Pickering emulsions stabilized by whey protein nanoparticles prepared by thermal cross-linking

Optimizing anthocyanin Oral delivery: Effects of food biomacromolecule types on Nanocarrier performance for enhanced bioavailability

Wall material types influence the efficacy of nanocarriers in oral delivery systems. We utilized three food biomacromolecules (whey protein isolate, oxidized starch, lipids) to prepare three types of nanocarriers. Our aim was to investigate their performance in digestion, cellular absorption, mucus penetration, intestinal retention, and bioavailability of the encapsulated anthocyanins (Ant). The release rate of protein nanocarriers (Pro-NCs) was twice that of starch nanocarriers (Sta-NCs) and four times that of lipid nanocarriers (Lip-NCs) in simulated gastrointestinal fluid. Additionally, Pro-NCs demonstrated superior transmembrane transport capacity and over three times cellular internalization efficiency than Sta-NCs and Lip-NCs. Sta-NCs exhibited the highest mucus-penetrating capacity, while Pro-NCs displayed the strongest mucoadhesion, resulting in extended gastrointestinal retention time for Pro-NCs. Sta-NCs significantly enhanced the in vivo bioavailability of Ant, nearly twice that of free Ant. Our results demonstrate the critical role of wall material types in optimizing nanocarriers for the specific delivery of bioactive compounds.

Understanding Stabilization of Oil-in-Water Emulsions with Pea Protein─Studies of Structure and Properties

This study investigates the stability and structure of oil-in-water emulsions stabilized by pea protein. Of the wide range of emulsion compositions explored, a region of stability at a minimum of 5% w/v pea protein and 30-50% v/v oil was determined. This pea protein concentration is more than what is needed to form a layer covering the interface. X-ray scattering revealed a thick, dense protein layer at the interface as well as hydrated protein dispersed in the continuous phase. Shear-thinning behavior was observed, and the high viscosity in combination with the thick protein layer at the interface creates a good stability against creaming and coalescence. Emulsions in a pH range from acidic to neutral were studied, and the overall stability was observed to be broadly similar independently of pH. Size measurements revealed polydisperse protein particles. The emulsion droplets are also very polydisperse. Apart from understanding pea protein-stabilized emulsions in particular, insights are gained about protein stabilization in general. Knowledge of the location and the role of the different components in the pea protein material suggests that properties such as viscosity and stability can be tailored for various applications, including food and nutraceutical products.

Characterization of high-internal-phase emulsions based on soy protein isolate with varying concentrations of soy hull polysaccharide and their capabilities for probiotic delivery: In vivo and in vitro release and thermal stability

In this study, the impact of soy hull polysaccharide (SHP) concentration on high-internal-phase emulsions (HIPEs) formation and the gastrointestinal viability of Lactobacillus plantarum within HIPEs were demonstrated. Following the addition of SHP, competitive adsorption with soy protein isolate (SPI) occurred, leading to increased protein adhesion to the oil-water interface and subsequent coating of oil droplets. This process augmented viscosity and enhanced HIPEs stability. Specifically, 1.8 % SHP had the best encapsulation efficiency and delivery efficiency, reaching 99.3 % and 71.1 %, respectively. After 14 d of continuous zebrafishs feeding, viable counts of Lactobacillus plantarum and complex probiotics in the intestinal tract was 1.1 × 107, 1.3 × 107, respectively. In vitro experiments further proved that HIPEs' ability to significantly enhance probiotics' intestinal colonization and provided targeted release for colon-specific delivery. These results provided a promising strategy for HIPEs-encapsulated probiotic delivery systems in oral food applications.

Novel Pickering emulsion stabilized by glycosylated whey protein isolate: Characterization, stability, and curcumin bioaccessibility

Pickering emulsions prepared from protein-polysaccharide complexes have attracted increasing attention. In this study, whey protein isolates (WPI) were modified with oligochitosan using transglutaminase (TGase)-type to fabricate Pickering emulsions, and loaded with curcumin. The curcumin/protein ratio of 1:25 and oil phase fraction (φ = 17 %) are the most optimal condition for emulsions stabilization, and particle size of glycosylated WPI emulsion was 31.70 μm. Glycosylated WPI emulsion had the highest encapsulation efficiency (96.64 %) of curcumin. Microstructure analysis showed that glycosylated WPI had small droplets covered by dense interface layers. The modified WPI emulsions exhibited optimal emulsifying properties and emulsion stability, which effectively inhibited the premature water-oil stratification in emulsion. In vitro digestion results showed that WPI-oligochitosan complexes enhanced curcumin bioaccessibility (40.34 %). The antioxidant activity of glycosylated WPI emulsions was significantly increased. The results of this study provide helpful references for applying glycosylated WPI-stabilized Pickering emulsions, which can be used as transport carriers of curcumin.

