Preparation and characterization of pickering emulsion stabilized by hordein-chitosan complex particles

Modification of hordein by gallic acid in ethanol-free environments: Impact of covalent and non-covalent interactions on structure, physicochemical properties and self-assembly

The objectives of this study were to modify hordein with gallic acid (GA) in alcohol-free media and to compare the impact of covalent and non-covalent binding on the properties of hordein. Covalent hordein-GA complexes (H-GA) and non-covalent hordein/GA complexes (H/GA) were distinguished by molecular weight, free sulfhydryl groups and free amino groups. Isothermal titration calorimetry (ITC) demonstrated that physical mixing induced non-covalent binding of GA to hordein via hydrogen bonding and hydrophobic interactions, with a lower binding efficiency than covalent ones. Both complexation types led to a structural shift of hordein toward disorder, while grafting of oligomeric GA and alkaline treatment resulted in lower surface hydrophobicity and higher antioxidant activity of H-GA compared to H/GA. The nanoparticles assembled from H-GA had smaller particle sizes and higher physical stability than those formed from H/GA. The results of this study may provide new insights into the modification of hordein by polyphenols.

Properties regulation and mechanism on ferritin/chitooligosaccharide dual-compartmental emulsions and its application for co-encapsulation of curcumin and quercetin bioactive compounds

Dual-compartmental emulsions, containing multiple chambers, possess great advantages in co-encapsulation of different cargoes. Herein, we reported a stable dual-compartmental emulsion by regulating the ratio of Marsupenaeus japonicus ferritin (MF) and chitooligosaccharide (COS), enabling efficient co-encapsulation of different compounds. The adsorption behavior of MF/COS complex over droplet interface varied at different ratios, thereby exerting an influence on the emulsion properties. Remarkably, emulsions stabilized by MF/COS complex at a ratio of 2:1 exhibited superior stability, as evidenced by no significant creaming or demulsification during storage or heat treatment. The mechanism is that MF/COS2:1 complex can enhance the formation of thicker interfacial layer and dense continuous phase network structure. Additionally, curcumin and quercetin can be co-encapsulated into the emulsions and their retention rates were significantly improved than those in oils, implying the potential of the resulting dual-compartmental emulsions in co-encapsulation and delivery of bioactive compounds.

Screening, characterization and mechanism of a potential stabiliser for nisin nanoliposomes with high encapsulation efficiency

The encapsulation efficiency (EE%) reflects the amount of bioactive components that can be loaded into nanoliposomes. Obtaining a suitable nanoliposome stabiliser may be the key to improving their EE%. In this study, three polyphenols were screened as stabilisers of nanoliposomes with high nisin EE%, with curcumin nanoliposomes (Cu-NLs) exhibiting the best performance (EE% = 95.94%). Characterizations of particle size, PDI and zeta potential indicate that the Cu-NLs had good uniformity and stability. TEM found that nisin accumulated at the edges of the Cu-NLs' phospholipid layer. DSC and FT-IR revealed that curcumin was involved in the formation of the phospholipid layer and altered its structure. FT-IR and molecular docking simulations indicate that the interactions between curcumin and nisin are mainly hydrogen bonding and hydrophobic. In whole milk, Cu-NLs effectively protected nisin activity. This study provides an effective strategy for improving the EE% of nanoliposomes loaded with nisin and other bacteriocins.

Ultrasonic enhancement of structural and emulsifying properties of heat-treated soy protein isolate nanoparticles to fabricate flaxseed-derived diglyceride-based pickering emulsions

Flaxseed-derived diglyceride (DAG)-based Pickering emulsions were fabricated using soy protein isolate (SPI) nanoparticles as stabilizer. The SPI nanoparticles were prepared under the combined action of heating and ultrasound treatment. The SPI nanoparticles exposed to 600 W power exhibited the smallest particle size (133.36 nm) and zeta potential (-34.77 mV). Ultrasonic treatment did not significantly impact the polypeptide chain's primary structure but induced changes in the secondary structure. The Pickering emulsions stabilized with ultrasound-treated SPI nanoparticles showed smaller particle size, lower zeta potential, and improved emulsifying properties. Notably, at 450 W power, these emulsions showed a higher solid-liquid balance, reduced mean square displacement, backscattering fluctuations, and turbiscan stability index. Besides, they displayed a more compact microstructure with smaller droplets. In conclusion, SPI subjected to heating and 450 W ultrasound power resulted in the fabrication of DAG-based Pickering emulsions with enhanced microstructure and stability.

