Direct oil structuring using engineered whey protein particles: Rheological characterization and application in...

Whey protein-based oleogels have emerged as promising fat replacers in food applications, but current fabrication strategies predominantly rely on indirect approaches involving complicated processing steps and undesirable solvents. To address this challenge, whey protein particles can be engineered as effective gelators capable of directly structuring liquid oils into functional oleogels. This study engineered whey protein hydrogel particles (WPHP) and microgel particles (WPMP) through pH modification (5.0/5.7) and thermal treatment. The resulting particles exhibited lower bulk density and improved porosity compared to whey protein isolate (WPI), forming interconnected networks rather than discrete particulate structures. Using a one-step process, sunflower oil (30-70 %, w/w) was directly incorporated into protein particle matrices to form structured oleogels, resulting in oleogels transitioned from solid to fluid-like states as the oil content increased. A critical semi-solid creamy texture was identified at 60 % oil content and selected for further testing. Particle-based oleogels exhibited greater elasticity and deformation resistance compared to the WPI-based control, as demonstrated by the small and large amplitude oscillatory shear (SAOS/LAOS) rheology. When incorporating oleogels into chocolates (50 % cocoa butter replacement), the oleogel-based formulation exhibited elevated melting points and significantly reduced hardness compared to the regular chocolate. Additionally, under simulated oral conditions (with mixed saliva), oleogel-based chocolates demonstrated significantly lower friction coefficients, indicating improved lubrication and smoother mouthfeel. These findings establish engineered whey protein particles as effective oleogelators, which enables a direct, solvent-free strategy to formulate structured oleogels for developing reduced-fat chocolate as a functional cocoa butter alternative.