Regulated release of anthocyanins via gelatin/pectin composite gels in simulated digestion

The stable delivery of anthocyanins (ANCs) requires overcoming two core challenges: maintaining stability in gastric fluid and ensuring controlled release in intestinal fluid to improve their bioavailability. In this proof-of-concept study, we leveraged the abundant pH-responsive -COOH groups in pectin molecules to develop gelatin/pectin composite hydrogels capable of effectively encapsulating and releasing mulberry-derived anthocyanins. In the intestinal environment, carboxyl groups (-COOH) ionization leads to marked electrostatic repulsion among carboxylate ions (-COO - ). This intermolecular repulsion may disrupt the intermolecular forces that stabilize the hydrogel, ultimately causing structural destabilization. This process could promote the release of ANC molecules into the intestinal fluid, thereby facilitating their absorption by the human body. Specifically, we investigated the rheological properties, gel hardness, and microstructure of the gelatin/pectin composite hydrogels, confirming their structural suitability for efficient ANCs encapsulation. The thermogravimetric analysis further demonstrated their ability to protect anthocyanins against thermal stress. Subsequently, we systematically examined the effects of solid content, pectin-to-gelatin ratios, and pectin types on the hydrogels' encapsulation efficiency and gastrointestinal-responsive release behavior. This analysis identified an optimized composite hydrogel with high encapsulation efficiency (96.51 %), minimal release in gastric fluid (10.70 %), and substantial release in intestinal fluid (87.87 %). These findings indicate that pectin-based composite hydrogels may serve as effective carriers for the controlled delivery of anthocyanins, enhancing their bioavailability. Moreover, this study may provide a valuable framework for the design of delivery systems tailored for other food-derived bioactive compounds . Schematic presentation of this study that demonstrates the regulated release of anthocyanins using gelatin/pectin composite gels in simulated digestion. (SGF: simulated gastric fluid; SIF: simulated intestinal fluid). The highlights of our study can be summarized as follows. • Regulated and safe release of anthocyanin in simulated intestinal fluid • Stable encapsulation of anthocyanins within the network of gels • Diverse types of gelatin/pectin composite gels for tailored applications