Ultrasound-Enzyme Synergistic and Octenyl Succinic Anhydride Dual-Modified Acorn Starch: A Green Carrier for Enhanced Stability and Sustained Release of Gentiopicroside

To solve the problem of limiting the application of the gentiopicroside, due to its poor chemical stability, this study proposes a green modification strategy based on renewable resources. Porous starch (PS) was prepared from acorn starch, a forest byproduct, by the ultrasonic-enzymatic synergistic technique and then modified by octenyl succinic anhydride (OSA) esterification to obtain a dual-modified carrier (PS-OSA) for the stabilization of gentiopicroside. Structural characterization showed that ultrasound-enzyme synergistic resulted in the formation of a rich porous structure, which enhanced the esterification efficiency of OSA (degree of substitution 0.0320 ± 0.0016), and gentiopicrosides could be embedded in its pores. After the optimization of response surface methodology (RSM) and particle swarm optimization-based support vector machine regression (PSO-SVR) models, the encapsulation efficiency under the optimal process reaches 77.89%, and the PSO-SVR model has a better prediction accuracy. The performance tests showed that the PS-OSA-encapsulated gentiopicroside microcapsules (PS-OSA/GR) had significantly improved thermal stability (93.15% retention at 65 °C for 24 h) and UV resistance (over 94% retention for 24 h of UV-A/B irradiation). The cumulative release rate was 58.69% at 360 min in simulated gastrointestinal fluid, which showed an excellent slow-release effect.