Particle-stabilized Emulsions Research Articles

Ultrasound Control of Pickering Emulsion-Based Capsule Preparation.

Capsules with microparticle shells became of great interest due to their potential in many fields. Those capsules can be fabricated at high temperatures from particle-stabilized emulsions (Pickering emulsions) by sintering together particles that cover droplets. One of the problems with such an approach is accurately controlling whether particles are already sintered and creating the rigid capsule shell of a capsule. Here, we propose using a non-destructive ultrasound method for monitoring Pickering emulsion-based capsules prepared using heating under an alternating magnetic field. The polyethylene microparticles that were responsive to temperatures higher than 112 °C were used as droplet stabilizers together with iron oxide nanoparticles. During the coalescence of the droplets, facilitated by an external electric field, the ultrasonic attenuation increased, giving evidence that the ultrasound method detects structural changes in Pickering emulsions. The main change was the difference in the droplets' size, which was also observed via optical microscopy. The attenuation of ultrasound increased even more when measured after magnetic heating for the same concentration of particle stabilizers. Simultaneously, the values of ultrasonic velocity did not exhibit similar variety. The results show that the values of the attenuation coefficient can be used for a quantitative evaluation of the capsule formation process.

Spatiotemporal coordination of antigen presentation and co-stimulatory signal for enhanced anti-tumor vaccination

Controlled-release systems enhance anti-tumor effects by leveraging local antigen persistence for antigen-presenting cells (APCs) recruitment and T cell engagement. However, constant antigen presentation alone tends to induce dysfunction in tumor-specific CD8+ T cells, neglecting the synergistic effects of co-stimulatory signal. To address this, we developed a soft particle-stabilized emulsion (SPE) to deliver lipopeptides with controlled release profiles by adjusting their hydrophobic chain lengths: C6-SPE (fast release), C10-SPE (medium release), and C16-SPE (slow release). Following administration, C6-SPE release antigen rapidly, inducing early antigen presentation, whereas C16-SPE's slow-release delays antigen presentation. Both scenarios missed the critical window for coordinating with the expression of CD86, leading to either T cell apoptosis or suboptimal activation. In contrast, C10-SPE achieved a spatiotemporally synergetic effect of the MHC-I-peptide complex and co-stimulatory signal (CD86), leading to effective dendritic cell (DC) activation, enhanced T cell activation, and tumor regression in EG7-OVA bearing mice. Additionally, co-delivery of cytosine-phosphate-guanine (CpG) with SPE provided a sustained expression of the CD86 window for DC activation, improving the immune response and producing robust anti-tumor effects with C6-SPE comparable to C10-SPE. These findings highlight that synchronizing the spatiotemporal dynamics of antigen presentation and APC activation may confer an optimal strategy for enhanced vaccinations.

Octenyl succinic anhydride tigernut starch: Structure, physicochemical properties and stability of curcumin-loaded Pickering emulsion

In recent years, there has been increasing attention to starch particle-stabilized Pickering emulsions. In this study, the tigernut starch (TNS) was isolated from the tigernut meal, and further octenyl succinic anhydride tigernut starch (OSATNS) was prepared by a semi-dry method. The structure of OSATNS was analyzed and characterized by degrees of substitution (DS), contact angle, SEM, and FTIR. OSATNS was then used to stabilize the curcumin-loaded Pickering emulsion to improve the water solubility and stability of the curcumin. The results showed that OSATNS with 3 %–9 % OSA exhibited a DS range of 0.012 to 0.029, and its contact angle increased from 69.23° to 84.76°. SEM revealed that TNS consisted of small starch particles averaging 7.71 μm, and esterification did not significantly alter their morphology or size. FTIR analysis confirmed successful OSA incorporation by revealing two new peaks at 1732 cm−1 and 1558 cm−1. After 7 days of storage, Pickering emulsions stabilized with OSATNS-9 % exhibited superior stability and curcumin retention compared to Tween 80 emulsions, maintaining retention rates above 80 % even after different heat treatments. In conclusion, this study shows the potential application of OSATNS in stabilizing Pickering emulsions and demonstrates its good thermal stability and protection against curcumin during storage.

Demulsification of Pickering Emulsions by Chemical Dissolution of Stabilizers.

