Flocculation of Whey Protein Stabilized Emulsions as Influenced by Dextran Sulfate and Electrolyte

Abstract

The creaming stability and viscosity of oil-in-water emulsions stabilized by whey protein isolate were monitored as functions of dextran sulfate (DS) and electrolyte (NaCl) concentration. At a specific DS concentration (the critical flocculation concentration, CFC), the droplets became flocculated, which promoted creaming. Addition of electrolyte caused an increase in CFC. At NaCl concentrations Ͻ0.5 wt%, addition of electrolyte decreased emulsion viscosity, but at concentrations Ͼ0.5 wt% it caused an increase in viscosity due to increased flocculation. The results were due to the influence of electrostatic screening on the effective volume of DS molecules and colloidal interactions between droplets.

New insights into the study of the destabilization of oil-in-water emulsions with dextran sulfate provided by the use of light scattering methods

“…The intrinsic viscosity of this sample of dextran sulfate prepared in aqueous solvent with 0.28 wt % of NaCl was found to be equal to 2.2 ± 0.2 dL g À1 . This result was in accordance with data reported by Demetriades and McClements (1999).…”

“…They did not interact with dextran sulfate, they repelled each other and induced sufficient highly-repulsive forces to overcome the attractive force that could be induced by the steric-exclusive osmotic depletion forces of DS. Moreover, it was reported that the increase in NaCl concentration reduced the degrees of depletion and Van der Waals attractions (Demetriades & McClements, 1999). In good agreement with these results, an increase in NaCl to 0.78wt % reduces by two times the intrinsic viscosity of dextran sulfate.…”

“…Afterwards this level didn't increase but the height of the cream layer decreased from 24 to 17 mm at 24 h. It evidenced the collapse of a network. On the contrary, Demetriades and McClements (1999) demonstrated that a WPC-stabilized emulsion was stable upon creaming for 24 h when DS was added at a concentration higher than 2%. They added DS after preparing the protein-stabilized emulsion.…”

Prebiotic emulsions stabilised by whey protein and kefiran

“…Thus, the strengthening of the structure takes place probably due to a thickening of the continuous phase as the kefiran concentration is increased. However, the presence of the polysaccharide might also induce a depletion process promoting protein aggregates interactions (Demetriades & McClements, 2006). The presence of a certain amount of polysaccharide in an emulsion system may cause depletion flocculation (Dickinson, 2019).…”

Expanded Functionality of Modified Whey Protein Dispersions after Transglutaminase Catalysis

“…Creaming index. The creaming index, a measure of emulsion stability, was assessed according to the method of Demetriades and McClements (1999). For these experiments, 10 mL volume of each emulsion were delivered into a 15-mL marked tube and stored for the specified time intervals at ambient temperature.…”