Synergistic stabilization of a clean-label bigel: whey protein isolate constructing dual oleogel/hydrogel networks

This study aims to develop a clean-label bigel by a whey protein isolate (WPI, as the only oleogelator and emulsifier)-based emulsion-mediated strategy, focusing on the effect of oleogel/hydrogel ratios on structural and physicochemical properties of bigel. Aerogel-templated WPI oleogels prepared through freeze-drying and oil-phase reconstitution were homogenized with WPI solutions, followed by thermal induction. The impact of oleogel-to-hydrogel mass ratios (10:90 to 50:50), on emulsion characteristics and bigel properties was investigated. The ratio of WPI solution to oleogel critically modulated bigel microstructure: at low ratios (≤20%), emulsions exhibited monomodal distribution with high electrostatic stability (ζ-potential = −67 mV), whereas higher ratios (>20%) induced bimodal distribution. The incorporation of oleogel led to a redshift and broadening of the N-H stretching vibration peak (3280-3300 cm −1 ). This spectral change (redshift and broadening) suggested enhanced intermolecular hydrogen bonding. A denser three-dimensional network with diminished pore volume was observed as the oleogel ratio increased, suggesting the infiltration of the oleogel phase into the hydrogel matrix. All bigel formulations exhibited solid-like, elastic-dominated mechanical behavior (G' > G″). Increasing the oleogel ratio enhanced the storage modulus (G′), which was attributed to a greater crosslinking density within the composite matrix. This study presents a sustainable strategy for designing clean-label solid fat replacers with tailored physicochemical properties.