Pickering emulsions stabilized by cellulose nanocrystals extracted from hazelnut shells: Production and stability under different harsh conditions

Cellulose nanocrystals (CNCs) are biodegradable particles that have emerged as promising stabilizers for Pickering emulsions. This study investigated the effectiveness of CNCs in forming the Pickering emulsion from hazelnut shells (HS), an agricultural waste. Following the alkaline and bleaching treatments applied to HS, CNCs were obtained from treated hazelnut shell with acid hydrolysis. The physicochemical characteristics of CNCs were investigated using dynamic light scattering, XRD, FTIR, SEM, and TEM. A high crystalline (69.6 %) CNCs with a spherical shape were obtained. Contact angle and interfacial tension tests were conducted and showed that CNCs had amphiphilic nature. Pickering emulsions were investigated for their size, zeta potential, and stability under varying CNC concentrations. The results showed that when CNCs concentration increased from 0.5 to 2.0 wt%, droplet diameter decreased approximately 1.8 times and zeta potential increased. Creaming was not observed during 28 days of storage in a concentration of 2.0 wt% CNCs. The CNC stabilized emulsions exhibited high stability within a range of pH, temperatures, and salt concentrations. This study demonstrated that CNCs extracted from HS as environmentally friendly and cost-effective materials, could serve as a new stabilizer for Pickering emulsions especially for high temperature and low pH sensitive products such as mayonnaise.

The influence of α and α' subunits on SPI Pickering emulsions based on natural hybrid breeding varieties

In this study, food-grade protein nanoparticles (Wild-NPs, α-lack-NPs, α'-lack-NPs, and (α + α')-lack-NPs) were organized as emulsion stabilizers via thermal induction. The effects of α and α' subunits in soybean protein isolate (SPI) on Wild nanoparticle Pickering emulsion (Wild-NPPEs), α-lack nanoparticle Pickering emulsion (α-lack-NPPEs), α'-lack nanoparticle Pickering emulsion (α'-lack-NPPEs) and (α + α')-lack nanoparticle Pickering emulsion ((α + α')-lack-NPPEs) were investigated. The Pickering emulsion stabilization mechanism indicated that the α'-lack-NPs particle size, surface hydrophobicity, and contact angle were mostly comparatively large. Therefore, the absence of the α' subunit made the desorption of protein nanoparticles at the oil and water interface require higher energy. Through the hydrophobic interaction between molecules, the structure and properties of the emulsion were improved, showing good stability. The existence of α'-lack-NPPEs leads to the formation of a gel-like network in the emulsion, which increases the viscosity of the emulsion and makes the network structure of the emulsion more uniform and denser.

Changes in emulsifying properties of caseinate-Soy soluble polysaccharides conjugates by ultrasonication

This research aimed to assess the impact of ultrasonication on the emulsifying ability of a conjugate system composed of sodium caseinate and soluble soy polysaccharides. The study analyzed the characteristics of the particles and evaluated the emulsions produced using nanoconjugates. The results showed that ultrasonication improved the contact angle (63.7°) and decreased particle size (75 nm), resulting in more effective emulsifying efficiency. At a 2 % concentration of the nanoconjugates, stable emulsions with a 50 % oil content were successfully formed through complete coverage of the droplets' surface, and no oil release was observed. Moreover, the emulsions' creaming index remained below 25 % even after 60 days of storage. The stability of the nanoconjugate-based emulsions depended on the concentration of nanoconjugates, with an optimal concentration of 4 %. These findings suggest that the nanoconjugates have great potential as a natural stabilizer for emulsion-based products.

Effects of Pre-Emulsification with Thermal-Denatured Whey Protein on Texture and Microstructure of Reduced-Sodium Processed Cheese

Thermal-denatured whey protein-milk fat emulsion gels with different degrees of pre-emulsification were prepared by pre-emulsifying milk fat with thermal-denatured whey protein and used in the preparation of reduced-sodium processed cheeses. The effect of the thermal-denatured whey protein pre-emulsification process on the texture and microstructure of reduced-sodium processed cheeses was evaluated by studying the composition, color, texture, functional properties, microstructure and sensory analysis of the processed cheeses. The results showed that compared with cheese without pre-emulsified fat (1.5% ES control), the moisture content of cheese with pre-emulsified 100% fat (1.5% ES100) increased by 5.81%, the L* values increased by 7.61%, the hardness increased by 43.24%, and the free oil release decreased by 38%. The microstructure showed that the particle size of fat was significantly reduced, and the distribution was more uniform. In addition, compared with the cheese added with 3% emulsifying salt (3% ES control), the amount of emulsifying salt in the 1.5% ES100 decreased by 50%, but the fat distribution of the two kinds of cheese tended to be consistent, and there was no obvious change in texture characteristics and meltability. Sensory scores increased with the increase in pre-emulsification degree. Overall, the pre-emulsification of milk fat with thermal-denatured whey protein can reduce the sodium content of processed cheese and improve its quality.

