Influence of competitive adsorption on flocculation and rheology of high-pressure-treated milk protein-stabilized emulsions.
The effect of high-pressure treatment (HPT) on the droplet-size distribution and small-deformation rheology of oil-in-water emulsions containing beta-lactoglobulin and a nonionic surfactant or sodium caseinate has been investigated at neutral pH. Addition of Tween 20 (polyoxyethylenesorbitan monolaurate) to a beta-lactoglobulin-stabilized emulsion results in competitive displacement of the adsorbed globular protein film and, following HPT, the formation of a less flocculated emulsion. The age of the beta-lactoglobulin-stabilized emulsion prior to addition of sodium caseinate influences the competitive adsorption behavior. The strengthening of the beta-lactoglobulin layer with time makes it more resistant to disruption by sodium caseinate. The level of pressure-induced flocculation of beta-lactoglobulin-coated oil droplets depends on the intensity of processing conditions and on the degree of interfacial displacement. In contrast, beta-lactoglobulin added after emulsification appears to show little evidence of competitive adsorption behavior at the caseinate oil-water interface. Changes in the rheological properties of these latter systems following HPT can be attributed to pressure-induced denaturation and gelation of beta-lactoglobulin in the continuous phase of the emulsion.
Dickinson
E
E
Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, United Kingdom. E.Dickinson@leeds.ac.uk
James
J D
JD
D000327:Adsorption; D004655:Emulsions; D008894:Milk Proteins / Q000737:chemistry*; D011312:Pressure; D012212:Rheology
D004655:Emulsions; D008894:Milk Proteins