Rheological Behavior Of Emulsions Research Articles

Ferrofluid droplets in planar extensional flows: Droplet shape and magnetization reveal novel rheological signatures of ferrofluid emulsions

By subjecting a ferrofluid emulsion to an external magnetic field, the flow at the droplet scale is altered, resulting in significant changes in the emulsion's rheological behavior. We present the first study of the rheological response of a dilute ferrofluid emulsion under extensional flow. Our findings reveal that at the microscopic level, the droplets experience a field-induced internal torque that leads to a complex non-symmetric stress tensor. We identify the remarkable presence of shear stresses within a material experiencing a pure extensional flow.

Rancidity-induced protein oxidation affects the interfacial dynamic properties and the emulsion rheological behavior of rice bran protein

To improve the practical application of rice bran protein (RBP) prepared from rice bran (RB) with different degrees of rancidity as a stabilizer in emulsion, fresh RB was stored for 0, 1, 5, 7, and 10 d (temperature of 25 °C, relative humidity of 85%) to investigate the effects of RB rancidity on the interfacial dynamic properties and structures of RBP, rheological properties of the O/W emulsion prepared by RBP. RB rancidity-induced moderate oxidation of RBP (prepared from RB storage for 1 d) reduced the particle size (24.36–18.17 nm) and Zeta potential (−13.57 ∼ −14.97 mV) of RBP, while excessive RBP oxidation (prepared from RB storage for 5–10 d) increased the particle size (37.84–68.06 nm) and Zeta potential (−13.40 ∼ −10.6 mV) of RBP. In addition, moderate protein oxidation increased the interfacial pressure, diffusion rate, interfacial expansion modulus of RBP, and emulsion viscoelasticity, while excessive protein oxidation improved the permeability rate and rearrangement rate of RBP. Overall, this study demonstrated that moderate protein oxidation had positive effects on interfacial properties (interfacial dynamic properties and dilatational rheology of interfacial layers) of RBP, which could provide a theoretical basis for mediating the stability and rheology of RBP emulsions by adjusting the degrees of RB rancidity. • Rancidity-induced RBP oxidation changed the K diff , K p and K r of RBP. • RBP oxidation changed the viscoelasticity of interfacial adsorption layers. • RBP oxidation changed the viscosity, G′ and G″ of RBP emulsions.

Rheology of Emulsions Thickened by Starch Nanoparticles.

The rheology of oil-in-water (O/W) emulsions thickened by starch nanoparticles is investigated here. The starch nanoparticle concentration is varied from 0 to 25 wt% based on the matrix aqueous phase. The oil concentration is varied from 0 to 65 wt%. At a given nanoparticle concentration, the emulsions are generally Newtonian at low oil concentrations. The emulsions become shear-thinning at high oil concentrations. The increase in nanoparticle concentration at a given oil concentration increases the consistency of the emulsion and enhances the shear-thinning behavior of emulsion. The rheological behavior of emulsions is described reasonably well by a power-law model. The consistency index of the emulsion increases with the increases in nanoparticle and oil concentrations. The flow behavior index of emulsion decreases with the increases in nanoparticle and oil concentrations, indicating an increase in the degree of shear-thinning in emulsion.

Characterization of clay-stabilized, oil-in-water Pickering emulsion for potential conformance control in high-salinity, high-temperature reservoirs

In this study, a Na-montmorillonite clay-stabilized, oil-in-water (O/W) Pickering emulsion system was prepared and tested under high-salinity and high-temperature conditions. The emulsifying ability of the clay particles, emulsion stability against creaming and coalescence, and emulsion rheological behavior at different NaCl concentrations and temperatures were investigated. The results showed that decane could be effectively emulsified by clay particles into small emulsion droplets at salinities up to 25 wt% NaCl. The emulsion had a relatively narrow drop size distribution. However, the emulsion stability against creaming decreased with increases in NaCl concentration. At low NaCl concentrations, clay particles connected with each other by edge-edge and edge-face interactions, forming a three-dimensional network that stabilized the emulsion against creaming. A higher concentration of NaCl caused some clay particles to connect through face-face interactions, forming clay clusters. At high NaCl concentrations, the temperature had only a slight effect on the emulsion stability against creaming. However, emulsion stability against coalescence decreased with increasing temperature due to increased droplet collision caused by Brownian motion. A higher concentration of NaCl moderated this temperature effect of coalescence. The viscosity of emulsion decreased with increased NaCl concentration. Temperature increases caused emulsion viscosity to decrease at low NaCl concentration conditions. When the NaCl concentration was higher than 10 wt%, the temperature had little effect on the viscosity. In summary, this study identifies an O/W Pickering system with the potential for conformance control in high-salinity and high-temperature reservoirs.

