pH-dependent structural properties, air–water interfacial behavior, and foam stability of fibrillated egg white protein

Acid heating converted EWP into fibrillar aggregates. • pH regulated aggregation and structural evolution of F-EWP. • Fibrillated EWP improved air-water interfacial adsorption. • pH 5 promoted foaming capacity and long-term foam stability. Fibrillation is an effective approach for enhancing the interfacial functionality and foam stability of egg white protein (EWP). However, the highly acidic conditions commonly used for fibril formation are incompatible with the pH ranges of most practical food systems, and the pH-shift-induced structural evolution and foam stabilization behavior of whole fibrillated egg white protein (F-EWP) remain poorly understood. Herein, acid–heat-induced F-EWP was prepared and compared with EWP adjusted to identical pH values to elucidate the effects of pH on protein structural evolution, interfacial adsorption, and foaming behavior. Acid–heat treatment converted EWP from its native globular conformation into a β-sheet-enriched fibrillar structure. Subsequent pH modulation further reshaped the structural features, interfacial adsorption characteristics, and foaming performance of F-EWP. Relative to EWP, F-EWP consistently exhibited lower dynamic interfacial tension, higher interfacial pressure, and superior foaming properties across all tested pH conditions. Foam rheology and microstructural observations further revealed that the improved foam stability of F-EWP was primarily associated with enhanced foam viscoelasticity, a finer bubble architecture, and more efficient retention of the liquid phase within the lamellae and Plateau borders. Notably, F-EWP at pH 5 showed local aggregation/entanglement and conformational rearrangement, accompanied by low interfacial tension and high K p (−5.19 × 10 −2  ± 0.47) and K r (−4.67 × 10 −2  ± 0.03), resulting in the highest FA and foam stability of 207.3 ± 12.46% and 74.67 ± 6.12%, respectively. These findings provide a mechanistic basis for broadening the application of F-EWP in pH-variable food foam systems. Download: Download high-res image (468KB) Download: Download full-size image