Demulsification of particle-stabilized oil-in-water emulsions is crucial in diverse fields such as treatment of produce water, recovery of valuable products of Pickering emulsion catalysis, and so on. In this work, we investigated a facile method for destabilizing emulsions by dissolving stabilizer particles by the introduction of acid or base. Nanoellipsoidal hematite-stabilized decane-in-water emulsions are destabilized by dissolving hematite with oxalic or hydrochloric acid in situ. Time required for complete demulsification decreased as the acid concentration is increased. The demulsification time is typically on the order of a few hours for the chosen protocol. Similarly, the silica-stabilized decane-water emulsion is demulsified by the addition of aqueous sodium hydroxide. Demulsification kinetics is presented as the temporal change of the emulsion volume with time. Emulsion volume decreases in two stages: an initial slow decrease followed by an exponential decrease. Scanning electron microscopy analysis shows that the stabilizing particles are completely dissolved and recrystallized as salts of respective kinds. An estimate of the desorption free energy suggests that particle size should be reduced to a few nanometers for inducing destabilization. This work describes a facile method to destabilize oil-in-water emulsion, and it can be generalized to any other particle-stabilized emulsions by choosing appropriate chemical reagent for dissolution.

Effects of different solid particle sizes on oat protein isolate and pectin particle-stabilized Pickering emulsions and their use as delivery systems

Oat protein isolate (OPI)/high methoxyl pectin (HMP) complexes (OPP) were prepared to stabilized Pickering emulsions and applied as nutraceutical delivery systems. The different mass ratios and pH changed the interactions between OPI and HMP that caused the different size of OPP. Specifically, smaller particle size of OPP (125.7–297.6 nm) were formed when hydrophobic interactions along with electrostatic forces predominant in OPP (OPI:HMP = 3:1, pH 4, 5). Among these particles, OPP-2 could stabilize Pickering emulsion efficiently through formation of dense interfacial film, which exhibited the highest apparent viscosity and the smallest average droplet size (23.39 μm). Moreover, OPP-2 stabilized Pickering emulsions with superior stability not only exhibited higher encapsulation efficiency of 85.63%, but also could control curcumin release in simulated gastrointestinal fluids to improve curcumin's bioaccessibility. These results verified the possibility of OPP to be a Pickering emulsions stabilizer, and also identified its potential to be a stable delivery system for bioactive compounds.

Agar-gelatin Maillard conjugates used for Pickering emulsion stabilization

A few protein- and polysaccharide-based particles have shown promising potential as stabilizers in multi-phase food systems. By incorporating polymer-based particles and modifying the wettability of colloidal systems, it is possible to create particle-stabilized emulsions with excellent stability. A Pickering emulsifier (AGMs) with better emulsifying properties was obtained by the Maillard reaction between acid-hydrolysed agar and gelatin. Laser confocal microscopy imaging revealed that AGMs particles can be used as solid emulsifiers to produce a typical O/W Pickering emulsion, with AGMs adsorbing onto the droplet surface to form a dense interfacial layer. Cryo-scanning electron microscopy analysis showed that AGMs self-assembled into a three-dimensional network structure, which prevented droplets aggregation through strong spatial site resistance, contributing to emulsion stabilization. These emulsions exhibited stability within a pH range of 1 to 11, NaCl concentrations not exceeding 300 mM, and at temperatures below 80 °C. The most stable emulsion oil-water ratio was 6:4 at a particle concentration of 0.75 % (w/v). AGMs-stabilized Pickering emulsion was utilized to create a semi-solid mayonnaise as a replacement for hydrogenated oil. Rheological analysis demonstrated that low-fat mayonnaise stabilized with AGMs exhibited similar rheological behavior to traditional mayonnaise, offering new avenues for the application of Pickering emulsions in the food industry.