Stable and bioactive W/O/W emulsion loaded with “Pitanga” (Eugenia uniflora L.) leaf hydroethanolic extract

“Pitanga” leaf hydroethanolic extract (PLHE) presents high antioxidant and antimicrobial activities. The encapsulation of this extract in W/O/W double emulsions could protect its bioactive properties. The objective of this research was to encapsulate PLHE in the inner W phase of a double emulsion and analyze the emulsifiers concentrations and phase ratios effects on its droplet size and the physical stability. Moreover, the double emulsion rheological behavior, antioxidant and antimicrobial activities in their more stable formulation was investigated. For comparison purpose, antioxidant and antimicrobial activities of the PLHE was also determined. Overall, the droplet size and stability were affected by the concentration of emulsifiers and phase ratios. The double emulsion presented heterogeneous droplet size, good physical stability and non-Newtonian behavior. PLHE presented high antioxidant and antimicrobial activities, which was maintained after processing to encapsulation into double emulsion. In conclusion, it was possible to produce active and stable double emulsion loaded with PLHE.

The effects of pectin and wax on the characteristics of oil-in-water (O/W) emulsions.

The study was aimed to investigate characteristics of emulsion containing pectin, wax, maltodextrin, and carotenoid enriched flaxseed oil by means of stability, rheology, particle size, and low-resolution of time domain nuclear magnetic resonance (NMR) relaxometry measurements. Emulsions were prepared with different carotenoid enriched-flaxseed oil concentrations (6%, 9%, 12%, and 15% w/w) and ratios of maltodextrin/(pectin+wax) (3:1, 6:1, 9:1, and 12:1g/g). Percentage separation of 12% oil 12:1 ratio of maltodextrin/(pectin+wax) (g/g), 15% oil 9:1, and 12:1 ratios of maltodextrin/(pectin+wax) (g/g) of emulsions was determined as 2.0 ± 0.5%,4.0 ± 0.5%,and 8.0 ± 0.5%,respectively. No separation was observed in other emulsions. The rheological behavior of emulsions was best described by the power law model. When the concentration of pectin+wax in the emulsion decreased, the n values of the emulsions were close to 1, indicating that the fluid behavior approaches Newtonian behavior. Moreover, the emulsion viscosity was observed to increase when pectin and wax concentrations in the emulsion increased. The increase in pectin and wax concentration in emulsions with oil contents of 6% and 9% resulted in a reduction in the average particle size. However, if the oil concentration in the emulsions was 12% or more, the increase in the ratio of maltodextrin/(pectin+wax) (g/g) led to a decrease in the average particle size. NMR transverse relaxation times (T2 ) of emulsions were measured and results showed that T2 values for almost all formulations decreased when the ratio of maltodextrin/(pectin+wax) reduced. PRACTICAL APPLICATION: Study results demonstrated that the combination of pectin and wax together with maltodextrin as a filling material could be an alternative way to improve emulsion stability. Findings of this study provided useful guidance for the future studies about the potential use of pectin, wax, and maltodextrin as wall material in encapsulation of oils or in producing edible films.

The Rheometric Analysis of the Polymer Modifier's Properties in the Environment of Hydrated Cement.

This paper investigates the effect of polymer modifiers (re-dispersible powder, multifunctional additives, methylhydroxyethylcellulose) on the rheological behavior of emulsions, saturated of calcium hydrosilicates to simulate a hydrating cement structure. The subjects of the study were modified emulsions which had varied concentrations of each additive and they were examined comparatively to a base emulsion. Tests were performed with a CR-rheometer (“Himpribor-1”, Tula, Russia) applying the Searle measuring principle at various shear rates to characterize viscosity properties. The performance of modified mixtures within the operating period was analyzed by using two parameters—effective viscosity (η) and the proportion of structural failure (|m|). The test results showed that the most important factor influencing rheological characteristics is the addition of methylhydroxyethylcellulose additive—the higher additive amount in the emulsion, the higher the viscosity. Furthermore it was noted in the work that adding olefin sulfonate sodium salt causes reduced viscosities as well as lower shear moduli. If ethylhydroxyethylcellulose and ethylene vinyl acetate additives are used in the same mixture together, the rate of structural failure |m| can be relatively similar and low regardless of whether the mixture has large or small viscosity values.