General approaches to biopolymer-based Pickering emulsions

Pickering emulsion is a type of emulsion that uses solid particles or colloidal particles as emulsifiers rather than surfactants to adhere at oil-water interface. Pickering emulsions have gathered significant research attention recently due to their excellent stability and wide range of potential uses compared to traditional emulsions. Major advancements have been made in development of innovative Pickering emulsions using different colloidal particles by various techniques including homogenization, emulsification and ultrasonication. Use of biopolymer particles gives Pickering emulsions a more escalating possibilities. In this review paper, we seek to present a critical overview of development in food-grade particles that have been utilized to create Pickering emulsions with a focus on techniques and application of Pickering emulsions. Particularly, we have evaluated protein, lipid, polysaccharide-based particles and microalgal proteins that have emerged in recent years with respect to their potential to stabilize and add novel functionalities to Pickering emulsions. Some preparation methods of Pickering emulsions in brief, applications of Pickering emulsions are also highlighted. Encapsulation and delivery of bioactive compounds, fat substitutes, film formation and catalysis are potential applications of Pickering emulsions. Pickering double emulsions, nutraceutical and bioactive co-delivery, and preparation of porous materials are among research trends of food-grade Pickering emulsions.

Research progress on plant-based protein Pickering particles: Stabilization mechanisms, preparation methods, and application prospects in the food industry

At present, there have been many research articles reporting that plant-based protein Pickering particles from different sources are used to stabilize Pickering emulsions, but the reports of corresponding review articles are still far from sufficient. This study focuses on the research hotspots and related progress on plant-based protein Pickering particles in the past five years. First, the article describes the mechanism by which Pickering emulsions are stabilized by different types of plant-based protein Pickering particles. Then, the extraction, preparation, and modification methods of various plant-based protein Pickering particles are highlighted to provide a reference for the development of greener and more efficient plant-based protein Pickering particles. The article also introduces some of the most promising applications of Pickering emulsions stabilized by plant-based protein Pickering particles in the food field. Finally, the paper also discusses the potential applications and challenges of plant-based protein Pickering particles in the food industry.

Pickering Emulsion Stabilized by Hordein-Whey Protein Isolate Complex: Delivery System of Quercetin

As a lipophilic flavonol, quercetin has low bioavailability, which limits its application in foods. This work aimed to prepare a hordein-based system to deliver quercetin. We constructed hordein-whey isolate protein fibril (WPIF) complexes (H-Ws) by anti-solvent precipitation method at pH 2.5. The TEM results of the complexes showed that spherical-like hordein particles were wrapped in WPIF clusters to form an interconnected network structure. FTIR spectra revealed that hydrogen bonds and hydrophobic interactions were the main driving forces for the complex formation. H-W1 (the mass ratio of hordein to WPIF was 1:1) with a three-phase contact angle of 70.2° was chosen to stabilize Pickering emulsions with oil volume fractions (φ) of 40-70%. CLSM images confirmed that the oil droplets were gradually embedded in the three-dimensional network structure of H-W1 with the increase in oil volume fraction. The emulsion with φ = 70% showed a tight gel structure. Furthermore, this emulsion exhibited high encapsulation efficiency (97.8%) and a loading capacity of 0.2%, demonstrating the potential to deliver hydrophobic bioactive substances. Compared with free quercetin, the bioaccessibility of the encapsulated quercetin (35%) was significantly improved. This study effectively promoted the application of hordein-based delivery systems in the food industry.

pH-responsive Pickering emulsion containing citrus essential oil stabilized by zwitterionically charged chitin nanofibers: Physicochemical properties and antimicrobial activity

In this study, zwitterionic chitin nanofibers (Z-ChNFs) were used to prepare Pickering emulsions containing citrus essential oils (CEO) and their physicochemical properties and antimicrobial activity were investigated. Results show that as-prepared Pickering emulsions exert pH-reversible properties, pH can adjust the charge of Z-ChNFs to influence the stability of the emulsion. As the concentration of Z-ChNFs increase, the droplet size of the emulsion decreases. The high concentration of Z-ChNFs (1.5 wt%) can enhance the viscosity and promote forming nano-network structures within continuous phases, and their amphiphilic nature can strengthen the capacity for adsorption on the oil/water interface, resulting in enhanced physical stability of the encapsulated CEO emulsion. Additionally, Z-ChNFs have positive effects on the improvement of antimicrobial activity of CEO. This study provides valuable implications for the development and application of essential oils as biopreservation in the food field.

