On the key role of process parameters to control stability and properties of Pickering emulsions stabilized by montmorillonite

Pea protein [Pisum sativum] as stabilizer for oil/water emulsions

A map of stability for various water/oil/pea protein compositions has been plotted from the numerous reported results. Two clear regions of stability were identified. High internal oil phase emulsions with 70-80%, v/v oil content stabilized by total pea protein concentration <2.5%, w/v showed stability. Low oil content of 10-30%, v/v for a range of total pea protein concentrations >0.5%, w/v have also been identified as stable. Intermediate oil content and pea protein concentrations >4% w/v are unexplored regions and are likely to be areas of fruitful future research. The wide range of stability suggests that different stabilization mechanisms could be important for different compositions and careful consideration has to be taken to avoid oversimplification. Both stabilization with particles, i.e. Pickering emulsions, and protein unfolding have been suggested as mechanisms. The diverse way of describing stability makes it difficult to intercompare results in different studies. A summary of different oil types used have been presented and several properties such as dynamic viscosity, density, the dielectric constant and interfacial tension have been summarized for common vegetable oils. The type of vegetable oil and emulsion preparation techniques were seen to have rather little effect on emulsion stability. However, the different extraction methods and processing of the pea material had more effect, which could be attributed to changing composition of different proteins and to the states of aggregation and denaturing. Careful consideration has to be taken in the choice of extraction method and an increased understanding of what contributes to the stability is desirable for further progress in research and eventual product formulation.

Quantitative effects of formulation and process parameters on the structure of food emulsions stabilized with an unrefined by-product powder: A statistical approach

Apple pomace powder is a sustainable food ingredient, but its more complex composition compared to commonly purified ingredients could curb its valorization. This study assesses how physicochemical properties, formulation and process factors influence the physical properties of the emulsion. The two main objectives were to: 1) unravel the structuring and stabilizing mechanisms of such complex systems and 2) account for interactions between various parameters instead of studying them separately. Thirty-one experimental samples were formulated to produce a variety of microstructures with droplet diameters ranging from 28 to 105 µm, textures with viscosity ranging from 135 to 2,490 mPa.s at 50 s-1 and stabilities. Using multicriteria selection of effects revealed that the concentration of the powder and the size of solid particles are the main levers for tailoring the structure-function relationships of the emulsions. Solid particles play a key role in both structuring and stabilizing the emulsions. Process parameters have an impact on the emulsification step by modifying the adsorption rate of solid particles. In conclusion, modelling advanced our understanding of stabilizing mechanisms of the emulsions produced by apple pomace and will enable efficient knowledge transfer for industrial applications.

Ionically crosslinked cellulose nanocrystals by metal nitrates for the preparation of stable emulsions with tunable interface properties

Biologically extracted cellulose nanocrystals (CNCs) are rod-like and amphiphilic materials with surface-exposed (hydrophilic sites) and hidden (hydrophobic sites) hydroxyl groups. These physicochemical characteristics make CNCs suitable for use as emulsifying agents to stabilize emulsions. Stable oil-in-water emulsions, using sulfated (i.e., -[Formula: see text]) CNCs that were ionically crosslinked with alkaline-earth (i.e., [Formula: see text]) or transition-d-block (i.e., [Formula: see text]) metal cations, were developed without the use of any synthetic surfactants or prior functionalization of pure CNCs with hydrophobic molecules. Various emulsion surface properties such as interfacial tension, surface charge, surface chemistry, as well as rheology were characterized. Ionically crosslinked CNCs (iCNCs) adsorbed at the interface of an oil and water and fortified the emulsion droplets (5-30 µm) against coalescence by lowering the interfacial tension from 65 mN/m (i.e., pure CNC mixture with oil) to 25 mN/m (i.e., iCNC mixture with oil) and reducing zeta potential with surface charge values (-30 mV to -10 mV), ideal to maintain droplet layer assembly at the water-oil interface. This study provided an alternative approach to achieve particle-stabilized and surfactant-free emulsions by using divalent metal nitrates to develop "clean" emulsion-based technologies for applications in many industries from agriculture to food to pharmaceuticals.

