Food-grade Pickering Emulsions Research Articles

Construction and characteristics of EGCG-porcine serum albumin pickering emulsion: Based on noncovalent interactions mechanism

Pickering emulsion prepared by the interaction between polyphenols and protein can improve the stability of protein-based emulsion. The purpose of this study was to explore the complex formation mechanism of epigallocatechin gallate (EGCG)-porcine serum albumin (PSA) complex and the preparation of food-grade Pickering emulsion. By the UV and fluorescence spectral analysis, it was found that EGCG has an obvious fluorescence quenching effect on PSA, mainly static quenching. The results of synchronous, three-dimensional fluorescence and FT-IR spectroscopy showed that the hydrophobic microenvironment of aromatic amino acids and the secondary structure of PSA changed after EGCG was added. The results of molecular docking examined that EGCG and PSA form more stable complexes due to hydrogen bonds, and the binding energy was −4.43 kcal /mol. Compared with the PSA emulsion, the successfully prepared EGCG-PSA Pickering emulsion had smaller droplets and no obvious color in CLMS. The Pickering emulsion of EGCG-PSA had strong emulsification and high viscosity, which belonged to pseudoplastic non-Newtonian fluid. In addition, the free fatty acids release rate of EGCG-PSA Pickering emulsion was decreased by 9.9 %. The antioxidant performance of the EGCG-PSA Pickering emulsion was improved, and the DPPH radical scavenging rate and the ABTS+ radical scavenging rate reached the highest, which were 93.72 % and 57.16 % respectively. This study provides important insights into the interaction between EGCG and PSA, and a reference for the development of polyphenol-protein complex Pickering emulsion in food, medicine, cosmetics, and other fields.

Characteristics of sweet potato starch particles modified by various methods for use in food-grade Pickering emulsion

The objective of the current work was to formulate Pickering emulsions prepared solely of sweet potato starch that were renewable and surfactant-free. Native starch has a low capacity for emulsification, for this reason, three different modification techniques including anti-solvent precipitation, esterification with octenyl succinic anhydride (OSA), and hydrothermal treatment were applied to modify native sweet potato starch particles (NSPSP). The outcomes demonstrated that the characteristics of the particles, such as size, wettability, surface morphology, crystallinity, thermal behavior, and interfacial tension, were significantly impacted by modification. The amylose content and roughness of NSPSP were reduced by applying OSA, and OSA-modified samples had the highest contact angle and crystalline region. Conversely, ethanol-induced starch granules showed increased amorphous area, higher surface roughness, and agglomeration. From an interfacial perspective, esterification of starch with OSA could decrease the interfacial tension, whereas the anti-solvent approach caused an increase in this parameter. Droplet size, surface charge, microstructure, and emulsification index were used to describe O/W Pickering emulsions stabilized by native and modified particles. This investigation suggested that, in contrast to the other two techniques, modifying NSPSP with OSA had a favorable effect on the emulsifying capacity of the resulting Pickering emulsion. The findings suggested that modified NSPSP could be a promising candidate to stabilize Pickering emulsion with demanding characteristics, which could be applied for carrying the bioactive compounds.

Preparation and characterization of a new food-grade Pickering emulsion stabilized by mulberry-leaf protein nanoparticles.

Food-grade Pickering particles, particularly plant proteins, have attracted significant interest due to their bio-based nature, environmental friendliness, and edibility. Mulberry-leaf protein (MLP) is a high-quality protein with rich nutritional value and important functional properties. It has special amphoteric and emulsifying characteristics, making it valuable for use in Pickering emulsions. This study aimed to investigate the feasibility of using MLP nanoparticles as solid particles to stabilize Pickering emulsions. The particle size of MLP nanoparticles was less than 300 nm under neutral and alkaline conditions. At pH 9, the zeta potential value reached -34.3 mV, indicating the electrostatic stability of the particles. As ion concentration increased, the particle size of MLP nanoparticles increased, and the zeta potential decreased. Throughout the storage process, no obvious aggregation or precipitation was observed in the dispersion of MLP nanoparticles, indicating strong stability. The particle size of the Pickering emulsion decreased with the increase in protein concentration. When the protein concentration was low, the particles on the oil-water interface became sparse, resulting in poor stability of the prepared emulsion and making it susceptible to aggregation and thus larger particle sizes. Increasing the oil-phase ratio to 70% (v/v) promotes the formation of Pickering emulsions, which exhibit exceptional stability when MLP nanoparticles are fixed at a concentration of 20 mg mL-1. The overall findings indicated that MLP nanoparticles have potential as food-grade materials for Pickering emulsions, marking a novel application of these nanoparticles in the food industry. © 2024 Society of Chemical Industry.

