Characterization of food colloids by phase analysis light scattering

Recently a novel technique, phase analysis light scattering (PALS), has been developed to measure the electrophoretic mobility of charged particles that offers enhanced sensitivity at the low mobilities, typical of many food colloids. The principles of this technique are discussed in comparison to conventional laser Doppler electrophoresis (LDE). A sample of whey protein isolate solution (10 wt%) was titrated with HCl (0.1 M) and the electrophoretic mobility measured by PALS and LDE. Both methods showed an increase in electrophoretic mobility with pH, but PALS yielded better reproducibility. In addition, PALS could be used to measure the isoelectric point of the protein mixture as the pH where the mobility was zero.