Designing ultra-stable linseed oil-in-water Mickering emulsions using whey protein isolate cold-set microgels containing marjoram aqueous extract: Effect of pH and extract on rheological, physical, and chemical properties

In this study, whey protein isolate (WPI) cold-set microgels containing marjoram (Origanum majorana) aqueous extract (MAE) were prepared at different pHs (4.0, 5.0, and 6.0). After characterization, the microgel dispersion was used to stabilize linseed oil-in-water Mickering emulsions (MEs). The resultant MEs were then characterized in terms of physicochemical and rheological properties under the effect of pH and MAE addition. The morphology, particle size, zeta potential, and interfacial tension of microgels were affected by pH and MAE. XRD patterns showed the amorphous structure. Microgel-stabilized MEs did not reveal any significant sign of instability under gravity during 6 months of storage. All MEs had dominant elastic character. Despite the lowest zeta potential values, MEs prepared at pH 4 showed the highest physical stability against gravity but the lowest centrifugal stability against oiling off, which indicated that both viscous and elastic components are required for MEs stability. This sample had the highest apparent viscosity and the strongest viscoelastic properties. Rheological data were best fitted with Herschel-Bulkley and Power Law models. An increase in pH and presence of MAE improved the oxidative stability of MEs. The results of this study showed that WPI microgels are appropriate candidate for long-term stabilization of linseed oil-in-water MEs. The presence of MAE is useful in designing special emulsions in which the aqueous phase is partially replaced by the aqueous extract of medicinal plants.

Pickering emulsions stabilized with a spirulina protein-chitosan complex for astaxanthin delivery

Astaxanthin (AXT) is a lipid-soluble carotenoid with good anti-oxidation, hepatic steatosis reduction, anti-inflammation, and intestinal microbiota regulation ability, whose poor stability and pH vulnerability limit its bioavailability. Spirulina protein (SP) derived from spirulina has good emulsifying ability with potential application in nutraceuticals, medicines, and cosmetics. In this study, Pickering emulsions were prepared using a SP-chitosan (CS) complex as an emulsifier. The particle size, zeta potential, and three-phase contact angle of the SP-CS complex with different SP to CS ratios were investigated. A mass ratio of 1 : 2.5 SP-CS complex showed a good emulsifying ability in preparing Pickering emulsion. A higher storage modulus and viscoelasticity were observed with higher SP-CS complex concentrations and oil fractions. The SP-CS Pickering emulsion significantly improved the stability of AXT in different environments. The lipid release rate and AXT bioavailability after digestion of 3 wt% SP-CS complex-stabilized Pickering emulsion reached 70.54 ± 1.59% and 36.60 ± 3.44%, respectively. The results indicated that the SP-CS complex could act as a Pickering emulsion stabilizer and had the potential to deliver protective hydrophobic AXT.

Demulsification of water-in-oil emulsions stabilized with glycerol monostearate crystals

HYPOTHESIS

Colloidal particles can be used to generate water-in-oil (W/O) emulsions resistant against coalescence. Demulsification is possible with addition of low molecular weight surfactants to the emulsion continuous oil phase. Whether surfactants demulsify particle-stabilized W/O emulsions depends on their ability to modify the wettability of interfacially-bound particles.

EXPERIMENTAL

Crystals of glycerol monostearate (GMS) were prepared followed by water addition to generate GMS-stabilized W/O emulsions. The surfactants sorbitan monooleate (SMO), sorbitan monolaurate (SML), citric acid esters of monoglycerides (CITREM), sorbitan trioleate (STO), propylene glycol monolaurate (PgML), and polyglycerol polyricinoleate (PGPR) were added to the emulsion oil phase. Emulsion microstructure was characterized by light microscopy and cryo-scanning electron microscopy. Surfactant activity and crystal wetting were characterized by interfacial tension and three-phase contact angle measurements. Salt release from within the emulsions was used to assess demulsifier efficacy.