Electrostatic Interaction between Soy Proteins and Pectin in O/W Emulsions Stabilization by Ultrasound Application

Proteins and polysaccharides can play the part of emulsifiers and stabilizers, yet emulsions stabilization may be improved through a protein:polysaccharide complexation based on electrostatic interactions. The chosen homogenization method and the protein:polysaccharide ratio at an adequate pH may affect complexation and its ability as an emulsion stabilizer. We evaluate the effects of ultrasound homogenization and soy protein isolate (SPI) and high methoxyl pectin (PEC) ratio to generate protein:polysaccharide complexes by electrostatic interactions. Moreover, emulsions stabilized by SPI:PEC complexes with 5, 10, 15 % soybean oil contents were evaluated after sonication to assess emulsions stability improvements. SPI and PEC showed strong interaction at pH 3.5, with higher complexation at higher protein ratio (4:1). Sonication reduced complex particle size, creating homogeneous and shear-thinning systems. SPI:PEC 1:1 emulsions had Newtonian behavior, smaller droplets, and remained stable for seven days. At SPI:PEC ratio of 4:1 emulsions had shear-thinning behavior, yet larger droplets and high creaming indexes, thus indicating destabilization by gravitational separation with cream phase and showing droplets with bimodal distribution (1.3-200 μm). Through heating-cooling ramps, temperature effect on rheological behavior of emulsions and pure biopolymers was assessed. 4:1 emulsions showed rheological behavior with a predominant effect of SPI, whereas 1:1 emulsions predominantly showed pectin characteristics. Emulsion stability was greatly affected by SPI:PEC ratio, since the pectin proportion had a strong influence on the emulsions behavior. Moreover, sonication was a fundamental parameter to increase SPI:PEC complexes effectiveness as emulsion stabilizers and use these systems to formulate foods with low oil contents.

Effect of Incorporation of Multiwalled Carbon Nanotubes on the Microstructure and Flow Behavior of Highly Concentrated Emulsions.

Multiwalled carbon nanotubes (MWCNTs) were incorporated into highly concentrated water-in-oil emulsions with the ultimate aim of achieving a uniform and effective dispersion of MWCNTs within the emulsion matrix. The emulsion was formulated in such a way, wherein the internal phase consists of higher than 90 wt %. By keeping the same aqueous-to-oil phase ratio, the amount of MWCNTs in the oil phase was systematically adjusted to investigate their effects on the microstructure development and rheological behavior of the emulsion. The addition of MWCNTs led to a reduced droplet size and also resulted in a narrower distribution of the droplet size. The rheological behavior of nanotube-incorporated emulsions was characterized with varying MWCNT concentrations and also as a function of the emulsification time. The rheological characteristics of the nanotube-incorporated emulsions were identical to those of the neat emulsion and were primarily governed by the variation in the droplet size and droplet-size distribution. However, the yield strain and cross-over strain were independent of the mean droplet size and polydispersity of the emulsion. Emulsions that have smaller droplets exhibited higher storage modulus (G′), yield stress (τY), and apparent viscosity (η). For all refining times investigated, nanotube-incorporated emulsions have higher G′, τY, and η values when compared to the neat emulsion, and these values further increased with the MWCNT concentration. This was primarily due to the decrease in the droplet size with MWCNT addition. Furthermore, our findings suggest that the incorporated MWCNTs did not induce any significant change in the rheological behavior of emulsions with identical droplet sizes, and it remained essentially unchanged with the concentration of MWCNTs. However, the nanotube-incorporated emulsions possessed solidlike behavior up to a higher applied stress when compared to a neat emulsion of identical droplet size.

INFLUENCE OF PROCESSING PARAMETERS ON RHEOLOGICAL BEHAVIOR OF BENTONITE-BASED PICKERING EMULSION

The aim of this work is to study the impact of processing parameters on the rheological properties of Pickering emulsions containing bentonite particles, CTAB, NaCl and soybean oil. Emulsification experiments were performed using mixing and homogenization at different speeds for 10 minutes. The effects of stirring speed and homogenization were investigated to determine the best conditions for producing a suitable Pickering emulsion for the intended application. In order to assess the influence of processing parameters on the Pickering emulsion rheological behavior average droplet size was measured and rheological tests were performed on all the emulsions samples. The rheological behavior of these emulsions is modeled by Casson's law. Results show that the stirring speed first decreases the average size of the droplets, and then an effect on the initial viscosity is observed. Increasing the stirring speed increases the values of the initial viscosity in contrast to the infinite viscosity which is influenced by the homogenization speed. On the other hand, these processing parameters significantly affect the values of the yield strength.
 Keywords: stirring speed, speed homogenization, rheological properties, Pickering emulsion.

