Dispersed Phase Mass Fraction Research Articles

Insights of the ability of gelatinized fractions from non-chemical modified corn, rice, wheat, and waxy corn starches to stabilize O/W emulsions

Non-chemical modified native corn (NCS), rice (NRS), wheat (NWS), and waxy corn (WCS) starch dispersions (5.0 g/100 g water) were heated (90 °C, 20 min) for producing gelatinized starch dispersions (GSD). GSD were centrifuged and the supernatant starch fraction (SF) was used for preparation of O/W emulsions (dispersed phase mass fraction of 0.15). The interfacial activity of the different SFs was assessed by dynamic interfacial tension measurements. The SF from NCS, NRS and NWS showed significantly higher and faster interfacial tension decaying rates than the WCS SF. All the SFs were able to form O/W emulsions. The volume-weighted mean droplet diameter (d4,3) of the fresh emulsions were significantly different ranging from ∼1.4 to 19 μm. The emulsions made with SFs from NCS, NRS and NWS showed larger d4,3 and faster creaming rates than that made with SF of WCS. The latter produced an emulsion with practically unchanged d4,3 and slowest creaming rate with storage time. FTIR, XRD, zeta-potential measurements, and adsorption time relaxation constants allowed postulating that emulsion stability was related to the formation of inclusion starch-lipid complexes at the oil-water interface. This study provides insights about the phenomena occurring on O/W emulsions interface due to interactions between cooked starch fractions from different botanical origin and lipids, and which might occur during food processing.

Rheological behavior of high internal phase water-in-oil emulsions: Effects of droplet size, phase mass fractions, salt concentration and aging

The rheological properties of high internal phase emulsions (HIPEs), comprising polydisperse aqueous droplets in oil, have been characterized as a function of emulsification time, salt concentration, phase mass fractions and aging. The droplet size distribution and structural details of the emulsion samples were obtained using cryogenic-scanning electron microscopy (cryo-SEM) and optical microscopy. For rheological characterisation, amplitude sweep tests performed on HIPE samples with a high mass fraction of dispersed phase (93.5wt%) show that the strain behavior, especially the yield strain (εy) and crossover strain (εc), are almost independent of the droplet size and polydispersity. However, emulsions with smaller droplets have higher yield stress (τy) and storage moduli (G′) values; explanations for these observations, based on the physical properties of the systems are suggested. Furthermore, it is observed that, for constant mass fractions of oil and aqueous phases, the strain behavior is also independent of the salt concentration in the dispersed phase. Our findings indicate that, independently of the salt concentration, the energy requirement for the emulsion to start flowing is greater when smaller droplets are present. Aging studies, performed over a period of 6months, show no significant change in the rheological properties of the HIPEs. Experimental rheology data is compared to the Princen and Kiss model, and with modified Mougel model (Ind. Eng. Chem. Res. 2011, 50, 10359–10365), giving insight into the critical effects of non-ideality induced by polydispersity in thickened emulsions.

Formation of Concentrated Nanoemulsion by W/O Microemulsion Dilution Method: Biodiesel, Tween 80, and Water System

In this work, we show the formation of concentrated green O/W nanoemulsion (dispersed phase mass fraction was up to 0.5) by diluting W/O microemulsion in the water/Tween 80/biodiesel system. The mechanism of the formation of nanoemulsions was examined and illustrated by small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM). At high temperature, nanosized droplets formed spontaneously due to the surfactant migration and inversion upon dilution of W/O microemulsions, but these droplets were highly unstable. When cooled to room temperature, their stability was highly enhanced due to the decrease of collision frequency rate and the enhancement of stabilization of the oil/water interface. Even though, the Ostwald ripening still results in growth of droplets of the nanoemulsions after long-term storage, which limits the practical applications of nanoemulsions. W/O microemulsions are thermodynamic systems. Hence, W/O microemulsions that can form nanoemulsions by simple dil...