Enhancing the Retention and Oxidative Stability of Volatile Flavors: A Novel Approach Utilizing O/W Pickering Emulsions Based on Agri-Food Byproducts and Spray-Drying.

Spray-drying is a commonly used method for producing powdered flavors, but the high temperatures involved often result in the loss of volatile molecules. To address this issue, our study focused on a novel approach: developing O/W Pickering emulsions with agri-food byproducts to encapsulate and protect D-limonene during spray-drying and storage. Emulsions formulated with lupin hull, lupin-byproduct (a water-insoluble protein-fiber byproduct derived from the production of lupin protein isolate), and camelina press-cake were subjected to spray-drying at 160 °C. The results revealed that these emulsions exhibited good stability against creaming. The characteristics of the dry emulsions (powders) were influenced by the concentration of byproducts. Quantitative analysis revealed that Pickering emulsions enhanced the retention of D-limonene during spray-drying, with the highest retention achieved using 3% lupin hull and 1% camelina press-cake. Notably, lupin-stabilized emulsions yielded powders with enhanced oxidative stability compared to those stabilized with camelina press-cake. Our findings highlight the potential of food-grade Pickering emulsions to improve the stability of volatile flavors during both processing and storage.

Cellulose nanofibrils-stabilized food-grade Pickering emulsions: Clarifying surface charge's contribution and advancing stabilization mechanism understanding

Pickering emulsions stabilized by cellulose nanofibrils (CN) have sparked significant attention, however the fundamental mechanisms underpinning the stabilization process remain insufficiently elucidated. Focusing on an academic debate of surface charge's contribution to stabilization, this study first explored how the varying carboxyl group contents of TEMPO-oxidized CN (TCNs) impacted Pickering emulsions' formation and stability. TCNs with 662 μmol/g carboxyl groups exhibited distinctive attributes, including larger particle sizes (322 nm in length), improved thermal stability (maximum decomposition temperature of 317 °C), and increased viscosity (1.57 Paִִ⋅s) compared to their counterparts with 963–1011 μmol/g charge density. Notably, the former one, with a larger three-phase contact angle (51.5°), higher interfacial tension, and greater detachment energy (21.69 × 10−18 J), resulted in a homogeneous dispersion of spherical oil droplets and super-stable Pickering emulsions with a consistent emulsifying index of 100% over 30 days. These findings clearly clarified that TCNs with a lower charge density exhibit superior emulsifying properties. In addition, for the first time, a distinct oil droplet-decorated fibrillar structure was observed, probably suggesting that TCNs might be able to serve as anchoring matrixes to guide the distribution of oil droplets. These structures seemed to impeded the migration and accumulation of the oil droplets, consequently enhancing the stability of the resulting Pickering emulsions. To sum, this study clearly elucidated the role of surface charge in stabilizing cellulose-based Pickering emulsions and proposed a new model to expound the cellulose-oil interaction mechanisms, thus providing new theoretical and practical insights on utilization of CN as highly effective emulsifier for super-stable food-grade Pickering emulsions.

