Study on preparation and stability of anthocyanin microcapsules from purple rice straw

<bold>Objective</bold> The long-term and stable storage of anthocyanin microcapsules from purple rice straw by embedding into microcapsules is explored to realize the high-value utilization of agricultural waste. <bold>Method</bold> Using anthocyanin extract as the core material，and sodium alginate and chitosan as wall materials，the anthocyanin microcapsules from purple rice straw were prepared by the orifice method.It is made into a solid preparation by lyophilization.A single-factor experiment was conducted to investigate the effects of different factors on the encapsulation efficiency of purple rice straw anthocyanin microcapsules，and the preparation process was optimized using response surface experimental design.The properties and characteristics of the microcapsules prepared under optimal conditions were measured and characterized，followed by stability tests and in vitro digestion experiments. <bold>Result</bold> （1）Under the conditions of 25.5 g/L sodium alginate concentration，9.2 g/L chitosan concentration，10.5 g/L calcium chloride concentration，and core-to-shell material ratio of 1∶12，the encapsulation efficiency of anthocyanin microcapsules reached 72.073%.（2）The size of the microcapsules was determined，and both macroscopic and microscopic morphologies were observed，indicating uniform size and regular shape；the moisture content of the wet capsules was found to be 96.685%，while that of the freeze-dried microcapsules was 8.32%.（3）XRD characterization of the microcapsules and their wall materials further verified the encapsulation effect.（4）Stability tests under different light conditions and temperatures showed that the retention rate of anthocyanin in microencapsulated purple rice straw was higher than that of the unencapsulated anthocyanin extract.（5）After 360 min，the cumulative release rate of anthocyanin in simulated gastric fluid was 46.33%，and that of anthocyanin in simulated intestinal fluid was 77.25%. <bold>Conclusion</bold> The encapsulation efficiency of anthocyanin microcapsules prepared under optimal conditions can reach 72.073%.The freeze-dried microcapsule finished products have a good morphology and a low water content，indicating effective encapsulation.Microencapsulation of anthocyanins improves their stability under temperature and high-temperature conditions.Anthocyanin microcapsules show good sustained release properties in both simulated gastric and intestinal fluids，with significantly higher release in simulated intestinal fluid compared to simulated gastric fluid.