FINDINGS

Emulsions stabilized by platelet-like GMS crystals were generated. Of the six surfactants, SMO, SML, and CITREM were effective demulsifiers whereas STO, PgML, and PGPR were ineffective. The former three sufficiently modified the wettability of GMS crystals on the droplet surface, as they adsorbed to both the oil-water interface and GMS crystal surface. Emulsion destabilization was associated with faster NaCl release from the emulsion internal phase.

Effect of salt treatment on the stabilization of Pickering emulsions prepared with rice bran protein

In this study, salt addition (NaCl and CaCl₂) was utilized to improve the stability of emulsions formed by rice bran protein (RBP). The result showed that salt addition improved the adsorption of protein on the oil-water interface and enhanced the physical stability of emulsions. Compared to NaCl condition, emulsions with CaCl₂ (especially 200 mM) addition exhibited more significant storage stability, as microscopy images showed emulsion structure unchanged and droplet size increasing slightly from 12.02 µm to 16.04 µm in 7 days. It was attributed to the strengthened particle complexation with CaCl₂ and the increased hydrophobic interactions, which is explained by the improved particle size (260.93 nm), surface hydrophobicity (1890.10) and fluorescence intensity, thus inducing dense and hardly destroyed interfacial layers. Rheological behavior analyses suggested that salt-induced emulsions had higher viscoelasticity and maintained a stable gel-like structure. The result of study explored the mechanism of salt treated protein particles, developed a further understanding of Pickering emulsion, and was beneficial to the application of RBP.

Biopolymer- and Lipid-Based Carriers for the Delivery of Plant-Based Ingredients

Natural ingredients are gaining increasing attention from manufacturers following consumers’ concerns about the excessive use of synthetic ingredients. However, the use of natural extracts or molecules to achieve desirable qualities throughout the shelf life of foodstuff and, upon consumption, in the relevant biological environment is severely limited by their poor performance, especially with respect to solubility, stability against environmental conditions during product manufacturing, storage, and bioavailability upon consumption. Nanoencapsulation can be seen as an attractive approach with which to overcome these challenges. Among the different nanoencapsulation systems, lipids and biopolymer-based nanocarriers have emerged as the most effective ones because of their intrinsic low toxicity following their formulation with biocompatible and biodegradable materials. The present review aims to provide a survey of the recent advances in nanoscale carriers, formulated with biopolymers or lipids, for the encapsulation of natural compounds and plant extracts.

Stability of protein particle based Pickering emulsions in various environments: review on strategies to inhibit coalescence and oxidation

The emerging research interests in fabrication of protein particles as soft-particle emulsifiers show the prospective potential of using protein particles in novel poly-phase dispersing food systems. This review first provides a comprehensive summary and analysis on the dominant role of key physicochemical properties of protein particles including wettability, morphology, surface charge and protein concentration on their emulsifying abilities to construct Pickering emulsions. It was found that the constructed emulsions showed high sensitivity to changes in pH, ionic strength and temperature (thermal and freeze-thaw treatment). Moreover, oxidation remains as a challenge for protein particle based Pickering emulsions during prolonged storage, reducing their acceptance in food products. Current strategies for improving the stability of these emulsions to variable aqueous conditions and variable temperatures, and restricting oxidation event are summarized. In summary, an "ideal" protein particle-based Pickering emulsion system is proposed, encompassing aspects of interfacial property, emulsion network and texture, and antioxidant enrichment, thus promoting industrial translation into novel food and nutraceutical products.

Improving the physicochemical stability of Pickering emulsion stabilized by glycosylated whey protein isolate/cyanidin-3-glucoside to deliver curcumin

Protein-polysaccharide-polyphenol delivery systems function as a promising tool to deliver bioactive ingredients aiming to improve their solubility and bioavailability. In this study, whey protein isolate (WPI), short-chain inulin (SCI), and cyanidin-3-glucoside (C3G) were first used to stabilize Pickering emulsions. The physicochemical properties and stability of curcumin encapsulated or not in Pickering emulsions were explored. Results showed that glycosylation and C3G reduced surface and interfacial tension on protein surfaces and inhibited the aggregation of emulsion droplets, thereby reducing the emulsion's particle size. WPI-SCI/C3G stabilized Pickering emulsion had the best stability. The CLSM results showed that the WPI-SCI and WPI-SCI/C3G stabilized emulsions were uniformly dispersed, suggesting that glycosylation and the interaction between protein and C3G enhanced the adsorption capacity of the interfacial protein and improved the stability of the Pickering emulsion. The retention rates of curcumin-loaded WPI-SCI- (67.34 %) and WPI-SCI/C3G- (77.07 %) stabilized Pickering emulsions on day 8 of storage were higher than those in WPI- (33.97 %) and WPI/C3G- (37.02 %) stabilized emulsions, and the degradation half-life was also extended from 7 days to >15 days. These findings provide a theoretical basis for the application of WPI Pickering emulsion and indicate a useful means for the delivery of bioactive components.