Novel Pickering emulsion stabilized by glycated casein embedding curcumin: Stability, bioaccessibility and antioxidant properties

To overcome the barrier of poor stability and low bioaccessibility of curcumin, a novel food-grade Pickering emulsion was constructed using casein and oligochitosan by transglutaminase (TGase)-type glycation method to deliver curcumin. The effect of glycation on the emulsion's physicochemical properties, stability, antioxidant properties and in vitro digestion behavior was assessed with casein and crosslinked casein as a control. The results suggested that the optimal preparation condition was achieved at an oil/water ratio of 1:25 and a protein concentration of 5 %. It was noted that the Pickering emulsion with glycated casein had the highest curcumin encapsulation efficiency (92.93 %) among those stabilized with unmodified and modified casein and exhibited excellent stability under different environmental stresses. In vitro digestion results demonstrated that glycated casein emulsion significantly delayed the release of curcumin and increased the bioaccessibility of curcumin. Moreover, the resulting curcumin-loaded Pickering emulsions exhibited significant antioxidant activity. This study provides new insights into the glycated casein via TGase-type for preserving hydrophobic compounds in Pickering emulsions, thus improving the application of these nutrients in commercial products.

Pickering emulsion with high freeze-thaw stability stabilized by xanthan gum/lysozyme nanoparticles and konjac glucomannan

In this study, freeze-thaw cycle experiments were conducted on food-grade Pickering emulsions co-stabilized with konjac glucomannan (KGM) and xanthan gum/lysozyme nanoparticles (XG/Ly NPs). The rheological properties, particle size, flocculation degree (FD), coalescence degree (CD), centrifugal stability, Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and microstructure of Pickering emulsion stabilized by KGM before and after freeze-thaw were characterized. It was found that as the concentration of KGM increased, the flocculation degree (FD) and coalescence degree (CD) of the emulsion decreased after the freeze-thaw cycle compared to the control sample, and the microscopic images showed that the droplets became smaller and less affected by the freeze-thaw cycles. The rheological and water-holding properties also confirmed that the KGM-added emulsions still had a strong gel network structure and prevented the separation of the continuous and dispersed phases of the droplets after freezing and thawing. Freeze-thaw treatments had a negative effect on the stable emulsion of XG/Ly NPs, while the addition of KGM improved the freeze-thaw stability of the emulsion, which provided a theoretical basis for the development of emulsion products with high freeze-thaw stability.

Structural modification of whey protein nanofibrils by a multiround induction pathway for enhancing the stability of Pickering emulsions

In this study, a new fibrillation method, i.e., a multiround induction pathway, was proposed to modify the highly rigid structure of conventional whey protein nanofibrils and enhance the stability of Pickering emulsions. In contrast to the conventional self-assembly pathway, in which nanofibrils are formed by aggregation of polypeptides or monomers, the multiround induction pathway involves the use of multiple rounds of homologous seeds to induce whey protein nanofibril formation. The structure of nanofibrils formed by multiround induction was considerably different from that of conventionally self-assembled nanofibrils, with a greater or equal number of nanofibrils formed. Over 6 rounds of induction, the intersheet distance within the cross-β-sheet motifs of the nanofibrils increased (from 10.01 Å to 10.70 Å), and the intersheet stacking structure gradually became looser, consequently displaying a thicker morphology with greater height and periodicity. Compared to conventionally self-assembled nanofibrils, nanofibrils with this characteristic structure exhibited 4.04 times higher interfacial adsorption, an 83.24% lower flocculation index, and 61.29% higher emulsion stability. Differences in the emulsification properties of nanofibrils were attributed to multiround induction, which changed the nanofibril structure compared to conventional self-assembly. Some hydrophobic peptides at the β-sheet and α-helix positions were not involved in the construction of cross-β-sheet motifs, which made the nanofibrils more flexible and hydrophobic. These findings suggested that nanofibrils prepared via the multiround induction pathway had unique properties that might be significant for the fabrication of food-grade Pickering emulsions with excellent stability.

Recombinant microgels utilized to formulate green Pickering emulsions

The fabrication of a stable food-grade Pickering emulsion (PEs) system has been challenging because of difficulties in ensuring the safety of auxiliary reagents and the compatibility of the materials. In this study, inspired by our previous experiments, we devised recombinant microgels (RMs) with a compact structure by freeze–thaw cycles (FTCs) method, which was used to fabricate a green food-grade PE system. The application of FTCs demonstrated an enhancement of RMs in the crystallinity, surface wettability, and textural properties. Specifically, RMs subjected to 3 FTCs had a compact cube structure (0.6–1.1 μm), near neutral surface wettability (89.95°), and an amorphous crystallinity (55.93%), which may be attributed to the decrease of free water content and the formation of hydrogen bonds. A concentration of 0.5% RMs was used to stabilize PEs, which showed a uniform microscopic distribution and a particle size of 13.87 μm. It was found that when the concentration of the external phase exceeded 0.5% stable oil-in-water emulsions formed. Otherwise, multiple emulsions formed. This study underscores the viability of using RMs to construct green food-grade PE systems.