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.

Bioderived Pickering Emulsion Based on Chitosan/Trialkyl Phosphine Oxides Applied to Selective Recovery of Rare Earth Elements

A novel biobased pickering emulsion (PE) material was prepared by the encapsulation of Cyanex 923 (Cy923) into chitosan (CS) to selectively recover rare earth elements (REEs) from the aqueous phase. The preparation of PE was optimized through sequentially applying a 23 full factorial design, followed by a 33 Box-Behnken design varying the Cy923 content, CS concentration, and pH of CS. The material was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), optical microscopy, rheological, compositional, and stability measurements. The resultant material was evaluated in the removal of yttrium by pH influence, nitrate concentration, kinetics, equilibrium isotherms, reusability, and a comparison with liquid-liquid (L-L) extraction and tested in a real scenario to extract Y from a fluorescent lamp powder waste. In addition, the selectivity of PE for REE was investigated with Y/Ca, Gd/Ca, and La/Ni systems. PE extracts REE at 1 ≤ pH ≤ 5 at nitrate concentrations up to 2 mol/L. The kinetics and equilibrium studies showed reaction times <5 min and a maximum sorption capacity of 89.98 mg/g. Compared with L-L extraction, PE consumed 48% less Cy923 without using organic diluents. PE showed a remarkable selectivity for REE in the systems evaluated, showing separation factors of 22.62, 9.35, and 504.64 for the blends Y/Ca, Gd/Ca/Mg, and La/Ni, respectively. PE showed excellent selectivity extracting Y from a real aqueous liquor from the fluorescent lamp powder. PE demonstrates to be an effective and sustainable alternative for REE recovering due to its excellent efficiency in harsh conditions, favorable green chemistry metrics, and use of a biopolymer material in its composition avoiding the use of organic solvents used in L-L extraction.

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.

Investigation and Characterization of Pickering Emulsion Stabilized by Alkali-Treated Zein (AZ)/Sodium Alginate (SA) Composite Particles

Pickering emulsions stabilized by food-grade colloidal particles have attracted increasing attention in recent years due to their "surfactant-free" nature. In this study, the alkali-treated zein (AZ) was prepared via restricted alkali deamidation and then combined with sodium alginate (SA) in different ratios to obtain AZ/SA composite particles (ZS), which were used to stabilize Pickering emulsion. The degree of deamidation (DD) and degree of hydrolysis (DH) of AZ were 12.74% and 6.58% respectively, indicating the deamidation occurred mainly in glutamine on the side chain of the protein. After the treatment with alkali, AZ particle size decreased significantly. Moreover, the particle size of ZS with different ratios was all less than 80 nm. when the AZ/SA ratio was 2:1(Z2S1) and 3:1(Z3S1), the three-phase contact angle (θ_o/w) were close to 90°, which was favorable for stabilizing the Pickering emulsion. Furthermore, at a high oil phase fraction (75%), Z3S1-stabilized Pickering emulsions showed the best long-term storage stability within 60 days. Confocal laser scanning microscope (CLSM) observations showed that the water-oil interface was wrapped by a dense layer of Z3S1 particles with non-agglomeration between independent oil droplets. At constant particle concentration, the apparent viscosity of the Pickering emulsions stabilized by Z3S1 gradually decreased with increasing oil phase fraction, and the oil-droplet size and the Turbiscan stability index (TSI) also gradually decreased, exhibiting solid-like behavior. This study provides new ideas for the fabrication of food-grade Pickering emulsions and will extend the future applications of zein-based Pickering emulsions as bioactive ingredient delivery systems.

