Abstract: In order to improve the stability and sustained release property of black rice anthocyanin (BRA), chitosan was used to encapsulate BRA by ionic coacervation method with γ-polyglutamic acid (PGA) under pH-driven conditions in this study. Using combination of one-factor-at-a-time method and response surface methodology with particle size and encapsulation efficiency as response variables, the optimal preparation conditions were obtained as follows: chitosan concentration 0.8 mg/mL, PGA-to-chitosan ratio 7:20, BRA concentration 1.98 mg/mL, pH 5.0 and stirring time 30 min. The encapsulation efficiency and loading efficiency of the BRA nanoparticles prepared using the optimized conditions were 50.90% and 4.77%, respectively, with particle size of (352.95 ± 6.42) nm, PDI of 0.23 ± 0.02, and zeta potential of (29.56 ± 1.09) mV, suggesting small particle size and good dispersion stability. Observation by scanning electron microscope (SEM) demonstrated that the nanoparticles of BRA were spherical in shape. Compared with free BRA, the release rates of the BRA nanoparticles in simulated gastric and intestinal fluids were reduced by 52.65% and 36.69%, respectively, indicating that the prepared BRA nanoparticles have good sustained release property and thus have good application prospects.

Key words: black rice anthocyanin; response surface optimization; nanoparticle; sustained release property