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Article
Impact of Electrostatic Interactions on Formation and Stability of Emulsions Containing oil Droplets Coated by Beta-Lactoglobulin-Pectin Complexes
Journal of Agricultural and Food Chemistry (2007)
  • Demet Guzey
  • D. Julian McClements, University of Massachusetts - Amherst
Abstract

Interfacial protein−polysaccharide complexes can be used to improve the physical stability of oil-in-water emulsions. The purpose of this study was to examine the impact of ionic strength on the formation and stability of oil-in-water emulsions containing polysaccharide−protein-coated droplets. Emulsions were prepared that contained 0.1 wt % corn oil, 0.05 wt % β-lactoglobulin, and 0.02 wt % pectin at pH 7. The emulsions were then adjusted to pH 4 to promote electrostatic deposition of the pectin molecules onto the surfaces of the protein-coated droplets. The salt concentration of the aqueous phase (0 or 50 mM NaCl) was adjusted either before or after deposition of the pectin molecules onto the droplet surfaces. We found that stable emulsions containing polysaccharide−protein-coated droplets could be formed when the salt was added after pectin adsorption but not when it was added before pectin adsorption. This phenomenon was attributed to the ability of NaCl to promote droplet flocculation in the protein-coated droplets so that the pectin molecules adsorbed onto the surfaces of flocs rather than individual droplets when salt was added before pectin adsorption. We also found that polysaccharide−protein-coated droplets had a much improved stability to salt-induced flocculation than protein-coated droplets with the same droplet charge (ζ-potential). Theoretical predictions indicated that this was due to the ability of the adsorbed polysaccharide layer to strongly diminish the van der Waals attraction between the droplets.

Keywords
  • emulsion,
  • β-lactoglobulin,
  • pectin,
  • multilayer,
  • stability,
  • electrostatic
Disciplines
Publication Date
2007
Publisher Statement
DOI: 10.1021/jf062342f
Citation Information
Demet Guzey and D. Julian McClements. "Impact of Electrostatic Interactions on Formation and Stability of Emulsions Containing oil Droplets Coated by Beta-Lactoglobulin-Pectin Complexes" Journal of Agricultural and Food Chemistry Vol. 55 Iss. 2 (2007)
Available at: http://works.bepress.com/djulian_mcclements/88/