Recent developments in improving the emulsifying properties of chitosan

Chitosan is one of the valuable products obtained from crustacean waste. The unique characteristics of chitosan (antimicrobial, antioxidant, anticancer, and anti-inflammatory) have increased its application in various sectors. Besides unique biological properties, chitosan or chitosan-based compounds can stabilize emulsions. Nevertheless, studies have shown that chitosan cannot be used as an efficient stabilizer because of its high hydrophilicity. Hence, this review aims to provide an overview of recent studies dealing with improving the emulsifying properties of chitosan. In general, two different approaches have been reported to improve the emulsifying properties of chitosan. The first approach tries to improve the stabilization property of chitosan by modifying its structure. The second one uses compounds such as polysaccharides, proteins, surfactants, essential oils, and polyphenols with more wettability and emulsifying properties than chitosan's particles in combination with chitosan to create complex particles. The tendency to use chitosan-based particles to stabilize Pickering emulsions has recently increased. For this reason, more studies have been conducted in recent years to improve the stabilizing properties of chitosan-based particles, especially using the electrostatic interaction method. In the electrostatic interaction method, numerous research has been conducted on using proteins and polysaccharides to increase the stabilizing property of chitosan.

Chestnut Starch Nanocrystal Combined with Macadamia Protein Isolate to Stabilize Pickering Emulsions with Different Oils

This study investigated the formation and molecular interaction mechanism of chestnut starch nanocrystal (SNC)/macadamia protein isolate (MPI) complexes and their application in edible oil-in-water Pickering emulsion (PE). SNC/MPI complexes were characterized by scanning electron microscopy and particle size analyzer. The PEs stabilized by SNC/MPI complexes were characterized by confocal laser scanning microscopy and rheological measurement. The results showed that hydrogen bonds between the two particles significantly affected the secondary structure and assembly of SNC/MPI complexes at the oil/water interface. The optimal mass ratio of SNC to MPI in the complexes with the best stability was determined as 20:1. The formation of edible oil-in-water PEs stabilized by SNC/MPI complexes significantly improved the oxidative and storage stability of different edible oils (olive oil, walnut oil, edible tea oil, and macadamia oil). These different edible oil-in-water PEs stabilized by SNC/MPI could be used as effective carriers of quercetin with their loading rates higher than 93%.

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.

Enzymatically modified quinoa starch-based Pickering emulsion: Effect of enzymolysis and emulsifying conditions

Both the effects of enzymolysis condition on the microstructures and emulsifying property of enzymatic modified quinoa starch (EMQS) and the effects of emulsion formulation on the EMQS based emulsions were investigated. The emulsifying capacity (EC) and stability (ES) of EMQS were positive correlated with enzyme amount (0-2.4 % w/w_starch). The particle sizes of EMQS decreased and its hydrophobicity increased with increasing enzyme amount (0-2.4 % w/w_starch), which were the main reasons for the increasing emulsifying performance of EMQS. With the increasing starch concentration, the EC of the EMQS increased, the oil droplet size of the emulsion decreased. With the oil/water ratios ranging from 1:9 to 6:4, the emulsification index (EI) and oil droplet size of the emulsion increased. EMQS based emulsion had a relatively good stability in the pH range of 2-10. This study lays the foundation for the application of EMQS as a stable clean-label Pickering emulsifier.

Study on stability of grape seed oil/rice hydrolyzed protein emulsion

In this study, the stability mechanism of grape seed oil/rice hydrolyzed protein emulsion was studied. The grape seed oil (10% v/v) and rice hydrolyzed protein (2% w/v) were homogenized under high pressure to prepare the emulsion. It was observed by CLSM and Multiple light scatterometer that the emulsion had long-term storage stability, and the average particle size of droplets was 0.984–1.363 µm. ζ-potential ranged from −37.733 mV to −25.633 mV. It is found that the emulsion has strong resistance to temperature, ions and other environmental factors from the macroscopic and microscopic structure, and no emulsion stratification phenomenon occurs. The composite emulsion can be used in the field of food industry and fine chemical industry, which can provide nutrition and functionality of products, its research has certain value and has a wide space for development.

