Comparison of Different Mechanical Methods for the Modification of the Egg White Protein Ovomucin, Part A: Physical Effects

Abstract

It is indispensable to modify the physical properties of egg white prior to a fractionation of the included bio-functional proteins. It was already demonstrated that this can be realized with mechanical devices. However, until now, it was not clear by which kind of molecular changes this is accompanied. Thus, this study reports on the molecular changes in egg white proteins induced by various mechanical treatments (high-pressure homogenizer, colloid mill, toothed disc dispersing machine). Evaluation criteria were the particle size of the long-chain protein ovomucin, the content of thiol groups, and disulfide bridges in egg white as well as the amount of free lysozyme. In general, it was shown that these treatments led to changes in the molecular structure and that the obtained modifications were more pronounced the higher the applied energy was. In detail, it was found that the applied mechanical forces in the experimental range of this study were able to disrupt strong covalent bonds in the fibrillar protein ovomucin. Additionally, the bio-functional protein lysozyme that is partly entrapped in the natural egg white structure was released by the applied forces. Summing up, this study generates comprehensive knowledge concerning the underlying mechanisms that enable the release of lysozyme as well as the use of egg white for fractionation processes.