Formulation and optimization by experimental design of eco-friendly emulsions based on d-limonene

d-Limonene is a natural occurring solvent that can replace more pollutant chemicals in agrochemical formulations.In the present work, a comprehensive study of the influence of dispersed phase mass fraction, ϕ, and of the surfactant/oil ratio, R, on the emulsion stability and droplet size distribution of d-limonene-in-water emulsions stabilized by a non-ionic triblock copolymer surfactant has been carried out.An experimental full factorial design 32 was conducted in order to optimize the emulsion formulation. The independent variables, ϕ and R were studied in the range 10–50wt% and 0.02–0.1, respectively. The emulsions studied were mainly destabilized by both creaming and Ostwald ripening. Therefore, initial droplet size and an overall destabilization parameter, the so-called turbiscan stability index, were used as dependent variables. The optimal formulation, comprising minimum droplet size and maximum stability was achieved at ϕ=50wt%; R=0.062.Furthermore, the surface response methodology allowed us to obtain the formulation yielding sub-micron emulsions by using a single step rotor/stator homogenizer process instead of most commonly used two-step emulsification methods. In addition, the optimal formulation was further improved against Ostwald ripening by adding silicone oil to the dispersed phase.The combination of these experimental findings allowed us to gain a deeper insight into the stability of these emulsions, which can be applied to the rational development of new formulations with potential application in agrochemical formulations.

Pressure correction staggered schemes for barotropic one-phase and two-phase flows

We assess in this paper the capability of a pressure correction scheme to compute shock solutions of the homogeneous model for barotropic two-phase flows. This scheme is designed to inherit the stability properties of the continuous problem: the unknowns (in particular the density and the dispersed phase mass fraction y) are kept within their physical bounds, and the entropy of the system is conserved, thus providing an unconditional stability property. In addition, the scheme keeps the velocity and pressure constant through contact discontinuities. These properties are obtained by coupling the mass balance and the transport equation for y in an original pressure correction step. The space discretization is staggered; the numerical schemes which are considered are the Marker-And Cell (MAC) finite volume scheme and the nonconforming low-order Rannacher–Turek and Crouzeix–Raviart finite element approximation. In either case, a finite volume technique is used for all convection terms. Numerical experiments performed here show that, provided that a sufficient dissipation is introduced in the scheme, it converges to the (weak) solution of the continuous hyperbolic system. Observed orders of convergence for 1D Riemann problems as a function of the mesh and time step at constant CFL number vary with the studied case, and the CFL number and on the regularity of the solution. They range from 0.5 to greater than 1 for the velocity and the pressure; in most cases, the density and mass fraction converge with a 0.5 order. Finally, the scheme shows a satisfactory behaviour up to large CFL numbers.

Rheological properties of a double emulsion nutraceutical system incorporating chia essential oil and ascorbic acid stabilized by carbohydrate polymer–protein blends

Abstract Four water-in-oil-in water (W1/O/W2) double emulsions were made by adding the primary emulsion (W1/O) containing 74% (w/w) of chia essential oil, 6% (w/w) of ascorbic acid, and a 0.2 dispersed phase mass fraction ( φ W 1 / O ) to aqueous solutions (W2) of mesquite gum (MG), maltodextrin DE-10 (MD) and whey protein concentrate (WPC) in different proportions (MG66–MD17–WPC17 and MG17–MD66–WPC17), and in a ratio of 1:2.12 and 1:4.12 W1/O to dry biopolymers blends solids. All the double emulsions showed type C morphologies and only slight changes in the volume-weighted mean diameter (d4,3) throughout the storage time, indicative of good stability, despite they presented bimodal size distributions, but the double emulsion formulated with a predominant proportion of MD and ratio 1:2.12 provided a higher stability against droplet coalescence. All the double emulsions displayed viscoelastic character dependent on frequency.