Isolation of B-constituent through selective complex coacervation of hordein with ι-carrageenan

The complex behavior of the crude hordein with ι-carrageenan (Car) as a function of pH (11.0-3.0) and Hordein/Car mass ratios (20:1-1:1, w/w) was studied through zeta potential analysis, turbidimetric titration and SDS-PAGE. By preferential binding with Car, B-hordein was isolated from the crude hordein at pH_max (6.2) and Hordein/Car mass ratio of 15:1, which was further confirmed by LC-MS/MS analysis. The results of zeta potential and size of separated B-hordein and C-hordein suggested that the difference in charge density was the main driving force of selective complexation between hordein and Car. Simultaneously, Fourier transform infrared spectroscopy also confirmed the existence of strong electrostatic interaction between B-hordein and Car. Additionally, the more ordered secondary structure of B-hordein at pH_max might be beneficial to its preferential binding with Car. This study further promotes the application of B-hordein in food industry.

Recent Advances on Pickering Emulsions Stabilized by Diverse Edible Particles: Stability Mechanism and Applications

Pickering emulsions, which are stabilized by particles, have gained considerable attention recently because of their extreme stability and functionality. A food-grade particle is preferred by the food or pharmaceutical industries because of their noteworthy natural benefits (renewable resources, ease of preparation, excellent biocompatibility, and unique interfacial properties). Different edible particles are reported by recent publications with distinct shapes resulting from the inherent properties of raw materials and fabrication methods. Furthermore, they possess distinct interfacial properties and functionalities. Therefore, this review provides a comprehensive overview of the recent advances in the stabilization of Pickering emulsions using diverse food-grade particles, as well as their possible applications in the food industry.

Fabrication and characterization of superior stable Pickering emulsions stabilized by propylene glycol alginate gliadin nanoparticles

Gliadin, a kind of amphiphilic protein from wheat, has been widely used for stabilizing Pickering emulsions, which is easy to form colloidal particles. Herein, gliadin/propylene glycol alginate (PGA) colloidal particles (GPPs) with different gliadin/PGA ratios were developed and used as emulsifiers to prepare Pickering emulsions with an internal phase of 80% (v/v). The addition of PGA made the GPPs a tree-fruit-like morphology, increasing the particle size and changing the zeta-potential. Hydrogen bond and electrostatic interaction are the major forces between gliadin and PGA. The wettability of GPPs was improved significantly in the presence of PGA. The oil-water contact angle reached 89.5° when the gliadin/PGA ratio was 1 : 1. The emulsion could be maintained at room temperature for 6 months when the oil phase ratio (Φ) was 70%. The high stability of the Pickering emulsion could be attributed to the thin film formed by GPPs on the surface of oil droplets. The improved resistance of algal oil in emulsions against oxidation was proved as the induction time increased six times. In addition, the porous material prepared using GPPs-stabilized emulsion as the template displayed an oil absorption ability of 106.41 g g^-1 and heavy metal adsorption ability of 202.71 mg g^-1. Such performance implies that GPPs are highly efficient food-grade Pickering emulsifiers that may be applied in various fields.

Pickering emulsions stabilized by pea protein isolate-chitosan nanoparticles: fabrication, characterization and delivery EPA for digestion in vitro and in vivo

The work aimed to prepare pea protein isolate-chitosan (PPI-CS) nanoparticles, fabricate PPI-CS nanoparticles stabilized Pickering emulsions (PPI-CS Pickering emulsions) and deliver EPA for digestion in vitro and in vivo. The nanoparticles were characterized by scanning electron microscopy (SEM), and PPI-CS Pickering emulsions were characterized by physicochemical and rheological properties. The results showed that the size of PPI-CS nanoparticles was 194.22 ± 0.45 nm. Rheological measurement showed that the PPI-CS Pickering emulsions possessed a gel-like network. EPA encapsulated Pickering emulsions (EPA-PE, φ = 0.6) exhibited a high retention rate (93%) during storage and performed a lower release rate compared with EPA-PE (φ = 0.4) in vitro digestion. The area under the curve of EPA concentration of EPA-PE group and EPA-emulsions (EPA-Em) group was 1.71 and 1.48, respectively. It demonstrated that PPI-CS Pickering emulsions provided the possibility to deliver EPA for digestive absorption.

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.