Topical pickering emulsion versus classical excipients: A study of the residual film on the human skin

The interest in Pickering emulsions is based on the possibility of replacing classical emulsifiers with solid particles. These emulsions are very attractive in the pharmaceutical field for their stability virtues and as a vehicle to deliver active ingredients. The study aimed to analyze the properties of the residual film of the Pickering emulsions on the human skin compared to conventional systems.For this project, three types of solid particles were used: titanium dioxide, zinc oxide and silicon dioxide. All of them are capable of stabilizing the oil/water interface and thus forming totally emulsified systems. To create an emulsion of reference, a classical surfactant was used as an excipient. Complementary systems containing both particles and the emulsifier were also analyzed. Then, a combined approach between physicochemical and biometrological in vivo analysis was employed.The study proved that Pickering emulsions stabilized by the metal oxides were distinct from the reference emulsion in terms of droplet sizes and organization, rheological and textural responses. Consequently, it impacted the properties of the residual film once the product was applied to the skin. The particle-stabilized emulsions formed a hydrophobic film counter to conventional excipients.Also, the Friction parameter (or the roughness of the film) was directly linked to the quantity of the particles used in the formulation and their perception on the skin surface. The use of the particles blurs the glossy effect of the oil phase. Finally, it was observed that the appearance of the residual film was impacted by the type of the particle, namely TiO2 and ZnO particles.

Characteristics of Pickering emulsions stabilized by microgel particles of five different plant proteins and their application

Pickering emulsions stabilized by protein particles are of great interest for use in real food systems. This study was to investigate the properties of microgel particles prepared from different plant proteins, i.e., soybean protein isolate (SPI), pea protein isolate (PPI), mung bean protein isolate (MPI), chia seed protein isolate (CSPI), and chickpea protein isolate (CPI). MPI protein particles had most desirable Pickering emulsion forming ability. The particles of SPI and PPI had similar particle size (316.23 nm and 294.80 nm) and surface hydrophobicity (2238.40 and 2001.13) and emulsion forming ability, while the CSPI and CPI particle stabilized emulsions had the least desirable properties. The MPI and PPI particle stabilized Pickering emulsions produced better quality ice cream than the one produced by SPI particle-stabilized emulsions. These findings provide insight into the properties of Pickering emulsions stabilized by different plant protein particles and help expand their application in emulsions and ice cream.

In vitro digestion and colonic fermentation characteristics of media-milled purple sweet potato particle-stabilized Pickering emulsions.

Pickering emulsions stabilized by multicomponent particles have attracted increasing attention. Research on characterizing the digestion and health benefit effects of these emulsions in the human gastrointestinal tract are quite limited. This work aims to reveal the digestive characteristics of media-milled purple sweet potato particle-stabilized Pickering emulsions (PSPP-Es) during in vitro digestion and colonic fermentation. The media-milling process improved the in vitro digestibility and fermentability of PSPP-Es by reaching afree fatty acids release rate of 43.11 ± 4.61% after gastrointestinal digestion and total phenolic content release of 101.00 ± 1.44 μg gallic acid equivalents/mL after fermentation. In addition, PSPP-Es exhibited good antioxidative activity (2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays), α-glucosidase inhibitory activity (half-maximal inhibitory concentration: 6.70%, v/v), and prebiotic effects, reaching a total short-chain fatty acids production of 9.90 ± 0.12 mol L-1, boosting the growth of Akkermansia, Bifidobacterium, and Blautia and inhibiting the growth of Escherichia-Shigella. These findings indicate that the media-milling process enhances the potential health benefits of purple sweet potato particle-stabilized Pickering emulsions, which is beneficial for their application as a bioactive component delivery system in food and pharmaceutical products. © 2024 Society of Chemical Industry.

Enhancing the Thermal Stability of Zein Particle-Stabilized Aeratable Emulsions Through Genipin-Protein Cross-Linking and Its Possible Mechanism of Action.

Protein particle-stabilized emulsions often lack thermal stability, impacting their industrial use. This study investigated the effects of genipin (GP)-zein cross-linked particles with varying GP-to-protein weight ratios (0/0.02/0.1:1) on emulsion thermal stability. Enhanced stability was observed at the GP level of 0.1. Heat treatment increased the covalent cross-linking in raw particles and emulsions. Isolated particles from heated emulsions grew in size (micrometer scale) with higher GP levels, unlike heated raw particles (nanoscale). GP-protein cross-linking reduced the droplet-droplet and particle-emulsifier interactions in the heated emulsion. Spectroscopic analysis and electrophoresis revealed that GP-zein cross-linking increased protein structural stability and inhibited nondisulfide and non-GP cross-linking reactions in heated emulsions. The GP-zein bridges between particles at the oil-water interface create strong connections in the particle layer (shell), referred to as "particle-shell locking", enhancing the thermal stability of emulsion significantly. This insight aids the future design of protein-particle-based emulsions, preserving properties like aeratability during thermal processing.