Influence of CaCl 2 on the water vapor permeability and the surface morphology of mesquite gum based edible films

Oil-in-water (O/W) emulsions with a dispersed phase mass fraction (φ m ) of 0.175 were prepared by dispersing a blend of candelilla wax/mineral oil (2:1 ratio) in 10 g of mesquite gum per 100 g of water containing either CaCl 2 (0.0, 0.1, 0.2, 0.3, 0.4 or 0.5 g) alone or combined with 1.5 g of glycerol. The mean volumetric droplet size ( d 3,0), the rate of droplet coalescence (C) and the viscosity-shear rate behavior of the emulsions were affected by the addition of CaCl 2 alone or combined with glycerol. The Carreau–Yasuda model fitted best the viscosity-shear rate data of all the emulsions. The surface morphology of the edible films, analyzed by Atomic Force Microscopy (AFM), exhibited a strong dependence on the CaCl 2 concentration. Maximum roughness occurred with a CaCl 2 concentration of 0.3 g per 100 g. Films with glycerol showed significantly higher roughness than those with only CaCl 2. Water vapor permeability (WVP) was significantly lowered as the concentration of CaCl 2 increased from 0.1 to 0.3 g per 100 g in the coatings, but increased again at CaCl 2 concentrations of 0.4–0.5 g per 100 g. Coatings containing glycerol displayed significant higher WVP.

Ferrous bisglycinate content and release in W 1/O/W 2 multiple emulsions stabilized by protein–polysaccharide complexes

ABSTRACT Ferrous bisglycinate aqueous solution was entrapped in the inner phase (W1) of water-in-oil-in-water (W1/O/W2) multiple emulsions. The primary ferrous bisglycinate aqueous solution-in-mineral oil (W1/O) emulsion contained 15% (w/w) ferrous bisglycinate, had a dispersed phase mass fraction of 0.5, and was stabilized with a mixture of Grindsted PGPR 90:Panodan SDK (6:4 ratio) with a total emulsifiers concentration of 5% (w/w). This primary emulsion was re-emulsified in order to prepare W1/O/W2 multiple emulsions, with a dispersed mass fraction of 0.2, and stabilized using protein (whey protein concentrate (WPC)):polysaccharide (gum arabic (GA) or mesquite gum (MG) or low methoxyl pectin (LMP)) complexes (2:1 ratio) in the W2 aqueous phase. The W1/O/W2 multiple emulsion stabilized with WPC:MG (5% w/w total biopolymers concentration) provided smaller droplet sizes (2.05 μm), lower rate of droplet coalescence (7.09 × 10−7 s−1), better protection against ferrous bisglycinate oxidation (29.75% Fe3+) and slower rate of ferrous bisglycinate release from W1 to W2 (KH = 0.69 mg mL−1 min−0.5 in the first 24 h and 0.07 mg mL−1 min−0.5 for the next 19 days of storage time). Better encapsulation efficiencies, enhanced protection against oxidation and slower release rates of ferrous bisglycinate were achieved as the molecular weight of the polysaccharide making up protein:polysaccharide complex was higher. Thus, the factor that probably affected most the overall functionality of multiple emulsions was the thickness of the complex adsorbed around the multiple emulsion oil droplets. These thicknesses determined indirectly by measuring the z-average diameter of the complexes, and that of the WPC:MG (529.4 nm) was the largest.

Influence of the fragmentation of multiple globules on the rheological properties of W/O/W multiple emulsions

The purpose of our work was to study the behavior of W/O/W multiple emulsions submitted to a shear flow by applying the theoretical framework developed by Taylor to describe the deformation and the bursting of simple oily globules under shear. The formulation parameters taken into consideration were the mass fraction of dispersed phase and the viscosity of the continuous phase. The conductometric analysis carried out to study the release under shear of the electrolyte entrapped inside the internal aqueous phase of the multiple emulsions, together with microscopic and granulometric analyses, showed that Taylor’s framework could be applied to multiple emulsions. Rheological analyses were also carried out and confirmed the bursting of the globules in parallel with the granulometric studies. This phenomenon could be visualized by rheograms showing a more or less large hysteresis loop. The mechanisms which occur during the bursting are complex and depend on the shear time.