/cm²), thickness (35.12-51.29 nm), viscosity (52.81-67.06 kPa), and elasticity (1.70-3.49 kPa) of interfacial film through the dissipative quartz crystal microbalance. OSS/CTS complexes displayed superior emulsification properties and adjustable interfacial viscoelastic ratio in response to frequency interference. Emulsions stabilized by the OSS/CTS complexes with high molecular weight and concentration of CTS exhibited more uniform spherical structures and superior storage stability. This work will facilitate the broader utilization of OSS and CTS in the emulsion delivery system.