Effect of Conformation of Sugar Beet Pectin on the Interfacial and Emulsifying Properties

The influence of the conformation of sugar beet pectin (SBP) on the interfacial and emulsifying properties was investigated. The colloidal properties of SBP, such as zeta potential and hydrodynamic diameter, were characterized at different pH levels. Furthermore, pendant drop tensiometry and quartz crystal microgravimetry were used to study adsorption behavior (adsorbed mass and adsorption rate) and stabilizing mechanism (layer thickness and interfacial tension). A more compact conformation resulted in a faster reduction of interfacial tension, higher adsorbed mass, and a thicker adsorption layer. In addition, emulsions were prepared at varying conditions (pH 3–5) and formulations (1–30 wt% MCT oil, 0.1–2 wt% SBP), and their droplet size distributions were measured. The smallest oil droplets could be stabilized at pH 3. However, significantly more pectin was required at pH 3 compared to pH 4 or 5 to sufficiently stabilize the oil droplets. Both phenomena were attributed to the more compact conformation of SBP at pH < pKa: On the one hand, pectins adsorbed faster and in greater quantity, forming a thicker interfacial layer. On the other hand, they covered less interfacial area per SBP molecule. Therefore, the SBP concentration must be chosen appropriately depending on the conformation.

An Analysis of Two Fluid Layers Enclosed Between Two Non-Porous Surfaces

The stability of a two-phase interface is a crucial occurrence that involves the design of many engineering applications. It correlates the spatial and droplet size-distributions of many fluid spraying applications and has a great effect on the estimations of the critical heat flux of systems that involves phase change or evaporation. However, the existing hydrodynamic models are only able to predict the stability of a plane fluid sheet, surrounded by an infinite pool of liquid. The case of a thin sheet of liquid surrounding a vapor sheet and enclosed between two walls has not been studied yet. The present paper solves this problem using a linearized stability analysis. Velocity potentials satisfying these conditions are introduced and a complete analysis is presented.

Comparative Study of Physicochemical Properties of Nanoemulsions Fabricated with Natural and Synthetic Surfactants

This work aims to evaluate the effect of two natural (whey protein isolate, WPI, and soy lecithin) and a synthetic (Tween 20) emulsifier on physicochemical properties and physical stability of food grade nanoemulsions. Emulsions stabilized by these three surfactants and different sunflower oil contents (30% and 50% w/w), as the dispersed phase, were fabricated at two levels of homogenization pressure (500 and 1000 bar). Nanoemulsions were characterized for droplet size distribution, Zeta-potential, rheological properties, and physical stability. Dynamic light scattering showed that droplet size distributions and D50 values were strongly affected by the surfactant used and the oil content. WPI gave similar droplet diameters to Tween 20 and soy lecithin gave the larger diameters. The rheology of emulsions presented a Newtonian behavior, except for WPI-stabilized emulsions at 50% of oil, presenting a shear-thinning behavior. The physical stability of the emulsions depended on the surfactant used, with increasing order of stability as follows: soy lecithin < Tween 20 < WPI. From our results, we conclude that WPI is an effective natural replacement of synthetic surfactant (Tween 20) for the fabrication of food-grade nanoemulsions.

Combining cellulose nanofibrils and galactoglucomannans for enhanced stabilization of future food emulsions

The use of wood-derived cellulose nanofibrils (CNFs) or galactoglucomannans (GGM) for emulsion stabilization may be a way to obtain new environmentally friendly emulsifiers. Both have previously been shown to act as emulsifiers, offering physical, and in the case of GGM, oxidative stability to the emulsions. Oil-in-water emulsions were prepared using highly charged (1352 ± 5 µmol/g) CNFs prepared by TEMPO-mediated oxidation, or a coarser commercial CNF, less charged (≈ 70 µmol/g) quality (Exilva forte), and the physical emulsion stability was evaluated by use of droplet size distributions, micrographs and visual appearance. The highly charged, finely fibrillated CNFs stabilized the emulsions more effectively than the coarser, lower charged CNFs, probably due to higher electrostatic repulsions between the fibrils, and a higher surface coverage of the oil droplets due to thinner fibrils. At a constant CNF/oil ratio, the lowest CNF and oil concentration of 0.01 wt % CNFs and 5 wt % oil gave the most stable emulsion, with good stability toward coalescence, but not towards creaming. GGM (0.5 or 1.0 wt %) stabilized emulsions (5 wt % oil) showed no creaming behavior, but a clear bimodal distribution with some destabilization over the storage time of 1 month. Combinations of CNFs and GGM for stabilization of emulsions with 5 wt % oil, provided good stability towards creaming and a slower emulsion destabilization than for GGM alone. GGM could also improve the stability towards oxidation by delaying the initiation of lipid oxidation. Use of CNFs and combinations of GGM and CNFs can thus be away to obtain stable emulsions, such as mayonnaise and beverage emulsions.