Structure and properties of Pickering emulsions stabilized solely with novel buckwheat protein colloidal particles

In this paper, buckwheat protein colloidal particles (BPCPs) were prepared by heat treatment to stabilize oil-water interface. The results of particle size, surface hydrophobicity and wettability indicated that the prepared BPCPs could be used as novel Pickering emulsifier. The effects of BPCPs concentration, ionic strength and heat treatment on the structure and properties of Pickering emulsions were explored. The microstructure results showed that BPCPs could tightly coated on the surface of oil droplets to form a tight interfacial film, confirming that BPCPs could be used as an effective Pickering-like stabilizer. With the increase of BPCPs concentration, the droplet size of the Pickering emulsion gradually decreased, and the viscoelasticity and storage stability of the emulsion were effectively improved. Different from the effect of ionic strength, heat treatment was beneficial to increasing the viscoelasticity of BPCPs-stabilized Pickering emulsion. The Pickering emulsions exhibited certain flocculation at different temperatures and ionic strengths, while still maintained good solid-like behavior. These results suggest that the structure and properties of BPCPs-stabilized Pickering emulsion could be regulated by changing the ionic strength and temperature.

Research Progress of Food-Grade High Internal Phase Pickering Emulsions and Their Application in 3D Printing

High internal phase Pickering emulsion (HIPPE) is a type of emulsion stabilized by solid particles irreversibly adsorbed on an interfacial film, and the volume fraction of the dispersed phase (Φ) is larger than the maximum packing volume fraction (Φ_max). Proteins, polysaccharides, and their composite particles can be used as good particle stabilizers. The contact angle can most intuitively demonstrate the hydrophilicity and hydrophobicity of the particles and also determines the type of emulsions (O/W or W/O type). Particles' three-phase contact angles can be adjusted to about 90° by compounding or modification, which is more conducive to emulsion stability. As a shear thinning pseudoplastic fluid, HIPPE can be extruded smoothly through 3D printer nozzles, and its high storage modulus can support the structure of printed products. There is huge potential for future applications in 3D printing of food. This work reviewed the biomacromolecules that can be used to stabilize food-grade HIPPE, the stabilization mechanism of the emulsions, and the research progress of food 3D printing to provide a reference for the development of advanced food products based on HIPPE.

Novel Biopesticides Based on Nanoencapsulation of Azadirachtin with Whey Protein to Control Fall Armyworm

Biopesticides have become a global trend in order to minimize the hazards derived from synthetic chemical pesticides and improve the safety, efficacy, and environmental friendliness of agricultural pest management. Herein, we report a novel biopesticide composite encapsulating azadirachtin with the size of 260.9 ± 6.8 nm and its effects on the insect pest Spodoptera frugiperda (fall armyworm). The nanocomposite biopesticide was produced via nano emulsification and freeze-drying process using whey protein isolate as a nanocarrier matrix to encapsulate azadirachtin, a natural insect-killing compound obtained from neem seed. We found that the nanocomposite biopesticide acted quicker and with greater efficacy than bulk azadirachtin treatment with corresponding LC₅₀ values within 11 days of S. frugiperda larvae survival. Through confocal microscopy, we found the enhanced biodistribution of the nanocomposite to all parts of the insect body. Photodegradation assays revealed an enhanced UV stability facilitated by light-scattering stemming from the intrinsic nanostructure and UV scavenging vitamin-E component.

Squalene-Rich Amaranth Oil Pickering Emulsions Stabilized by Native α-Lactalbumin Nanoparticles

The stabilization of Pickering emulsions by nanoparticles has drawn great interest in the field of food science and technology. In this study, α-Lactalbumin nanoparticles prepared by the desolvation and cross-linking method from protein solutions with initial pH values of 9 and 11 were used to stabilize squalene-rich amaranth oil Pickering o/w emulsions. The effect of different concentrations of nanoparticles on the size, size distribution, ζ potential, and emulsion stability was evaluated using dynamic light scattering, electron microscopy, and light backscattering. Dependence of the emulsions’ droplet size on the nanoparticle concentration was observed, and the critical coverage ratio was reached when 5–10% nanoparticles concentration was used. Our findings suggest that α-LA nanoparticles at a 10% concentration can be used as novel stabilizers for Pickering emulsions to provide protection for beneficial lipophilic bioactive compounds. This is the first time that native α-LA nanoparticles have been used as stabilizers of Pickering emulsions.

