Structural and foaming properties of egg albumen subjected to different pH-treatments in the presence of calcium ions

The influence of low (pH 1.5-3.5) and high (10.5-12.5) pH-induced unfolding followed by refolding to pH 4.5-8.5 in the presence of Ca2+ on the structural, functional and viscoelastic properties of egg albumen was investigated. pH-induced unfolding significantly improved overrun, stability and reduced liquid drainage of egg albumen for most pH-treatments compared to untreated control. Unfolding at pH 12.5 led to the largest improvements, overall. Improvements in foam overrun and stability were found to be mostly due to pH-treatments, with Ca2+ having a small effect when compared to prior studies. Inclusion of Ca2+ did however reduce liquid drainage, and was found to significantly modify the theological properties of the foams, making them stiffer and stronger. Inclusion of Ca2+ during pH-treatment led to more exposed -SH groups compared to albumen pH-treated in its absence. The pH-treatments also produced albumens with higher surface hydrophobicity, which was determined mostly to come from the pH unfolding, with Ca2+ having little impact. (c) 2007 Elsevier Ltd. All rights reserved.