Viscosity of Water-in-Oil Emulsions from Different American Petroleum Institute Gravity Brazilian Crude Oils

Water-in-oil (W/O) emulsions are very common in oil field operations and are formed as a result of energy input from turbulence caused by the flow in the production pipelines, pumps, and valves. Understanding emulsion rheological behavior is crucial to deal with flow assurance issues. This paper presents and discusses a series of rheological experiments carried out with synthetic emulsions formulated with 126 Brazilian crude oils with American Petroleum Institute (API) gravity ranging from 13° to 35°. This rheological study includes viscosity dependence upon the shear rate, temperature, and water volume fraction. The results show that crude oils with similar API gravity and viscosity can generate emulsions with very different viscosities (8–50 mPa s at 50 °C around 25° API gravity, for example) and different maximum water content limits. Besides, W/O emulsions that are prepared with either light (API gravity of >35°) or heavy (API gravity of <13°) crude oils are the emulsions observed to be the more diffi...

Experimental measurement and modeling of nanoparticle-stabilized emulsion rheological behavior

Emulsions have wide applications in various fields, especially in the petroleum industry. The rheological behavior of water-oil emulsions plays an important role in oil production, transportation and enhanced oil recovery methods Rheology of emulsions is affected by various factors such as dispersed phase fraction, droplet size distribution, a concentration of emulsifying agents, solid concentration, etc. Emulsion stabilization by solids, especially nanoparticles increased the stability, improved the rheological properties and consequently, incrementing the oil recovery from a subterranean formation. It can be pointed out that in very limited cases, the effects of nanoparticles on droplet size distribution of emulsion were investigated and models for prediction of the rheological behavior of solid-stabilized water-in-oil emulsions were not presented. The experiments were carried out using crude oil (petroleum) and fumed silica particle (namely Aerosil R972). In this communication, the effects of different parameters, including water volume fraction, nanoparticle concentration, shear rate, and angular frequency were investigated on the rheological behavior of water-in-oil emulsion. According to the results of rheological experiments, it can be pointed out that the influence of the nanoparticles on the viscosity of water-in-oil emulsions is mainly affected by the water/oil ratio, a number of nanoparticles, shear rate and angular frequency. Nanoparticle decreased water droplet diameter and increased the stability, elasticity and viscosity of the emulsion. In addition, for a better understanding of the effect of these parameters on the viscosity of the water-in-oil emulsions, apparent viscosity models were used. Based on the experimental data, a new equation was developed to estimate the relative viscosity of solid-free and solid-stabilized emulsions. The obtained results demonstrated that the proposed model has increased accuracy than previously published correlations.

Effects of ascorbic acid on the physiochemical, rheological, and antioxidant properties of citrus essential oil-based emulsion stabilized by pectin

ABSTRACTThe present study was conducted to enhance the peel of Citrus sinensis (sweet orange) by using their essential oils (EOs) as a potential source of natural bioactive molecules. EOs were obtained by hydrodistillation and their chemical profile was determined through GC-MS analysis. O/W EO emulsions were prepared using pectin as biopolymer emulsifier at different proportions, including different amounts of ascorbic acid (0, 0.5, and 1% w/w). The effect of pectin and ascorbic acid concentrations on the stability and rheological behavior of emulsions was investigated. It was found that adding ascorbic acid to the appropriate concentration of pectin enhances the interfacial membranes surrounding the oil droplets and decreases the droplet sizes. As a result both the viscoelastic modules and the resulting viscosity of emulsions increase leading to an improvement of their stability. Antioxidant activity of orange EO emulsion in combination with ascorbic acid was found significantly higher than that without ascorbic acid, and higher than that of individual components. Overall, this study would be helpful in developing more effectives systems with promising physical and antioxidant characteristics for the preservation of foods.

