Zeta Potential Of Emulsion Droplets Research Articles

Understanding how the properties of whey protein stabilized emulsions depend on pH, ionic strength and calcium concentration, by mapping environmental conditions to zeta potential

Surface properties play a key role in determining how colloidal particles interact. In the case of emulsion droplets stabilized with whey protein isolate (WPI) the repulsive interactions are thought to be mostly electrostatic and governed by the environment-modulated zeta potential of the droplet surfaces. By coupling a Gouy-Chapman model of the electrical double layer with the chemical equilibria of both the ionizable moieties on the protein and of the binding of calcium by charged groups, the zeta potential of emulsion droplets as a function of pH, ionic strength and calcium concentration is predicted. Experimental data is shown to fit well to this model. In addition the zeta potential alone is shown to be a good predictor of the macroscopic behavior of the emulsion, as characterized by measurements of the low-stress viscosity.

Beverage emulsions: Comparison among nanoparticle stabilized emulsion with starch and surfactant stabilized emulsions

Emulsions are widely used in beverages to impart desired appearance and flavor to the products. Ring formation in beverages with emulsions during thermal processing and storage is one of the key challenges. This study was aimed at comparing the relative effectiveness of silica nanoparticle based emulsifiers with surfactant and biopolymer based emulsifier (modified starch) in influencing physical stability of emulsions in a model juice. The stability of emulsions was measured by characterizing changes in emulsion droplet size, zeta potential, UV–vis absorbance and visual evaluation of phase separation or ring formation in both primary emulsions and beverage emulsions as a function of storage time. The influence of thermal processing on stability of emulsions both immediately after processing and upon storage was evaluated. The thermal processing conditions simulated both high temperature short time and low temperature long time pasteurization conditions. The results demonstrate that the mean droplet diameter of primary emulsions stabilized by selected emulsifiers was stable during storage for 21days with and without pasteurization. Based on measurements of mean droplet diameter and visible ring formation, polyoxyethylene sorbitan monolaurate (tween-20) stabilized emulsion was not stable in a model juice and the stability of this emulsion was further reduced with thermal processing. In contrast, starch and silica stabilized emulsions in a model juice did not show significant changes in particle diameter or visible ring formation during storage with and without prior thermal processing, although starch stabilized emulsion did show a decrease in absorbance during storage. Zeta potential measurements in a model juice indicate that the surface properties of emulsions were significantly distinct from those of primary emulsion, indicating interaction of juice components with the emulsion interface influencing the surface charge at the interface. These changes in zeta potential of emulsion droplets did not correlate with reduced stability of the emulsions. Overall, the results demonstrate that nanoparticle stabilized emulsions can improve stability of emulsion in beverages as compared to surfactant and biopolymer stabilized emulsions and provides a comprehensive matrix to evaluate stability of emulsions in beverages.

Emulsification of heavy crude oil in water by natural surfactants

The factors affecting the stability of a heavy crude oil-in-water emulsion stabilized by sodium carbonate (Na2CO3) as a natural surfactant were studied. An Iranian heavy crude oil, namely West Paydar, was used as the oil phase of the emulsions. Tap water was used as the aqueous phase. Various concentrations of sodium chloride were employed to study the effect of aqueous phase salinity on the stability and interfacial tension of the emulsions. The stability and viscosity of O/W emulsions and their viability for the transportation of heavy crude oil through the pipeline were investigated. The diverse factors affecting the properties of emulsions were investigated.The study reveals that the stability of the oil-in-water emulsions was increased versus surfactant concentration due a decrease in the crude oil–water interfacial tension. The natural surfactant was responsible for the very low values of interfacial tensions observed and for the stabilization of the viscous crude oil-in-water emulsions. By increasing the surfactant concentration in the aqueous phase, as well as the speed and duration of homogenization, the emulsion stability was increased. There was a limit of 60vol.% for the crude oil content in the emulsions, beyond that the emulsions were inverted into water-in-oil emulsions. Zeta potential measurements revealed that the zeta potential of emulsion droplets decreased by the concentration of sodium carbonate in the aqueous phase.

Effects of amine and amine oxide compounds on the zeta-potential of emulsion droplets stabilized by phosphatidylcholine

A positively charged submicron emulsion based on phospholipid was suggested and their surface electrical properties were investigated at various pHs. Additives used to change the zeta potential of emulsion were decyldimethylamine oxide (DeDAO), dodecyldimethylamine oxide (DDAO) stearylamine (SA) and dodecylamine (DA). Also the emulsion droplet size and size distribution were measured to study the effects of additives on the emulsion properties. By adding additives, the zeta potential of emulsion droplet has been significantly changed but there were little effects on emulsion size and size distribution. In a wide range of pH (≈8.0), all additives yielded the positive zeta potential values. But at pH 10, amine compounds generated the negative-charged emulsion droplets while amine oxide compounds generated the neutral emulsion droplet. From this study, it was found that amine oxide compounds as well as amine compounds can be used to modify the zeta potential of emulsion droplets from negatively charged to positively charged below pH 8.0 for the effective drug delivery vehicles.

Physico-Chemical Properties of Monodesmoside Saponins of Sapindaceae(Sapindus mukurossi Gaertn) at Air/Water and Oil/Water Interfaces.

The surface activity, emulsion stability and foamability for two kinds of monodesmoside saponins of Sapindus mukurossi Gaertn (I and II) and the zeta potentials of emulsions prepared with these saponins in a water/kerosene system were investigated. There were no differences in the surface activity, foamability, emulsion stability or zeta potential of the emulsion droplet between the two kinds of saponins (I and II) of sapindaceae. The surface activity, emulsion stability and foamability of both I and II were higher than those of soyasaponin I (SI). The zeta potential of emulsion droplets prepared with I or II was lower than that prepared with SI. The water separation of both the I and II emulsions by creaming were higher than that of the SI emulsion.

The zeta potential of emulsion droplets of the aliphatic hydrocarbons in aqueous solutions

This paper includes the results of investigations of the zeta-potential changes of emulsion droplets of hydrocarbons (n-alkanes containing 9 to 16 carbon atoms in hydrocarbon chains) depending on the pH of aqueous solutions. The zeta potential of emulsion droplets of hydrocarbons was determined from measurements of electrophoretic velocity observed on a TV monitor screen. The results indicated that the zeta potential of emulsion droplets is a function of pH and does not depend on the chain-length of the investigated aliphatic hydrocarbons. A distinct correlation between the values of the zeta potential and the separation velocity of the amount of the hydrocarbon liquid phase on the aqueous solution surface was observed. The effectiveness of the process gradually increases together with the linear drop to zero zeta potential in the acid solutions.

The zeta potential of emulsion droplets of the aliphatic hydrocarbons in aqueous solutions

This paper includes the results of investigations of the zeta-potential changes of emulsion droplets of hydrocarbons (n-alkanes containing 9 to 16 carbon atoms in hydrocarbon chains) depending on the pH of aqueous solutions. The zeta potential of emulsion droplets of hydrocarbons was determined from measurements of electrophoretic velocity observed on a TV monitor screen. The results indicated that the zeta potential of emulsion droplets is a function of pH and does not depend on the chain-length of the investigated aliphatic hydrocarbons. A distinct correlation between the values of the zeta potential and the separation velocity of the amount of the hydrocarbon liquid phase on the aqueous solution surface was observed. The effectiveness of the process gradually increases together with the linear drop to zero zeta potential in the acid solutions.