Phycocyanin-loaded double emulsion gels stabilized by genipin-crosslinked carboxymethyl chitosan and whey protein isolate conjugates: Highlighting superior stability and sustained release

To improve storage stability and achieve sustained release of phycocyanin (PC), conjugates of carboxymethyl chitosan (CMCS) and whey protein isolate (WPI) crosslinked with genipin (GP) were developed. These conjugates were used to stabilize water-in-oil-in-water (W₁/O/W₂) double emulsion gels (DEGs). Conjugates with five different CMCS-to-WPI mass ratios (3:1, 5:3, 1:1, 3:5, and 1:3) were prepared. The encapsulation efficiency (EE), storage stability, rheological and textural properties, and release behavior of PC in the DEGs were systematically investigated. FTIR analysis confirmed the formation of covalent bonds between CMCS and WPI induced by GP crosslinking. Among all formulations, the DEGs stabilized by conjugates containing 1.5% CMCS and 2.5% WPI exhibited the most promising characteristics: the highest EE (99.89%), smallest droplet size (8.62 μm), and superior textural properties (hardness: 0.38 N; springiness: 0.91; cohesiveness: 0.50; chewiness: 12.20; gumminess: 12.98, gel strength: 110.99 g·mm). The in vitro digestion studies revealed minimal PC release in simulated gastric fluid, followed by sustained release in the intestinal phase. The release kinetics were best described by the Korsmeyer-Peppas model, indicating a Fickian diffusion mechanism (n < 0.45). This work highlights the potential of GP-crosslinked CMCS-WPI DEGs as an effective and robust platform for the targeted intestinal delivery of hydrophilic bioactive compounds like PC.