Rheological properties of inverse emulsions stabilized by ethanolamides of tall oil fatty acids

The paper presents the comparative analysis of inverse emulsion rheological behavior stabilized by monoethanolamide and diethanolamide of tall oil fatty acids, which are promising reagents for petroleum engineering. Flow curves of emulsions and volume ratio of dispersed phase have been obtained. The analysis of the dependence of Herschel–Bulkley model parameters on concentration of emulsifiers has been carried out. It is proved that emulsifiers affect weakly on the rheological parameters in high water phase content emulsions, while in cut-back emulsions their impact is registered to be stronger. It has been found that rheological parameters of the emulsions stabilized by monoethanolamide throughout the range of concentration are considerably higher than the samples on the base of diethanolamide. The experimental data proved the key impact of viscosity of dispersion medium on rheological behavior of cut-back emulsions.

Impact of Oil-in-Water Emulsion Composition and Preparation Method on Emulsion Physical Properties and Friction Behaviors

Emulsions have been used as a model food system for many studies on food behavior, including tribological studies. Several studies have examined the effect of fat content and emulsifier on emulsion friction behavior; however, other emulsion parameters such as ionic strength, pH, and homogenization pressure have received little attention in the literature. Additionally, emulsion friction measurements are generally compared to sensory data rather than physical property data. Thus, the objective of this study was to investigate the effect of various emulsion parameters on emulsion physical properties and rheological and friction behavior. Emulsion salt content, pH, and homogenization pressure all affected friction behavior, with specific effects dependent on the emulsifying protein. All emulsions showed reduced friction coefficient with increased fat content. Emulsion rheological behavior was not strongly impacted by changes in the emulsion parameters. Changing emulsion pH had the strongest effect on emulsion physical properties. The results of this study suggest that tribology may be used to develop a “fingerprint” for emulsions prepared using different parameters, allowing improved differentiation of these emulsions compared to traditional rheometry.

Development, characterization and antioxidant activity of polysorbate based O/W emulsion containing polyphenols derived from Hippophae rhamnoides and Cassia fistula

The objective of this study was to develop a pharmaceutical O/W emulsion containing plant-derived polyphenol extracts and evaluate its stability and antioxidant activity. O/W emulsions were prepared using ionic surfactant polysorbate 80 (Tween 80®). The odorwas adjusted with few drops of blue sea fragrance. DPPH (1,1-diphenyl-2-picrylhydrazyl) assay was used to evaluate the antioxidant activity of the plant extracts alone and emulsions containing these extracts. Physical stability was assessed by submitting the emulsions to storage at 8 ºC, 25 ºC, 40 ºC and 40 ºC + 70% RH (relative humidity) for two months. Various physical characteristics of emulsions monitored, include color, creaming, liquefaction, centrifugation and pH. Brookfield rotational rheometer was used to determined viscosities and rheological behavior of emulsions. Different types of emulsion were determined microscopically, while pH values of emulsions were measured by a pH meter. Electrical conductivity data confirmed that the outer phase was water. Samples presented an acceptable pH value for an external topical use. Shear thinning behaviour was observed for all emulsions. The polyphenol-rich-plant-derived extracts alone and the extract containing emulsions showed good antioxidant activities. This research confirmed that the method used was suitable for preparing emulsions with Hippophae rhamnoids and Cassia fistula extracts, suggesting that those emulsions are suitable for topical use.

The role of emulsifier in stabilization of emulsions containing colloidal alumina particles

This paper focuses on the study on rheological behaviour of emulsions, stabilized by both differently modified dispersible colloidal Boehmite alumina nanoparticles and a non-ionic emulsifier. Hysteresis loop measurements and dynamic rheological measurements were carried out in linear and non-linear regimes on two different emulsion systems – water-in-oil (W/O) and oil-in-water (O/W) emulsions.Emulsion stabilized by a combination of moderately hydrophobic particles and a non-ionic emulsifier is an O/W emulsion. The addition of emulsifier improved the stability, however, did not show a significant influence on the emulsion flow behaviour. The emulsion, stabilized by both – nanoparticles and emulsifier – showed a complicated behaviour, i.e. sometimes it exhibited thixotropy or antithixotropy and sometimes both of them.Emulsion stabilized by rather hydrophobic particles and a non-polar emulsifier is a W/O emulsion. The emulsion is very homogenous and exhibited very weak thixotropy. Dynamic measurements showed that G’ was almost equal to G” and both parameters were frequency-dependent, indicating a viscous liquid-like system with little network structure if any. With addition of emulsifier, the rather elastic solid-like emulsion structure may be changed into the viscous liquid-like structure.In order to get a better understanding of relationships between rheological behaviour and microstructure, differential scanning calorimetry (DSC) results and optical microscopic images of the emulsions studied were discussed.