Effect of Fibril Entanglement on Pickering Emulsions Stabilized by Whey Protein Fibrils for Nobiletin Delivery

The aim of the study was to investigate the effects of whey protein isolate (WPI) fibrils entanglement on the stability and loading capacity of WPI fibrils-stabilized Pickering emulsion. The results of rheology and small-angle X-ray scattering (SAXS) showed the overlap concentration (C*) of WPI fibrils was around 0.5 wt.%. When the concentration was higher than C*, the fibrils became compact and entangled in solution due to a small cross-sectional radius of gyration value (1.18 nm). The interfacial behavior was evaluated by interfacial adsorption and confocal laser scanning microscopy (CLSM). As the fibril concentration increased from 0.1 wt.% to 1.25 wt.%, faster adsorption kinetics (from 0.13 to 0.21) and lower interfacial tension (from 11.85 mN/m to 10.34 mN/m) were achieved. CLSM results showed that WPI fibrils can effectively absorb on the surface of oil droplets. Finally, the microstructure and in vitro lipolysis were used to evaluate the effect of fibrils entanglement on the stability of emulsion and bioaccessibility of nobiletin. At C* concentration, WPI fibrils-stabilized Pickering emulsions exhibited excellent long-term stability and were also stable at various pHs (2.0–7.0) and ionic strengths (0–200 mM). WPI fibrils-stabilized Pickering emulsions after loading nobiletin remained stable, and in vitro digestion showed that these Pickering emulsions could significantly improve the extent of lipolysis (from 36% to 49%) and nobiletin bioaccessibility (21.9% to 62.5%). This study could provide new insight into the fabrication of food-grade Pickering emulsion with good nutraceutical protection.

Pickering Emulsions Stabilized by Tea Water-Insoluble Protein Nanoparticles From Tea Residues: Responsiveness to Ionic Strength

Tea water-insoluble protein nanoparticles (TWIPNs) can be applied to stabilize Pickering emulsions. However, the effect of ionic strength (0–400 mmol/L) on the characteristics of Pickering emulsions stabilized by TWIPNs (TWIPNPEs) including volume-averaged particle size (d_4,3), zeta potential, microstructure and rheological properties is still unclear. Therefore, this work researched the effect of ionic strength on the characteristics of TWIPNPEs. The d_4,3 of TWIPNPEs in the aquatic phase increased with the increase in ionic strength (0–400 mmol/L), which was higher than that in the SDS phase. Furthermore, the flocculation index of TWIPNPEs significantly (P < 0.05) increased from 24.48 to 152.92% with the increase in ionic strength. This could be verified from the microstructure observation. These results indicated that ionic strength could promote the flocculation of TWIPNPEs. Besides, the absolute values of zeta potential under different ionic strengths were above 40 mV in favor of the stabilization of TWIPNPEs. The viscosity of TWIPNPEs as a pseudoplastic fluid became thin when shear rate increased from 0.1 to 100 s⁻¹. The viscoelasticity of TWIPNPEs increased with increasing ionic strength to make TWIPNPEs form a gel-like Pickering emulsion. the possible mechanism of flocculation stability of TWIPNPEs under different ionic strengths was propose. TWIPNs adsorbed to the oil-water interface would prompt flocculation between different emulsion droplets under the high ionic strength to form gel-like behavior verified by CLSM. These results on the characteristics of TWIPNPEs in a wide ionic strength range would provide the theoretical basis for applying Pickering emulsions stabilized by plant proteins in the food industry.

Nano- and microparticle-stabilized Pickering emulsions designed for topical therapeutics and cosmetic applications

Pickering emulsions are systems composed of two immiscible fluids, which are stabilized by solid organic or inorganic particles. These solid particles include a broad range of particles that can be used to stabilize Pickering emulsions. An improved resistance against coalescence and lower toxicity, against conventional emulsions stabilized by surfactants, make Pickering emulsions suitable candidates for numerous applications, such as catalysis, food, oil recovery, cosmetics, and pharmaceutical industries. In this article, we give an overview of Pickering emulsions focusing on topical applications. First, we reference the parameters that influence the stabilization of Pickering emulsions. Second, we discuss some of the already investigated topical applications of nano- and microparticles used to stabilize Pickering emulsions. Afterwards, we consider some of the most promising stabilizers of Pickering emulsions for topical applications. Ultimately, we carried out a brief analysis of toxicity and advances in future perspectives, highlighting the promising use of these emulsions in cosmetics and dermopharmaceutical formulations.

