Gum arabic modulates mechanical properties and microstructural transition in whey protein isolate hydrogels

This study systematically investigated how whey protein isolate (WPI) to gum arabic (GA) mass ratios govern the structural transition from fine-stranded to particulate hydrogel networks and analyzed the resulting chemical, viscoelastic, and mechanical properties. WPI slab hydrogels with protein concentrations of 10-20% (w/v), and various WPI:GA mass ratios (20:1 to 2.5:1), were characterized via electron microscopy, Fourier-transform infrared spectroscopy, oscillatory rheology, and mechanical testing, including: frequency and strain sweeps, uniaxial compression, creep recovery, stress relaxation, and Burgers viscoelastic modeling. The WPI:GA mass ratio was found to alter the hydrogels' microstructures and scale mechanical properties over multiple orders of magnitude, enabling production of biomaterial-based gels with widely varied characteristics for engineering applications. The addition of GA to WPI gels up to an approximate 5:1 WPI:GA mass ratio yielded enhanced Young's elastic modulus (E) and dynamic moduli (G', G") while developing the gels' permanent crosslink network as quantified by relaxation modulus G(t), frequency dependence, and creep recovery behavior. The 5:1 WPI:GA ratio also represented an approximate phase transition point with gels above this ratio adopting fine-stranded microstructures and gels below adopting particulate microstructures. The fundamental structure-property relationships established here provide a foundation for development of WPI:GA hydrogels as a tunable platform.