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This study aims to evaluate monovalent (Na+) and divalent (Mg2+) ions regulated ovalbumin (OVA) foaming properties enhancement via the change of protein structural and interfacial properties. The macro and microscopic photographs of samples after homogenization 0 min and 30 min were recorded. Results showed that foaming capacity (FC) significantly increased from 59.44 ± 16.69% to 136.67 ± 11.55% (NaCl) and 117.22 ± 5.36% (MgCl2). Accordingly, viscosity and surface intension reduced, whereas the amount of OVA adsorption increased, which suggested that ions could promote adsorption of OVA to air-water interface and further improve the foaming properties. Analogously, surface hydrophobicity (H0) increased, which revealed that the improvement of hydrophobic interactions of OVA. Besides, the β-sheet content increased, which indicated larger aggregates formed. Noteworthy, from the results of the interfacial adsorption amount and microscopic photographs, the foaming stability (FS) of samples with divalent ions was better, which could be hypothesized that protein intermolecular interactions via salt bridge may be stronger, while monovalent ions interacted with protein by nonspecific bond. Overall, our study provides a convenient approach of ions regulated structural and foaming properties of OVA, which may be a new strategy in improving the protein interfacial properties in food processing industry.

We report the wet-state glycation of Bovine Serum Albumin (BSA) with xylose through the Maillard reaction and its effect on protein aggregations during heat treatment. Using low doses of xylose, glycation stabilized the conformations of BSA and reduced the formation of large aggregates during heat treatment. However, using high doses of xylose, glycation promoted the conversion of α-helices to unfolded structures and β-sheets, and induced the formation of short amyloid-like aggregates after heat treatment. Using high-resolution mass spectrometry, three possible glycation sites were determined on BSA treated with low dose of xylose, while six glycations sites were detected when high doses of xylose were used instead. Considering the importance of glycation to the food industry, this work not only provides new insights into the nonlinear effects of glycation on protein stability, but also provides a strategy to tune the nutritional value and functionality of proteins during food processing.

Metal ions perform a wide variety of functions associated with life processes. In this work, we investigated the influence of Mg2+ on the denaturation and aggregation of bovine serum albumin (BSA) during heat treatment. The unfolding and denaturation of proteins during food processing, especially heat treatment, has a major influence on their functional properties. Our results show that Mg2+ significantly stabilized the secondary structure of BSA when the protein was heated at 80 °C, preventing the transformation of α-helices into unfolded structures. Mg2+ also inhibited the aggregation of BSA into larger, heterogeneous structures. Moreover, after adding Mg2+, the melting temperature of BSA increased from 70.20 °C to 73.74 °C, further indicating that Mg2+ has a stabilizing effect. Finally, molecular dynamics (MD) simulations revealed that Mg2+ preferentially binds multivalently to the carboxylate groups of Asp and Glu BSA residues, and the observed stabilizing effect could be attributed to the crosslinking of secondary structure elements within BSA induced by Mg2+ binding. Considering the ubiquity of Mg2+, our work provides a facile strategy to control BSA unfolding and aggregation, which is helpful for enhancing the processing and storage properties of BSA or other proteins during food processing.