Heteroprotein complex coacervation of ovalbumin and lysozyme: Phase behavior, microstructure and processing properties

Egg white protein is a complex network system formed by the aggregation and interaction of multiple proteins, in which two oppositely charged proteins can induce the formation of heteroprotein complex coacervate (HPCC). This investigation aims to probe the complexation between ovalbumin (OVA) and lysozyme (LYS) via the heteroproteins phase diagram model, exploring the relationship between differential processing properties and complex state, protein molecular structure and intermolecular interactions. Results showed that the characteristic pH (pHc, pHɸ1, pHmax, pHɸ2) intensely relied on the protein ratios. Consequences of ζ-potential and the phase diagram manifested that OVA-LYS complex formation was predominantly triggered by electrostatic interactions. With the increasing OVA-LYS mixing ratio, the characteristic pH of the complex moved towards a higher pH value. By comparing the microphase structure of different phase regions induced by pH, we found that the protein structure unfolded at low pH, elevating the foaming and emulsifying capacity. Moreover, further increases in pH value brought on larger insoluble complex formation, which enhanced the foaming stability while decreased the emulsifying stability. Noteworthy, the coacervates obtained in the narrow range of pH 6.5–9.5 presented the strongest gel strength and highest water holding capacity, which was considered to be an efficacious way to regulate the gel properties of egg white protein. On the whole, the findings of this paper developed prominent insight for understanding the interaction between heteroproteins, which would lay a theoretical foundation for improving the quality and efficiency of functional egg powder and product development.