Physicochemical properties of Pickering emulsion fabricated with polysaccharides/pea protein isolate complex and its application in plant-based patty

Incorporation of structured liquid oil within plant-based patties can be achieved through the utilization of food-grade Pickering emulsion (PE). Therefore, the aim of this study was to evaluate the quality characteristics of PE and its application in plant-based patty. The PEs were formulated using sunflower oil (SO), polysaccharides and protein, and the specific ratios employed were as following: methylcellulose (MC) 2 % only (MP0); MC 1.5 % + pea protein isolate (PPI) 0.5 % (MP1); MC 1 % + PPI 1 % (MP2); xanthan gum (XG) 2 % only (XP0); XG 1.5 % + PPI 0.5 % (XP1); XG 1 % + PPI 1 % (XP2). MP0 and MP1 were unstable as PEs, whereas MP2 and XP groups (XP0, XP1, and XP2) exhibited stability as a PE. In addition, MP2 and all XP groups showed increased oil binding capacity, hydrophobic interaction, thermal stability, crystallization, rheological properties, and oxidative stability, compared to MP0 and MP1. In PE-applied plant-based patties, MP2 and all XP groups had significantly lower cooking loss and higher emulsion stability than SO. Particularly, MP2-employed plant-based patties exhibited significantly improved textural and sensory properties. Therefore, our data suggest that PEs with methylcellulose and pea protein isolate could be an effective replacement of plant oil in plant-based meat analogs.

Interfacial behavior and micro-rheological performance of Pickering emulsions co-stabilized by β-cyclodextrin and xanthan gum

Pickering emulsions have higher physical and energy barriers than typical emulsions, preventing emulsion droplets aggregation more effectively. The poor surface activity of β-cyclodextrin (CD) has limited its application in Pickering emulsions, and in order to improve the emulsifying performance of CD, in this paper, Pickering emulsions for usage in the food pathway were prepared using the xanthan gum (XG)/CD complex with different mass ratios. The CD was mixed with XG at a same concentration to form XG1/CD1 mixture, which possessed the highest absolute value of ζ-potential (54.5 mV), optimal wettability (76.9°) and interfacial behavior (like minimum interfacial tension, highest interfacial pressure, diffusion rate, penetration rate and rearrangement rate), could be firmly adsorbed at the oil-water interface and supply electrostatic repulsion and steric hindrance against the aggregation of emulsion droplets. Subsequently, the micro-rheological analysis indicated that XG1/CD1-stabilized emulsion had the highest MVI value (0.79 nm−2·s at 3600 s), suggesting it may be more dominant during long-term stability. Furthermore, the correlation between interfacial behavior of the XG/CD complex and the emulsion’ long-term stability index was revealed by establishing a Pearson correlation analysis model, and the results demonstrated that the long-term stability of the Pickering emulsions can be predicted by the interfacial behavior of XG/CD complex, which had a significant correlation (p ≤ 0.05). Our findings not only present a novel application for CD and XG in food, but also a new strategy for creating food-grade Pickering emulsion.

Chitosan-based food-grade Pickering emulsion loading with Rosa roxburghii extract against precancerous lesions of gastric carcinoma

