Effects of pH on Foam Formation by Whipping in Spray-Dried Egg White Dispersion

Abstract

Three types of spray-dried egg white powders, of which dispersion in water showed pH of 7.4 (EW7.4), 8.4 (EW8.4) and 10 (EW10), respectively, were adjusted to pH 4.0, 7.4 and 9.0. The obtained egg white dispersions were separately whipped to afford foams similar to meringue. Foaminess (specific volume) was highest at pH 4.0 for EW8.4 and EW10, but lowest for EW7.4. From stress-strain curves, three parameters (maximum stress, breakdown and apparent elasticity) were calculated and compared among pH levels adjusted just before whipping. All parameters were lowest at pH 4.0 and showed inhibited foam formation in contrast with foaminess. Thus, EW7.4-whipped foam showed a different pH-dependency from EW8.4 and EW10. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis of insoluble fractions derived from whipped foams, lysozyme was washed out by KCl solution for EW7.4, differing from EW8.4 and EW10, in which lysozyme remained in the insoluble fraction after washing with KCl or water. From the above results, pH adjustment for egg white before spray drying is considered to modify the interaction between egg proteins and to change the physical properties of whipped foam.