Recent progress in Pickering emulsions stabilised by bioderived particles

In recent years, the demand for non-surfactant based Pickering emulsions in many industrial applications has grown significantly because of the option to select biodegradable and sustainable materials with low toxicity as emulsion stabilisers. Usually, emulsions are a dispersion system, where synthetic surfactants or macromolecules stabilise two immiscible phases (typically water and oil phases) to prevent coalescence. However, synthetic surfactants are not always a suitable choice in some applications, especially in pharmaceuticals, food and cosmetics, due to toxicity and lack of compatibility and biodegradability. Therefore, this review reports recent literature (2018-2021) on the use of comparatively safer biodegradable polysaccharide particles, proteins, lipids and combinations of these species in various Pickering emulsion formulations. Also, an overview of the various tuneable factors associated with the functionalisation or surface modification of these solid particles, that govern the stability of the Pickering emulsions is provided.

Correlation between Physico-Chemical Characteristics of Particulated β-Lactoglobulin and Its Behavior at Air/Water and Oil/Water Interfaces

It is widely accepted that protein-based particles can efficiently stabilize foams and emulsions. However, it is not fully elucidated which particle properties are decisive for the stabilization of air/water and oil/water interfaces. To unravel this correlation, selected properties of nano-sized soluble β-lactoglobulin particles were changed one at a time. Therefore, particles of (1) variable size but similar zeta potential and degree of cross-linking and (2) similar size but different further properties were produced by heat treatment under a specific combination of pH value and NaCl concentration and then analyzed for their interfacial behavior as well as foaming and emulsifying properties. On the one hand, it was found that the initial phase of protein adsorption at both the air/water and the oil/water interface was mainly influenced by the zeta potential, independent of the particle size. On the other hand, foam stability as resolved from the time-dependent evolution of mean bubble area negatively correlated with disulfide cross-linking, whereas emulsion stability in terms of oil droplet flocculation showed a positive correlation with disulfide cross-linking. In addition, flocculation was more pronounced for larger particles. Concluding from this, foam and emulsion stability are not linked to the same particle properties and, thus, explanatory approaches cannot be used interchangeably.

Whey Protein Isolate Microgel Properties Tuned by Crosslinking with Organic Acids to Achieve Stabilization of Pickering Emulsions

Whey protein isolate (WPI) can be used effectively to produce food-grade particles for stabilizing Pickering emulsions. In the present study, crosslinking of WPI microgels using organic acids (tannic and citric acids) is proposed to improve their functionality in emulsions containing roasted coffee oil. It was demonstrated that crosslinking of WPI by organic acids reduces the microgels’ size from ≈1850 nm to 185 nm and increases their contact angle compared to conventional WPI microgels, achieving values as high as 60°. This led to the higher physical stability of Pickering emulsions: the higher contact angle and smaller particle size of acid-crosslinked microgels contribute to the formation of a thinner layer of particles on the oil/water (O/W) interface that is located mostly in the water phase, thus forming an effective barrier against droplet coalescence. Particularly, emulsions stabilized by tannic acid-crosslinked WPI microgels presented neither creaming nor sedimentation up to 7 days of storage. The present work demonstrates that the functionality of these crosslinked WPI microgels can be tweaked considerably, which is an asset compared to other food-grade particles that mostly need to be used as such to comply with the clean-label policy. In addition, the applications of these particles for an emulsion are much more diverse as of the starting material.

Application of Advanced Emulsion Technology in the Food Industry: A Review and Critical Evaluation

The food industry is one of the major users of emulsion technology, as many food products exist in an emulsified form, including many dressings, sauces, spreads, dips, creams, and beverages. Recently, there has been an interest in improving the healthiness, sustainability, and safety of foods in an attempt to address some of the negative effects associated with the modern food supply, such as rising chronic diseases, environmental damage, and food safety concerns. Advanced emulsion technologies can be used to address many of these concerns. In this review article, recent studies on the development and utilization of these advanced technologies are critically assessed, including nanoemulsions, high internal phase emulsions (HIPEs), Pickering emulsions, multilayer emulsions, solid lipid nanoparticles (SLNs), multiple emulsions, and emulgels. A brief description of each type of emulsion is given, then their formation and properties are described, and finally their potential applications in the food industry are presented. Special emphasis is given to the utilization of these advanced technologies for the delivery of bioactive compounds.

