Fe3+-EGCG metal-phenolic networks modified soy protein isolate nanoparticles for colloidally stable Pickering emulsions with colon-targeted curcumin release

Abstract

Soy protein isolate (SPI) has shown promise as an emulsifier and carrier for bioactive compounds in food applications, but its instability at the oil-water interface under environmental changes remains a significant limitation. Current strategies to enhance SPI stability including complexation with polysaccharides or polyphenols and controlled hydrolysis have improved functional performance, but emerging approaches such as metal–phenolic networks (MPNs) offer promising new avenues for further increasing emulsion stability. This study investigated the self-assembly mechanism of Fe 3+ -EGCG networks on SPI nanoparticles and evaluated their stability under varying temperatures and ionic strengths. Among the tested formulations, SPI nanoparticles modified with the highest Fe 3+ -EGCG ratio (denoted as SPI-(E-Fe)4) showed bis- and tris-type coordination confirmed by FTIR and LMCT bands. Particle size ranged 268–472 nm, with stable zeta potential above 30 mV. SPI-(E-Fe)4 maintained stability under heat and salt stress, formed cubic structures, and achieved higher curcumin encapsulation (82.71 %) than SPI-NPs (79.17 %). SPI-(E-Fe)4 emulsions exhibited improved curcumin retention under UV and storage, and superior stability during digestion, with controlled curcumin release. These results highlight the Fe 3+ -EGCG network's potential to advance protein-based nanoparticles and active compound delivery systems. • Fe 3+ -EGCG networks enhanced the stability of soy protein isolate nanoparticles. • SPI-(E-Fe)4, SPI nanoparticles with the highest Fe 3+ -EGCG ratio, maintained stability under heat and salt stress. • Curcumin retention was significantly improved in SPI-(E-Fe)4 emulsions. • SPI-(E-Fe)4 emulsions showed controlled curcumin release during digestion.

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