A diffusing wave spectroscopy study of the dynamics of interactions between high methoxyl pectin and sodium caseinate emulsions during acidification.
A non-invasive technique, diffusing wave spectroscopy (DWS), and traditional dynamic light scattering (DLS) were used to study the interactions of high methoxyl pectin (HMP) with sodium caseinate-stabilized emulsion droplets. At pH 6.8, the droplet size measured by DLS did not change as a function of HMP concentration (up to 0.3%). However, the droplet diameter measured by DWS kept relatively constant up to 0.07% HMP after which it showed drastic increases. The turbidity parameter 1/l* decreased with HMP concentration and levelled off at 0.07% HMP, indicating that the system underwent reorganization and reached equilibrium at 0.07% HMP. During acidification at pH 5.4, right before the pH of aggregation of control emulsions, all emulsions containing 0.05-0.2% HMP showed an increase of 1/l*. This increase indicated the interaction of HMP with sodium caseinate at the interface. Emulsions containing 0.05 and 0.1% HMP also showed destabilization, and the pH of destabilization depended on the concentration of HMP. Sufficient amounts of HMP (0.2%) stabilized the caseinate-coated oil droplets, and the mean square displacement slope was close to 1 throughout, indicating free diffusion of emulsion droplets.
Liu
Jinru
J
Department of Food Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Corredig
Milena
M
Alexander
Marcela
M
D002364:Caseins / Q000737:chemistry*; D004655:Emulsions; D006863:Hydrogen-Ion Concentration; D008027:Light; D010368:Pectins / Q000737:chemistry*; D012542:Scattering, Radiation; D013057:Spectrum Analysis
D002364:Caseins; D004655:Emulsions; D010368:Pectins