Development of the pH responsive chitosan-alginate based microgel for encapsulation of Jughans regia L. polyphenols under simulated gastrointestinal digestion in vitro

The present research was designed to fabricate a novel pH-responsive microgel based on chitosan/sodium alginate (CS/ALG) to encapsulate the polyphenols from the shells of Juglans regia L. (JRP-Microgel), and investigate the physicochemical properties of JRP-Microgel as well as analyze the release characteristic and phenolic composition variation under simulated gastrointestinal digestion in vitro. The results showed that JRP-Microgel belonged to semi-crystalline substances, and presented regular spherical or subspherical shape with neat edge and uniform particle size. JRP-Microgel possessed better physicochemical stabilities compared with unencapsulated JRP. Furthermore, JRP-Microgel exhibited excellent sustained release characteristic under simulated gastrointestinal digestion. Nevertheless, during different digestive phase, the phenolic composition of microgel was significantly different from the one of untreated JRP, suggesting that JRP-Microgel could prevent the degradation of JRP induced by gastrointestinal digestion. In conclusion, above results provide the experimental basis for the application of microgel encapsulation to improve the bioavailability of phenolic compounds in human body.