Alginate-millet starch composite matrices as novel carriers for controlled delivery of grape seed polyphenols: Preparation, characterization, and in vitro release behaviour

Grape seed polyphenols (GSP) were encapsulated in alginate-modified millet starch composite matrix using internal gelation. Millet starch was modified using ultrasound (US) for 10, 20, 30, and 40 min. The application of US reduced the long-range order and increased the short-range order of starch, consequently increasing its solubility. FESEM analysis revealed that US-treatment induced fissures and grooves on the surface of starch granules and disintegrated the starch particles. Particle size distribution analysis confirmed a significant reduction in mean particle size. US-treatment facilitated enhanced alginate-starch interactions owing to an increased surface area and improved hydrogen bonding, as corroborated by FTIR, XRD, and DSC results. The composite microencapsulates prepared from 40 min US-treated starch demonstrated the highest encapsulation efficiency (89.20 ± 1.10 %), heat and UV-light stability, and delayed GSP release in simulated gastrointestinal fluids. The best fit for the release behaviour of GSP from the composite microencapsulates was observed with Peppas-Sahlin model.