Adsorption of polyphenolic compounds by sodium alginate-modified starch nanoparticles in a multiphase system: Kinetic, thermodynamic and release characteristics studies

Starch nanoparticles (SNPs) have been recognized as potentially efficient adsorbents for polyphenols. However, their actual adsorption in complex systems such as fruit pomace extract is significantly lower than theoretical predictions and their adsorption capacity is inferior to traditional materials such as macroporous adsorbent resins, which limits their industrial application. Aiming to enhance the adsorption of apple pomace polyphenols, this study used sodium alginate (SA) modifies SNPs to create a cornstarch-based composite system (SA-SNPs). The optimal modified addition of sodium alginate was 0.3 g (g starch) −1 , under this condition, the nanoparticles obtained exhibited the smallest particle size (154.60 nm) and the best adsorption performance (33.97 mg g −1 in 90 min). The SA-SNPs reached the adsorption equilibrium at 180 min, which significantly enhanced the equilibrium adsorption amount of the polyphenols (from 2.68 to 37.02 mg g −1 ). The adsorption process was found to follow the pseudo-second- order kinetic model and the Langmuir isotherm model, which included membrane diffusion, intra-particle diffusion, and equilibrium phases. The adsorption amount initially increased and then continued to decrease with the increase in temperature, and the whole process was exothermic and spontaneous (ΔH° = −52.394 kJ mol −1 , ΔG° < 0 kJ mol −1 ). Additionally, SA-SNPs loaded with polyphenols demonstrated better protection of polyphenol DPPH radical-scavenging activity during storage, enhanced stability, and optimal colon-targeted sustained-release properties in complex physiological environments. This work presents a new approach to improving the adsorption capacity of SNPs and developing high-performance natural edible separation materials.