Functional properties and Pickering emulsion stability of whey protein isolate-inulin complexes enhanced by covalent...

Ultrasound-assisted covalent modification offers a promising approach for fabricating protein-polysaccharide-polyphenol ternary complexes as advanced Pickering emulsion stabilizers, yet facile preparation strategies remain underexplored. This study aimed to develop an ultrasound-assisted covalent modification strategy for preparing whey protein isolate-inulin-proanthocyanidin (WPI-I-PC) ternary complexes and evaluate their functional performance, particularly as Pickering emulsion stabilizers.

The WPI-I-PC complexes were prepared by pH adjustment and wet-heating method with or without ultrasonic assistance. The incorporation of PC markedly decreased the particle size and surface hydrophobicity while altering the secondary structure of WPI. Compared with WPI-PC binary complexes (covalent or non-covalent) and WPI-I-PC ternary non-covalent complexes, the WPI-I-PC covalent complexes prepared with ultrasound-assisted wet-heating method at pH 10 exhibited superior thermal stability, emulsifying activity, and antioxidant capacity. Notably, ultrasound-assisted preparation for 72 min (WPI-I-PC (c)) achieved comparable functionality to the 4 h wet-heating method (WPI-I-PC (4 h)), with a smaller particle size (384.50 versus 476.03 nm). In Pickering emulsions, the WPI-I-PC covalent complexes markedly improved emulsion performance, as reflected by a reduction in flocculation index (from 32.00% for WPI to 7.92% for WPI-I-PC (4 h) and 8.24% for WPI-I-PC (c)) and an increase in interfacial protein adsorption content (from 76.80% to 84.92% and 84.37%, respectively). Furthermore, WPI-I-PC (c) demonstrated outstanding stability and enhanced antioxidant activities.

Ultrasound-assisted covalent modification enabled rapid fabrication of WPI-I-PC ternary complexes with enhanced structural and functional properties. The resulting Pickering emulsions demonstrated outstanding stability and antioxidant activity, offering an efficient strategy for developing novel food-grade emulsion stabilizers with potential applications in functional food delivery systems. © 2026 Society of Chemical Industry.