pH-driven polyphenol-polysaccharide co-assembly for constructing curcumin-carrageenan complexes: Intestinal targeted, pH-responsive controlled release, and bioaccessibility enhancement in functional beverages.

In this study, a simple, green, and efficient pH-driven polyphenol- polysaccharide co-assembly strategy was adopted to prepare curcumin-carrageenan complexes for enhanced encapsulation, intestinal targeting delivery, controlled release, and bioaccessibility of curcumin in functional beverages. Results showed that stable complexes (355.7 nm, -39.5 mV) were formed at a curcumin to carrageenan mass ratio of 1:10, achieving efficient curcumin loading (encapsulation efficiency: 76.0 %, loading capacity: 6.9 %). Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), enhanced sampling molecular dynamics simulation (ESMDS), and scanning electron microscopy (SEM) confirmed that curcumin was mainly bound to carrageenan through hydrogen bonds and hydrophobic interactions to form a uniformly dispersed amorphous granular morphology with high tolerance to ion strength (0-500 mM) and pH (3-8). Carrageenan encapsulation significantly enhanced the DPPH and ABTS+ free radical scavenging activities of curcumin. The complexes aggregated during simulated gastric fluid digestion and degraded during simulated intestinal fluid digestion, thus inhibiting the release and decomposition of curcumin in the gastric fluid and significantly increasing curcumin bioaccessibility from 36.1 % to 52.2 % (p < 0.05). The release data showed that the complex enables the controlled release of curcumin during in vitro digestion, and its drug release characteristics conform to the first-order kinetic equation (Qinf of 64.498; k of 0.450). Current study will provide a theoretical basis for the green and efficient preparation of polysaccharide-based polyphenol delivery systems and their application in functional beverages.