Mesoscale fractal whey protein particles derived from microscale linear-shaped protein assemblies (Part 2): Foaming properties and heat stability.

This study investigates the functionality of mesoscale whey protein particles (WPP) derived from fiber- and ribbon-shaped whey protein assemblies produced via a liquid antisolvent precipitation-based method. The air-water (A-W) interfacial characteristics, foaming properties, and heat stability of WPP were evaluated and compared with the original whey protein source, whey protein isolate (WPI). Adsorption dynamics and dilatational rheology at the A-W interface were characterized using pendant drop and oscillating drop methods, respectively. Foamability and foam stability were assessed using a dynamic foam analyzer, and heat stability was evaluated by examining changes in particle size distribution (PSD) profiles and turbidity before and after heat treatment at 95°C for 5 min. Whey protein particles achieved a quasi-equilibrium surface pressure comparable to WPI after 3 h of adsorption but showed lower dilatational elastic moduli during dilatational deformation. Although WPI exhibited faster surface adsorption, no significant difference was observed in the rate constant of penetration (k_p) between WPP and WPI. Compared with WPI, reconstituted freeze-dried WPP dispersions did not improve foamability, likely due to slower A-W interface adsorption associated with their larger particle sizes; however, they demonstrated enhanced foam stability, evidenced by a longer 75%-volume lifetime. This improvement is likely attributed to the entrapment of WPP within the lamellae and Plateau borders of foam structure, which may increase local viscosity and block the liquid drainage channels, thereby retarding foam collapse. Moreover, WPP exhibited minimal changes in their PSD and turbidity after heat treatment, suggesting enhanced heat stability relative to WPI.