Manipulating and quantifying temperature-triggered coalescence with microcentrifugation
Feng Huanhuan, Huanhuan ; Ershov, D.S. ; Krebs, T. ; Schroën, C.G.P.H. ; Cohen Stuart, M.A. ; Gucht, J. van der; Sprakel, J.H.B. - \ 2015
Lab on a Chip 15 (2015)1. - ISSN 1473-0197 - p. 188 - 194.
disjoining pressure - droplet formation - emulsions
In this paper we describe a new approach to quantify the stability and coalescence kinetics of thermally switchable emulsions using an imaging-based microcentrifugation method. We first show that combining synchronized high-speed imaging with microfluidic centrifugation allows the direct measurement of the thermodynamic stability of emulsions, as expressed by the critical disjoining pressure. We apply this to a thermoresponsive emulsion, allowing us to measure the critical disjoining pressure as a function of temperature. The same method, combined with quantitative image analysis, also gives access to droplet-scale details of the coalescence process. We illustrate this by measuring temperature-dependent coalescence rates and by analysing the temperature-induced switching between two distinct microscopic mechanisms by which dense emulsions can destabilise to form a homogeneous oil phase.
Effect of Glycation on the Flocculation Behavior of Protein-Stabilized Oil-in-Water Emulsions
Delahaije, R.J.B.M. ; Gruppen, H. ; Nieuwenhuijzen, N.H. van; Giuseppin, M.L.F. ; Wierenga, P.A. - \ 2013
Langmuir 29 (2013)49. - ISSN 0743-7463 - p. 15201 - 15208.
bovine serum-albumin - beta-lactoglobulin - physicochemical properties - adsorption dynamics - disjoining pressure - alpha-lactalbumin - interfaces - particles - thickness - size
Glycation of proteins by the Maillard reaction is often considered as a method to prevent flocculation of protein-stabilized oil-in-water emulsions. The effect has been suggested, but not proven, to be the result of steric stabilization, and to depend on the molecular mass of the carbohydrate moiety. To test this, the stabilities of emulsions of patatin glycated to the same extent with different mono- and oligosaccharides (xylose, glucose, maltotriose, and maltopentaose) were compared under different conditions (pH and electrolyte concentration). The emulsions with non-modified patatin flocculate under conditions in which the zeta potential is decreased (around the iso-electric point and at high ionic strength). The attachment of monosaccharides (i.e., glucose) did not affect the flocculation behavior. Attachment of maltotriose and maltopentaose (Mw > 500 Da), on the other hand, provided stability against flocculation at the iso-electric point. Since the zeta potential and the interfacial properties of the emulsion droplets are not affected by the attachment of the carbohydrate moieties, this is attributed to steric stabilization. Experimentally, a critical thickness of the adsorbed layer required for steric stabilization against flocculation was found to be 2.29–3.90 nm. The theoretical determination based on the DLVO interactions with an additional steric interaction coincides with the experimental data. Hence, it can be concluded that the differences in stability against pH-induced flocculation are caused by steric interactions.
Protein Concentration and Protein-Exposed Hydrophobicity as Dominant Parameters Determining the Flocculation of Protein-Stabilized Oil-in-Water Emulsions
Delahaije, R.J.B.M. ; Wierenga, P.A. ; Nieuwenhuijzen, N.H. van; Giuseppin, M.L.F. ; Gruppen, H. - \ 2013
Langmuir 29 (2013)37. - ISSN 0743-7463 - p. 11567 - 11574.
diffusing wave spectroscopy - beta-lactoglobulin - coalescence stability - disjoining pressure - drop size - adsorption - films - ph - interfaces - ovalbumin
DLVO theory is often considered to be applicable to the description of flocculation of protein-stabilized oil-in-water emulsions. To test this, emulsions made with different globular proteins (ß
Influence of NaCl on the behavior of PEO-PPO-PEO triblock copolymers in solution, at interfaces, and in asymmetric liquid films
Eliseeva, O.V. ; Besseling, N.A.M. ; Koopal, L.K. ; Cohen Stuart, M.A. - \ 2005
Langmuir 21 (2005)11. - ISSN 0743-7463 - p. 4954 - 4963.
oxide) block-copolymer - aqueous-solution - nonionic surfactant - foam films - cationic surfactants - air/water interface - disjoining pressure - water/air interface - protein adsorption - micellization
The solution behavior of the polymeric surfactant Pluronic F127 (PEO 99PPO65PEO99) and its adsorption behavior on aqueous - silica and aqueous - air interfaces, as well as the disjoining pressure isotherms of asymmetric films (silica/aqueous film/air) containing F127, are studied. The interfacial properties of adsorbed F127 layers (the adsorbed amount ¿ and the thickness h) as well as the aqueous wetting film properties [film thickness (h) and refractive indexes] were studied via ellipsometry. The solution properties of F127 were investigated using surface tensiometry and light scattering. The interactions between the air -water and silica - water interfaces were measured with a thin film pressure balance technique (TFB) and interpreted in terms of disjoining pressure as a function of the film thickness. The relations between the behaviors of the asymmetric films, adsorption at aqueous air, and aqueous silica interfaces and the solution behavior of the polymeric surfactant are discussed. Special attention is paid to the influence of the concentrations of F127 and NaCl. Addition of electrolyte lowers the critical micelle concentration, diminishes adsorption on silica, and increases the thickness of the asymmetric film.