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., –SO3-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{SO}}}_{3}^{-}$$\\end{document}) CNCs that were ionically crosslinked with alkaline-earth (i.e., Mg2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{Mg}}}^{2+}$$\\end{document}) or transition-d-block (i.e., Zn2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{Zn}}}^{2+}$$\\end{document}) 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.

The emulsifying performance of brewers' spent grains treated by colloid milling

The sustainable production of food ingredients can be achieved by utilising waste streams, but it is difficult to isolate pure components from a heterogeneous matrix. In this work, brewers' spent grains (BSG), which is a by-product from the brewing industry, was mildly treated with a colloid mill and its emulsifying ability was evaluated. The milled samples contained 26–32% protein and 52–62% fibre and were generally smaller than 10 μm. In its soluble fraction, a small amount of surface-active proteins was present and reduced oil-water interfacial tension by 35%. Emulsions prepared with the milled BSG and its insoluble particles were stable against coalescence for 10 days, with respective droplet sizes of 40 μm and 25 μm. The presence of fibres caused droplet flocculation but also helped to promote network formation. Our results suggest that obtaining pure components may not be necessary for emulsification purposes, especially for the case of particle-stabilised emulsions. Industrial relevanceIndustrial by-products from food processing are generated in large quantities and typically discarded due to their recalcitrant nature. Yet, there is more that can be exploited from this waste stream including proteins and fibres. Separation of these components in their purified form would require harsh methods that are not environmentally sustainable. This study provided insights into the use of a mild and scalable process that can produce functionally active dispersions that are of interest in the preparation of emulsions.

Anthocyanin-Rich Butterfly Pea Petal Extract Loaded Double Pickering Emulsion Containing Nanocrystalline Cellulose: Physicochemical Properties, Stability, and Rheology.

Butterfly pea petal extract (BPE)-loaded water-in-oil-in-water (W/O/W) emulsions were fabricated using nanocrystalline cellulose (NCC) as a hydrophilic stabilizer and polyglycerol polyricinoleate (PGPR) as a hydrophobic emulsifier. The impact of different concentrations of NCC and PGPR in different phase proportions on the emulsion formation, rheology, and stability of an anthocyanin-loaded (pH ≈ 7.0) emulsion was investigated. The mean droplet size of the emulsions increased as the NCC concentration increased, while color intensity (greenness) decreased as the PGPR and NCC concentrations increased. A microscopic examination confirmed that the NCC nanoparticles stabilized the inner W1/O phase, whereas the excess concentration of non-adsorbing NCC nanoparticles was suspended in the continuous aqueous phase. The rheological results showed that robust emulsion networks were formed when the NCC concentration increased. A network structure between the droplets and the development of the NCC network during the continuous phase were attributed to a gel-like behavior. Over the course of seven days, the emulsions with a higher proportion of NCC remained stable, as in samples 3%P-%N, 5%P-2%N, and 5%P@1%N, the total anthocyanin content decreased from 89.83% to 76.49%, 89.40% to 79.65, and 86.63% to 71.40%, respectively. These findings have significant implications for the accurate formulation of particle-stabilized double emulsions for anthocyanin delivery with higher stability.

Freeze-thaw stability of Pickering emulsion stabilized by modified soy protein particles and its application in plant-based ice cream

Pickering emulsions are of great interest to the food industry and their freeze-thaw stability important when used in frozen foods. Particles of soybean isolate (SPI) were heat treated and then crosslinked with transglutaminase (TG) enzyme to produce Pickering emulsions. The protein particles produced using unheated and uncrosslinked SPI (NSPI) was used as the benchmark. The mean particle size, absolute zeta potential, and surface hydrophobicity of protein particles produced using heat treatment and TG crosslinking (at 40 U/g) SPI (HSPI-TG-40) were the highest and substantially higher than those produced using NSPI. The thermal treatment of protein particles followed by crosslinking with TG enzyme improved the freeze-thaw stability of Pickering emulsions stabilized by them. The Pickering emulsions produced using HSPI-TG-40 had the lowest temperature for ice crystal formation and they had better freeze-thaw stability. The plant-based ice cream prepared by HSPI-TG-40 particle-stabilized Pickering emulsions had suitable texture and freeze-thaw stability compared to the ice cream produced using NSPI. The Pickering particles produced using heat treatment of SPI followed by crosslinking with TG (at 40 U/g) produced the most freeze-thaw stable Pickering emulsions. These Pickering particles and Pickering emulsions could be used in frozen foods such as ice cream.

