Metal-phenolic network coordination-mediated assembly of whey protein isolate gels: Structural evolution, functional...

Traditional whey protein isolate (WPI) gels lack stability and controlled release during digestion. Compared to single-crosslinked carrier systems, modifying WPI with dynamic metal-phenolic networks (MPNs) offers a superior strategy with highly tunable cross-linking to overcome these limitations. This study aimed to develop MPN-WPI gels for targeted glycyrrhizic acid delivery. We tested nine clear treatments. These combined three phenolic acids (chlorogenic acid (CA), gallic acid (GA), rosmarinic acid (RA)) with three metal ions (Cu²⁺, Fe³⁺, Zn²⁺). Spectroscopy results confirmed the presence of covalent bond, hydrogen, and coordination bonds. The metal coordination bond formed between RA and Fe³⁺ was the strongest. Consequently, WRA@Fe gels achieved the highest β-sheet content (48.52%). MPNs significantly improved overall gel functionality. Specifically, WRA@Fe performed best. It got the excellent self-supporting properties macroscopically and highly uniform honeycomb-like porous network with tiny pores. During simulated digestion, different MPN combinations controlled the release kinetics. CA caused rapid gastric release. This peaked at 69.2% in WCA@Zn gels. Conversely, RA ensured a steady, sustained release throughout digestion. In conclusion, varying metals and phenolic acids precisely regulates gel functions. This study provides important insights into advancing the WPI carrier-bound phenolic acid-metal coordination strategy for functional foods and oral drug delivery.