Thermostable conformational transition unfavorable to the foaming stability of ovalbumin: Emphasizing structure and function relationship

Storage of shell eggs converts natural ovalbumin (N-OVA) into its more thermostable forms (S-OVA). This conversion may be associated with deterioration in the foaming properties of the stored shell egg. Thus, the foaming behavior of N-OVA and S-OVA, especially their performance at different pH conditions, was conducted. Compared with N-OVA, S-OVA improved foaming ability by 29.04 % at pH 3.0 and exhibited rough foam. Regarding foaming stability, the conversion of N-OVA to S-OVA had a pronounced reduction effect, with foaming stability significantly decreasing by 28.48 %-100.00 % in pH 3.0-9.0. The spectroscopic analysis revealed that the alteration in the foaming properties of OVA was fundamentally attributed to its conformational change. Thermostable conformational transition provided S-OVA with smaller particle sizes, more flexible conformations, higher surface charge, and higher surface hydrophobicity. S-OVA at pH 3.0 showed a higher surface activity, indicating superior foaming ability. Moreover, N-OVA and S-OVA formed stiff and solid-like interfaces. Notably, N-OVA exhibited higher dilatational and elastic modulus, indicating a more compact and stable adsorption layer at air-water interface. Overall, thermostable conformational transition improved the interfacial activity of OVA and enhanced its foaming ability; however, overactive proteins were detrimental to the stabilization of its interfacial films.