Rheological properties of emulsions stabilized by green banana (Musa cavendishii) pulp fitted by power law model

In this work, the rheological behaviour of emulsions (mayonnaises) stabilized by green banana pulp using the response surface methodology was studied. In addition, the emulsions stability was investigated. Five formulations were developed, according to design for constrained surfaces and mixtures, with the proportion, respectively: water/soy oil/green banana pulp: F1 (0.10/0.20/0.70), F2 (0.20/0.20/0.60), F3 (0.10/0.25/0.65), F4 (0.20/0.25/0.55) and F5 (0.15/0.225/0.625) .Emulsions rheological properties were performed with a rotational Haake Rheostress 600 rheometer and a cone and plate geometry sensor (60-mm diameter, 2º cone angle), using a gap distance of 1mm. The emulsions showed pseudoplastic behaviour and were adequately described by the Power Law model. The rheological responses were influenced by the difference in green banana pulp proportions and also by the temperatures (10 and 25ºC). The formulations with high pulp content (F1 and F3) presented higher shear stress and apparent viscosity. Response surface methodology, described by the quadratic model,showed that the consistency coefficient (K) increased with the interaction between green banana pulp and soy oil concentration and the water fraction contributed to the flow behaviour index increase for all emulsions samples. Analysis of variance showed that the second-order model had not significant lack-of-fit and a significant F-value, indicating that quadratic model fitted well into the experimental data. The emulsions that presented better stability were the formulations F4 (0.20/0.25/0.55) and F5 (0.15/0.225/0.625).

Rheological Behavior of Food Emulsions Mixed with Saliva: Effect of Oil Content, Salivary Protein Content, and Saliva Type

In this paper, we studied the effect of saliva on the rheological properties of β-lactoglobulin- and lysozyme-stabilized emulsions, prepared at pH = 6.7 in relation to variation of emulsions- and saliva-related parameters. The effect of oil–volume fraction (2.5% w/w to 10% w/w), salivary protein concentration (0.1 to 0.8 mg ml−1), and the use of both stimulated and unstimulated saliva was investigated. Viscosity and storage modulus were measured before (ηemul and G′emul, respectively) and after addition of saliva (ηmix and G′mix). To better estimate the changes due to saliva-induced flocculation of the emulsions, the ratios ηmix/ηemul, G′mix/G′emul were calculated. In addition, tan δ (=the ratio of the loss and storage moduli) was investigated to evaluate the viscoelastic behavior of the emulsion/saliva mixtures. Increasing the oil–volume fraction and salivary protein concentration resulted in an increase in ηmix/ηemul and G′mix/G′emul, while a decrease in tan δ of the emulsion/saliva mixtures is occurring. When compared with unstimulated saliva, mixing β-lactoglobulin-stabilized emulsions with stimulated saliva led to a reduction in ηmix/ηemul and G′mix/G′emul, and an augment of tan δ at all measured deformations. In case of lysozyme-stabilized emulsions, the use of stimulated saliva increased G′mix/G′emul for γ < 3 when compared to unstimulated saliva. The effect of stimulated saliva on the ηmix/ηemul and tan δ in this mixture is similar to that of unstimulated saliva. These results indicate that the influence of stimulated saliva on the rheological parameters of emulsion/saliva mixtures largely depends on the type of emulsions. To conclude, our findings demonstrate that the rheological behavior of emulsions upon mixing with saliva is greatly affected by both saliva and emulsion properties.

Rheological properties of corn oil emulsions stabilized by commercial micellar casein and high pressure homogenization

The rheological behavior of corn oil emulsions prepared by high pressure homogenization (HPH) was investigated. Coarse emulsions of corn oil (10–30 g oil/100 g emulsion) in casein dispersions containing 0.5–3.5 g micellar casein/100 g casein dispersion in an oil-free basis were homogenized at 0–300 MPa. Flow behavior under continuous increasing (0–150 s −1) or decreasing (150–0 s −1) shear rate was tested. Emulsions that showed macroscopic change in consistency were tested for viscoelasticity ( G′). Homogenization of emulsions with low oil concentration (10 g/100 g) resulted in Newtonian behavior for all treatment pressures. The rheological behavior of emulsions with higher oil concentration (30 g/100 g) was dependent on casein concentration in the aqueous phase and varied from Newtonian to shear thinning. Homogenization pressures between 20 and 100 MPa induced the formation of a gel-like structure possibly through pressure-induced interactions between caseins surrounding adjacent droplets.