Precancerous lesions of gastric carcinoma (PLGC) are the most important stage in the development of gastric cancer, accompanied by significant oxidative stress and inflammatory response. Rosa roxburghii extract (RRE) has unique advantages in anti-PLGC due to its multi-component, high antioxidant and anti-inflammatory activities. However, the astringency and instability of RRE in the digestive tract seriously hinder its clinical application. Herein, we report a chitosan-based food-grade Pickering emulsion (PE) for loading RRE to block unpleasant taste, improve stability, and promote the entry of RRE into gastric epithelial cells through the gastric adhesion of chitosan, thereby enhancing preventive and therapeutic effects against PLGC. This Pickering emulsion is constructed as a water-in-oil (W/O) emulsion stabilized by the food-grade nanoparticles composed of soybean protein isolate (SPI) and chitosan (CS) through electrostatic interaction (defined as RRE@PE). The experimental results showed that RRE@PE performed better efficacy against PLGC than RRE by scavenging or inhibiting reactive oxygen species generation and reducing inflammatory cytokines. This Pickering emulsion enhances the application potential of RRE and is expected to be used for the treatment of clinical patients with PLGC.

Phycocyanin/lysozyme nanocomplexes to stabilize Pickering emulsions for fucoxanthin encapsulation

Food-grade Pickering emulsions with plant proteins have attracted increasing interest in recent years. In this work, we report a type of phycocyanin (PC) electrostatic nanocomplex fabricated following a complexation between PC and lysozyme (Lys). The aim was to investigate toward investigating the performance of phycocyanin-Lysozyme (PC-Lys) nanocomplexes in stabilizing Pickering emulsions and protecting fucoxanthin (FX) from degradation. The properties of the PC-Lys nanocomplexes were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and three-phase contact angle. Using PC-Lys nanocomplexes as emulsifiers, Pickering emulsions were successfully prepared. Pickering emulsions stabilized by PC-Lys nanocomplexes generated a tight three-dimensional network structure, which increased the memory modulus and viscoelasticity of the emulsion. Furthermore, the produced Pickering emulsions considerably increased the chemical stability and bioavailability of FX. Overall, our study showed that PC-Lys nanocomplexes have the potential for use in Pickering emulsion construction with enhanced protective effects on loaded lipophilic ingredients.

Development and Characterization of Pickering Emulsion Stabilized by Walnut Protein Isolate Nanoparticles.

This study was conducted to prepare walnut protein isolate nanoparticles (nano-WalPI) by pH-cycling, combined with the ultrasound method, to investigate the impact of various nano-WalPI concentrations (0.5~2.5%) and oil volume fractions (20~70%) on the stability of Pickering emulsion, and to improve the comprehensive utilization of walnut residue. The nano-WalPI was uniform in size (average size of 108 nm) with good emulsification properties (emulsifying activity index and stability index of 32.79 m2/g and 1423.94 min, respectively), and it could form a stable O/W-type Pickering emulsion. When the nano-WalPI concentration was 2.0% and the oil volume fraction was 60%, the best stability of Pickering emulsions was achieved with an average size of 3.33 μm, and an elastic weak gel network structure with good thermal stability and storage stability was formed. In addition, the emulsion creaming index value of the Pickering emulsion was 4.67% after 15 days of storage. This study provides unique ideas and a practical framework for the development and application of stabilizers for food-grade Pickering emulsions.

Low oil Pickering emulsion gels stabilized by bacterial cellulose nanofiber/soybean protein isolate: An excellent fat replacer for ice cream

Food-grade Pickering emulsion gels with different oil phase fractions stabilized by Bacterial cellulose nanofibers/Soy protein isolate complex colloidal particles were prepared by one-step method. The properties of Pickering emulsion gels with different oil phase fractions (5 %, 10 %, 20 %, 40 %, 60 %, 75 %, v/v) and their applications in ice cream were investigated in the present study. The microstructural results showed that Pickering emulsion gels with the low oil phase fractions (5 %–20 %) were an emulsion droplet-filled gel, where the oil droplets were embedded in the network structure of cross-linked polymer, while Pickering emulsion gels with higher oil phase fractions (40 %–75 %) were an emulsion droplet-aggregated gel, which formed a network structure by flocculated oil droplets. The rheology result showed that the low oil Pickering emulsion gels had the same excellent performance as the high oil Pickering emulsion gels. Furthermore, the low oil Pickering emulsion gels showed good environmental stability under harsh conditions. Consequently, Pickering emulsion gels with 5 % oil phase fraction were used as fat replacers in ice cream and ice cream with different fat replacement rates (30 %, 60 % and 90 %, w/w) was prepared in this work. The results showed the appearance and texture of the ice cream with low oil Pickering emulsion gels as fat replacers was similar to that of the ice cream with no fat replacers, and the melting rate of the ice cream with low oil Pickering emulsion gels as fat replacers showed the lowest value of 21.08 % during the 45 min of melting experiment, as the fat replacer rate in the ice cream reached to 90 %. Therefore, this study demonstrated that low oil Pickering emulsion gels were excellent fat replacers and had great potential application in low calorie food production.