Impact of entrainment-mixing and turbulent fluctuations on droplet size distributions in a cumulus cloud: An investigation using Lagrangian microphysics with a sub-grid-scale model

Entrainment-mixing and turbulent fluctuations critically impact cloud droplet size distributions (DSDs) in cumulus clouds. This problem is investigated via a new sophisticated modeling framework using the CM1 LES model and a Lagrangian cloud microphysics scheme – the “super-droplet method” (SDM) – coupled with sub-grid-scale (SGS) schemes for particle transport and supersaturation fluctuations. This modeling framework is used to simulate a cumulus congestus cloud. Average DSDs in different cloud regions show broadening from entrainment and secondary cloud droplet activation (activation above the cloud base). DSD width increases with increasing entrainment-induced dilution as expected from past work, except in the most diluted cloud regions. The new modeling framework with SGS transport and supersaturation fluctuations allows a more sophisticated treatment of secondary activation compared to previous studies. In these simulations, it contributes about 25%of the cloud droplet population and impacts DSDs in two contrastingways: narrowing in extremely diluted regions and broadening in relatively less diluted. SGS supersaturation fluctuations contribute significantly to an increase in DSD width via condensation growth and evaporation. Mixing of super-droplets from SGS velocity fluctuations also broadens DSDs. The relative dispersion (ratio of DSD dispersion and mean radius) negatively correlates with grid-scale vertical velocity in updrafts, but is positively correlated in downdrafts. The latter is from droplet activation driven by positive SGS supersaturation fluctuations in grid-mean subsaturated conditions. Finally, the sensitivity to model grid length is evaluated. The SGS schemes have greater influence as the grid length is increased, and they partially compensate for the reduced model resolution.

Synthesis and Use of Janus SiO2 Nanoparticles for Formulating Model Heavy Oil Macroemulsions

<p>Janus nanoparticles have applications in many fields. Particularly, the oil industry is interested in applying them for enhanced oil recovery. Within this context, there is a need to understand the influence of the factors involved in the formulation of crude oil type emulsions over their properties and rheological behavior. In this contribution, spherical SiO₂ Janus nanoparticles of two different sizes were synthesized and used as surfactants for the formulation of aqueous emulsions with two model oils: namely, squalane and vacuum gas oil. Factorial experiments were designed and made to analyze the effects of the particle size of the Janus nanoparticles, the water content, the emulsification energy, and of the second and third order interactions between these variables over the droplet size distributions, polydispersity, and rheological profiles of the emulsions. On the one hand, it was found that the used Janus nanoparticles produced either water in oil (for vacuum gas oil) or oil in water (for squalane) depending on the chemistry of the oil phase. On the other hand, it was demonstrated that non-additive factors play an important role over the properties of the emulsions; especially in the case of the water in oil ones. These effects also implied non-additive correlations between the droplet size distributions of the emulsions and their rheological behavior. Therefore, this work demonstrates that simpler linear relationships do not suffice for finding the best conditions for formulating crude oil type emulsions aimed for applications such as enhanced oil recovery.</p>

Synthesis and Use of Janus SiO2 Nanoparticles for Formulating Model Heavy Oil Macroemulsions

<p>Janus nanoparticles have applications in many fields. Particularly, the oil industry is interested in applying them for enhanced oil recovery. Within this context, there is a need to understand the influence of the factors involved in the formulation of crude oil type emulsions over their properties and rheological behavior. In this contribution, spherical SiO₂ Janus nanoparticles of two different sizes were synthesized and used as surfactants for the formulation of aqueous emulsions with two model oils: namely, squalane and vacuum gas oil. Factorial experiments were designed and made to analyze the effects of the particle size of the Janus nanoparticles, the water content, the emulsification energy, and of the second and third order interactions between these variables over the droplet size distributions, polydispersity, and rheological profiles of the emulsions. On the one hand, it was found that the used Janus nanoparticles produced either water in oil (for vacuum gas oil) or oil in water (for squalane) depending on the chemistry of the oil phase. On the other hand, it was demonstrated that non-additive factors play an important role over the properties of the emulsions; especially in the case of the water in oil ones. These effects also implied non-additive correlations between the droplet size distributions of the emulsions and their rheological behavior. Therefore, this work demonstrates that simpler linear relationships do not suffice for finding the best conditions for formulating crude oil type emulsions aimed for applications such as enhanced oil recovery.</p>