Thermal Stability Improvement of Core Material via High Internal Phase Emulsion Gels.

Biocompatible particle-stabilized emulsions have gained significant attention in the biomedical industry. In this study, we employed dynamic high-pressure microfluidization (HPM) to prepare a biocompatible particle emulsion, which effectively enhances the thermal stability of core materials without the addition of any chemical additives. The results demonstrate that the HPM-treated particle-stabilized emulsion forms an interface membrane with high expansion and viscoelastic properties, thus preventing core material agglomeration at elevated temperatures. Furthermore, the particle concentration used for constructing the emulsion gel network significantly impacts the overall strength and stability of the material while possessing the ability to inhibit oxidation of the thermosensitive core material. This investigation explores the influence of particle concentration on the stability of particle-stabilized emulsion gels, thereby providing valuable insights for the design, improvement, and practical applications of innovative clean label emulsions, particularly in the embedding and delivery of thermosensitive core materials.

Ultrasonic and homogenization: An overview of the preparation of an edible protein-polysaccharide complex emulsion.

Emulsion systems are extensively utilized in the food industry, including dairy products, such as ice cream and salad dressing, as well as meat products, beverages, sauces, and mayonnaise. Meanwhile, diverse advanced technologies have been developed for emulsion preparation. Compared with other techniques, high-intensity ultrasound (HIUS) and high-pressure homogenization (HPH) are two emerging emulsification methods that are cost-effective, green, and environmentally friendly and have gained significant attention. HIUS-induced acoustic cavitation helps in efficiently disrupting the oil droplets, which effectively produces a stable emulsion. HPH-induced shear stress, turbulence, and cavitation lead to droplet disruption, altering protein structure and functional aspects of food. The key distinctions among emulsification devices are covered in this review, as are the mechanisms of the HIUS and HPH emulsification processes. Furthermore, the preparation of emulsions including natural polymers (e.g., proteins-polysaccharides, and their complexes), has also been discussed in this review. Moreover, the review put forward to the future HIUSand HPH emulsification trends and challenges. HIUS and HPH can prepare much emulsifier-stable food emulsions, (e.g., proteins, polysaccharides, and protein-polysaccharide complexes). Appropriate HIUS and HPH treatment can improve emulsions' rheological and emulsifying properties and reduce the emulsions droplets' size. HIUS and HPH are suitable methods for developing protein-polysaccharide forming stable emulsions. Despite the numerous studies conducted on ultrasonic and homogenization-induced emulsifying properties available in recent literature, this review specifically focuses on summarizing the significant progress made in utilizing biopolymer-based protein-polysaccharide complex particles, which can provide valuable insights for designing new, sustainable, clean-label, and improved eco-friendly colloidal systems for food emulsion. PRACTICAL APPLICATION: Utilizing complex particle-stabilized emulsions is a promising approach towards developing safer, healthier, and more sustainable food products that meet legal requirements and industrial standards. Moreover, the is an increasing need of concentrated emulsions stabilized by biopolymer complex particles, which have been increasingly recognized for their potential health benefits in protecting against lifestyle-related diseases by the scientific community, industries, and consumers.

Co-stabilization mechanisms of solid particles and soluble compounds in hybrid Pickering emulsions stabilized by unrefined apple pomace powder

Vegetal by-product powders, such as apple pomace powder, represent an efficient green alternative to conventional emulsifiers to stabilize oil-in-water Pickering emulsions. The natural material being used without purification, its multiple components shall impact differently the emulsion stability and interact with each other. These effects might be either synergic, competitive, or both depending on their ratio. Herein, the co-stabilizing effects of the apple pomace compounds on Pickering emulsions were explored from microscopic to macroscopic scales. The apple pomace powder was first fragmented into several fractions which were characterized (particle sizes, shape and wettability, oil-water surface activity). Emulsions were then prepared by varying the stabilizing material composition using the different fractions obtained from the apple powder. Emulsions properties (droplet size, rheological properties) and stability were monitored over a month. The key role of solid particles in the surface activity of the apple pomace powder was shown by interfacial tension measurements. All particle-stabilized emulsions were stable against coalescence during storage despite high droplet diameters (up to 80 μm) and low surface coverage. Soluble matter and particles show a synergic behavior to stabilize oil-in-water emulsions. The soluble matter drives droplet size whereas insoluble cellulosic particles are responsible for emulsion stability by both Pickering adsorption to the oil droplet and oil droplet trapping in a three-dimensional network. This study provides new insights into the understanding of natural powders stabilizing mechanisms that may lead to a better prediction of the potential of vegetal by-products as stabilizing agents from their chemical composition.