Structuring Pickering Emulsion Interfaces with Bilayered Coacervates of Cellulose Nanofibers and Hectorite Nanoplatelets

In this study, we present a water-in-silicone oil (W/S) Pickering emulsion system stabilized via in situ interfacial coacervation of attractive hectorite nanoplatelets (AHNPs) and bacterial cellulose nanofibrils (BCNFs). A bilayered coacervate is generated at the W/S interface by employing the controlled electrostatic interaction between the positively charged AHNPs and the negatively charged BCNFs. The W/S interface with the bilayered coacervate shows a significant increase in the interfacial modulus by 2 orders of magnitude than that with the AHNPs only. In addition, we observe that water droplets are interconnected by the BCNF bridging across the continuous phase of silicon, which is attributed to the diffusive transport phenomenon. This droplet interconnection results in the effective prevention of drop coalescence, which is confirmed via emulsion sedimentation kinetics. These results indicate that our bilayered coacervation technology has the potential of developing a promising Pickering emulsion platform that can be used in the pharmaceutical and cosmetic industries.

Impact of encapsulating probiotics with cocoa powder on the viability of probiotics during chocolate processing, storage, and in vitro gastrointestinal digestion

Chocolates can be formulated as a functional food via enrichment with probiotics. However, the added probiotics must overcome the challenges of processing and storage conditions and the harsh gastrointestinal environment. The study aimed to overcome these challenges using two different formulations of cocoa powder as alternative encapsulants along with Na-alginate (A₁ ) and Na-alginate and fructooligosaccharides (A₂ ). Seven different probiotic strains were encapsulated individually using the new formulations and viabilities of these encapsulated probiotics were assessed prior to and after they were added to chocolates. The highest achieved encapsulation efficiencies were 93.40% for formulation A₁ (with Lactobacillus casei) and 95.36% for formulation A₂ (with Lactobacillus acidophilus La5). The encapsulated probiotics with the new formulations maintained higher viability than the recommended therapeutic level (10⁷ colony forming unit [CFU]/g) for up to 180 and 120 days of storage at 4 and 25 °C, respectively. The tested encapsulants improved probiotics survival when subjected to thermal stress and maintained about 9.0 Logs CFU/g at 60 °C. Additionally, the viable numbers of probiotics in fortified chocolates showed higher than 7 Logs CFU/g after 90 days of storage at 25 °C. Both formulations exhibited significantly (P < 0.05) high survivability of probiotics (8.0 Logs CFU/g) during the in vitro gastrointestinal digestion. This study demonstrated that cocoa powder along with Na-alginate and FOS has the potential to be used as a probiotic encapsulating material, and chocolates could be an excellent carrier for the development of healthy probiotic chocolate products. PRACTICAL APPLICATION: The introduction of cocoa powder as an effective encapsulating agent to deliver probiotics could help the chocolate industry to develop healthy and attractive functional snacks for health-conscious consumers.

Pickering emulsions stabilized by luteolin micro-nano particles to improve the oxidative stability of pine nut oil

BACKGROUND

Pine oil contains a high percentage of polyunsaturated fatty acids, which make it prone to oxidation. Luteolin (LUT) micro-nano particles with antioxidant properties can be used as stabilizers to form an edible oil-in-water Pickering emulsion to improve the oxidative stability of pine nut oil.

RESULTS

Under optimal preparation conditions, the LUT micro-nano particles and pine nut oil account for about 0.44 and 90.9 g·kg^-1 of the total mass of the emulsion, respectively. The LUT particles in the suspension have a mean particle size of about 479 nm, present a sheet-like structure with a cut surface of 30-50 nm, and can reduce the surface tension of deionized water. In the optimized Pickering emulsion, the emulsion droplets are approximately spherical and have a mean diameter of about 125.6 nm and uniform distribution. The optimized Pickering emulsion droplets can remain stable for up to 2 h in an environment where the pH levels are 7-8.5, ultraviolet B radiation (UVB) irradiation, of less than 5.0 g·kg^-1 , and at a temperature of 80 °C. The stability of the emulsion in simulated digestive fluid changed minimally. In the first 7 days of the accelerated oxidation experiment, LUT micro-nano particles not only successfully protected the integrity of emulsion droplets but also fully inhibited the peroxidation of pine oil.

CONCLUSION

The strong antioxidant properties of LUT micro-nano particles, and the dense protective layer they formed, stabilized the Pickering emulsion successfully. The particles also improved the oxidation stability of pine nut oil. © 2020 Society of Chemical Industry.