Preparation, characterization, and stability of mulberry anthocyanins in silk fibroin/β-cyclodextrin composite...

This study investigated the encapsulation of mulberry anthocyanins using silk fibroin (SF), β-cyclodextrin (β-CD), and their composite (SF/β-CD) as wall materials. The encapsulation efficiency (EE) was optimized by adjusting the core-to-wall ratio and composite wall composition. Results showed that the highest EE of 85.39% was achieved at a core-to-wall ratio of 1:10 with an SF/β-CD ratio of 1:1. Thermogravimetric analysis demonstrated that the initial decomposition temperature increased from 83.47 °C for anthocyanins to 168.80 °C for microcapsules, indicating significantly improved thermal stability. Scanning Electron Microscope (SEM) observations revealed spherical and smooth microcapsules with an average diameter of 1-2 μm. X-Ray Diffraction (XRD) patterns confirmed higher crystallinity in the microcapsules compared to anthocyanins. In antioxidant assays, the SF/β-CD microcapsules exhibited stronger 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities than anthocyanins, maintaining stable antioxidant performance over time. In vitro digestion studies showed that microencapsulation enhanced anthocyanin retention by 18.31% as compared to unencapsulated anthocyanin after 3 h of simulated intestinal digestion. Additionally, the hygroscopicity of microcapsules decreased to 48.17% after 25 days under 50% relative humidity, compared with 65.13% for anthocyanins. Color stability analysis under light exposure demonstrated that the ΔE values was reduced from 4.68 (unencapsulated anthocyanin) to 4.18 (microcapsules) after 11 days. These findings confirm that SF/β-CD composite microcapsules effectively enhance the stability, antioxidant activity, and controlled release of anthocyanins, indicating potential for functional food applications.