In vitro gastrointestinal digestion and colonic fermentation of media-milled black rice particle-stabilized Pickering emulsion: Phenolic release, bioactivity and prebiotic potential

This is a pioneer study that investigated the digestive characteristics of Pickering emulsions stabilized by media-milled black rice particles during in vitro digestion and colonic fermentation. Free fatty acid release of the emulsions improved from 28.42 ± 3.13% to 33.68 ± 4.05% after media milling. The phenolics released from media-milled sample were close to those from unground sample. Media-milled sample exhibited higher DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging ability and α-glucosidase inhibition rate than unground sample. Media milling increased the generation of short-chain fatty acids (SCFAs) during colonic fermentation, especially acetic acid (23% improvement in media-milled sample over unground sample). It also inhibited the growth of harmful bacteria namely Escherichia Shigella and Streptococcus, and promoted the growth of beneficial bacteria including Bifidobacterium and Blautia. These findings revealed that media-milled black rice particle-stabilized Pickering emulsions possessed intrinsic bioactivity and prebiotic potentials in the gastrointestinal tract for the first time.

Pickering emulsions stabilized by soybean protein isolate/chitosan hydrochloride complex and their applications in essential oil delivery

In this work, fabrication of soybean protein isolate (SPI)/chitosan hydrochloride (CHC) composite particles stabilized O/W Pickering emulsions using soybean oil as an oil phase was optimized by examining the effects of pH, SPI/CHC mass ratio, SPI/CHC composite particle concentration and oil phase fraction on the stability of the emulsions. The results showed that under the conditions of SPI/CHC mass ratio 1:1, pH 4 and particle concentration 2 %, the SPI/CHC composite particles could stabilize the emulsions with oil phase fraction up to 80 %. At an oil phase fraction of 60 %, the emulsions had a minimum particle size. The microstructure, storage and oxidation stabilities and rheological properties of the emulsions were determined. Using this SPI/CHC composite particle-stabilized Pickering emulsion template, citrus essential oil (CEO) Pickering emulsion (CEOP) was prepared. CEOP was found to markedly inhibit two food-related microorganisms, Staphylococcus aureus and Escherichia coli. In addition, the CEOP emulsion dilution (containing 4500 μL CEO/L) not only improved the water solubility of CEO, but also effectively retarded the browning and bacterial growth of fresh-cut apple. The SPI/CHC-stabilized Pickering emulsion template constructed in this work provides a promising alternative for the delivery of antimicrobial essential oils in the food industry.

Particle Size and Rheology of Silica Particle Networks at the Air-Water Interface.

Silica nanoparticles find utility in different roles within the commercial domain. They are either employed in bulk within pharmaceutical formulations or at interfaces in anti-coalescing agents. Thus, studying the particle attributes contributing to the characteristics of silica particle-laden interfaces is of interest. The present work highlights the impact of particle size (i.e., 250 nm vs. 1000 nm) on the rheological properties of interfacial networks formed by hydrophobically modified silica nanoparticles at the air-water interface. The particle surface properties were examined using mobility measurements, Langmuir trough studies, and interfacial rheology techniques. Optical microscopy imaging along with Langmuir trough studies revealed the microstructure associated with various surface pressures and corresponding surface coverages (ϕ). The 1000 nm silica particle networks gave rise to a higher surface pressure at the same coverage compared to 250 nm particles on account of the stronger attractive capillary interactions. Interfacial rheological characterization revealed that networks with 1000 nm particles possess higher surface modulus and yield stress in comparison to the network obtained with 250 nm particles at the same surface pressure. These findings highlight the effect of particle size on the rheological characteristics of particle-laden interfaces, which is of importance in determining the stability and flow response of formulations comprising particle-stabilized emulsions and foams.