Pickering emulsions synergistically stabilized by sugar beet pectin and montmorillonite exhibit enhanced storage stability and viscoelasticity

Sugar beet pectin (SBP) is a naturally occurring emulsifying type of pectin fabricated into nanocomposites with montmorillonite (MMT) and then introduced as a stabilizer for high internal phase emulsions (HIPEs). SBP-MMT composites performed well in emulsifying medium-chain triglyceride with an oil volume fraction (φ) of 0.1-0.85 and SBP/MMT mass ratios of 1:0.1-1:0.75. The two representative high internal phase emulsions stabilized by SBP-MMT composites at different SBP/MMT mass ratios exhibited good stability against creaming and coalescence. In these emulsion systems, SBP and MMT formed a network in the continuous phase that markedly improved the rheological properties, including the storage modulus (by 3 orders of magnitude). Confocal light scattering microscopy analysis indicated that a fraction of MMT could work synergistically with SBP in adsorbing on oil droplet surfaces, enhancing stability. SBP-MMT composites stabilized high internal phase emulsions destabilized after the freeze-thaw treatment (-40 °C for 20 h and 25 °C for 4 h) but could be facilely re-emulsified via high-speed shearing. The gastrointestinal digestion behaviors were also modified by stabilizing SBP and MMT. Overall, this work reveals a hitherto undocumented strategy for fabricating highly stable emulsions based on SBP-MMT composites which have huge prospects for application in the food and related industries.

Application of Population Balance Models in Particle-Stabilized Dispersions

In this study, a first approach to model drop size distributions in agitated nanoparticle-stabilized liquid/liquid systems with population balance equations is presented. Established coalescence efficiency models fail to predict the effect of steric hindrance of nanoparticles at the liquid/liquid interface during the film drainage process. A novel modified coalescence efficiency is developed for the population balance framework based on the film drainage model. The elaborate submodel considers the desorption energy required to detach a particle from the interface, representing an energy barrier against coalescence. With an additional implemented function in the population balance framework, the interface coverage rate by particles is calculated for each time step. The transient change of the coverage degree of the phase interface by particles is thereby considered in the submodel. Validation of the modified submodel was performed with experimental data of agitated water-in-oil (w/o) dispersions, stabilized by well-defined spherical silica nanoparticles. The nanospheres with a size of 28 nm are positively charged and were hydrophobized by silanization with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammoniumchloride. This modeling approach is a first step toward predicting time-resolved dynamic drop size distributions of nanoparticle-stabilized liquid/liquid systems.

Clays as Vehicles for Drug Photostability

Clay minerals are often used due to their high adsorption capacity, which has sparked interest in their biological applications to stabilize drugs and pharmaceutical products. This research aims to summarize information about the stability of drugs, cosmetics, dermocosmetics, and pharmaceutical compounds incorporated in the structure of different clay minerals. The databases used to search the articles were Web of Science, Scopus, PubMed, and Science Direct. Photostabilization of these compounds is reviewed and its importance demonstrated. For biological applications, the increase in solubility and bioavailability of clay minerals has proven useful for them as drug carriers. While their natural abundance, low toxicity, and accessible cost have contributed to classical applications of clay minerals, a wide range of interesting new applications may be facilitated, mainly through incorporating different organic molecules. The search for new functional materials is promising to challenge research on clay minerals in biological or biotechnological approaches.

Fabrication of hydrophobic NiFe2O4@poly(DVB-LMA) sponge via a Pickering emulsion template method for oil/water separation

Super-hydrophobic porous absorbents are convenient, low-cost, efficient and environment-friendly materials in the treatment of oil spills. In this work, a simple Pickering emulsion template method was employed to fabricate an interconnected porous poly(DVB-LMA) sponge. A new co-Pickering stabilization system of Span 80 and NiFe2O4 nanoparticles was used to prepare ultra-concentrated internal phase water-in-oil (W/O) emulsions. After further polymerization, the resulting sponges were generated, which exhibited excellent adsorption selectivity due to the super-hydrophobicity and super-lipophilicity. Furthermore, the characterization results indicated that the composites had superior thermal stability, low density, high porosity and a flexible three-dimensional porous structure. Besides, the addition of nickel ferrite nanoparticles provided the materials with extra magnetic operability. High oil adsorption capacity (up to 36.9-84.2 g g-1), high oil retention, fast adsorption rate and superior reusability allowed the materials to be applied in the treatment of oily water.