Deciphering pH effects on relationships between molecular conformation and interfacial properties of bovine...

This study investigated pH-dependent conformational changes in bovine α-lactalbumin using molecular dynamics simulations of holo and apo forms at pH 3.0, 4.8, and 6.6. Structural integrity was maintained at pH 4.8 and 6.6 (RMSD <3.5 Å), whereas pH 3.0 caused Ca²⁺ depletion at ∼110 ns, increased flexibility (RMSD ∼5.5 Å) and SASA (∼8%), and destabilized h1b and S1-S2 through Asn45-Lys50 rearrangements, increasing amphiphilicity, particularly in Apo-LA. In vitro assays revealed pH-dependent differences in foam capacity and decay despite the absence of significant differences in interfacial tension. The greater conformational flexibility and amphiphilic exposure observed at pH 3.0 provide a molecular interpretation consistent with this foaming behavior, particularly the slower foam decay of Apo-LA. These findings provide a molecular-level basis for tailoring the pH-dependent foaming performance of α-LA-containing formulations, including yogurt-based aerated products, acidic foaming beverages, and blended dairy-plant protein matrices, although validation in multicomponent food systems remains necessary.