Pickering Emulsion Stabilized by β-Cyclodextrin and Cinnamaldehyde/β-Cyclodextrin Composite.

A Pickering emulsion was prepared using β-cyclodextrin (β-CD) and a cinnamaldehyde (CA)/β-CD composite as emulsifiers and corn oil, camellia oil, lard oil, and fish oil as oil phases. It was confirmed that Pickering emulsions prepared with β-CD and CA/β-CD had good storage stability. The rheological experiments showed that all emulsions had G' values higher than G″, thus confirming their gel properties. The results of temperature scanning rheology experiments revealed that the Pickering emulsion prepared with β-CD and CA/β-CD composites had high stability, in the range of 20-65 °C. The chewing properties of Pickering emulsions prepared by β-CD and corn oil, camellia oil, lard, and herring oil were 8.02 ± 0.24 N, 7.94 ± 0.16 N, 36.41 ± 1.25 N, and 5.17 ± 0.13 N, respectively. The chewing properties of Pickering emulsions made with the CA/β-CD composite and corn oil, camellia oil, lard, and herring oil were 2.51 ± 0.05 N, 2.56 ± 0.05 N, 22.67 ± 1.70 N, 3.83 ± 0.29 N, respectively. The texture properties confirmed that the CA/β-CD-composite-stabilized-emulsion had superior palatability. After 28 days at 50 °C, malondialdehyde (MDA) was detected in the emulsion. Compared with the β-CD and CA + β-CD emulsion, the CA/β-CD composite emulsion had the lowest content of MDA (182.23 ± 8.93 nmol/kg). The in vitro digestion results showed that the free fatty acid (FFA) release rates of the CA/β-CD composite emulsion (87.49 ± 3.40%) were higher than those of the β-CD emulsion (74.32 ± 2.11%). This strategy provides ideas for expanding the application range of emulsifier particles and developing food-grade Pickering emulsions with antioxidant capacity.

Construction and characterization of Pickering emulsions stabilized by soy protein hydrolysate microgel particles and quercetin-loaded performance in vitro digestion

Food-grade Pickering emulsions stabilized by protein microgel particles have received increasing attentions owing to their potential applications in the food industry. Herein, soy protein hydrolysate microgel particles (SPHMs) produced at various pH (3, 5, 7, and 9) with and without ultrasonication were used to stabilize Pickering emulsions. Compared with those prepared using ultrasonication at pH 3–7, SPHMs prepared using ultrasonication at pH 9 showed excellent amphiphility at the oil–water interface and a superior ability to reduce interfacial tension. The Pickering emulsion stabilized by the latter SPHMs displayed a small particle size and a high net charge on the droplet surface, formed a dense honeycomb network interfacial layer with high viscoelasticity and adsorbed protein content, and experienced no visually detectable creaming during storage for 21 days, i.e., exhibited optimum colloidal stability. Furthermore, the above emulsion featured a quercetin encapsulation efficiency of 89.45 % and was capable of sustainable release, achieving a low free fatty acid release efficiency of 61 % and a relatively high quercetin bioaccessibility of 65 % in in vitro simulated digestion experiments. Thus, this work inspires the use of SPHMs in emulsion-based functional foods.

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 (θo/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.

Pickering emulsion stabilized by casein-caffeic acid covalent nanoparticles to enhance the bioavailability of curcumin in vitro and in vivo.

In recent years, the design of food-grade Pickering emulsion delivery systems has become an effective strategy for improving the low bioavailability of bioactive substances. Protein-based Pickering emulsions have received extensive attention because of a high biocompatibility and loading capacity. The bioavailability of active substances is mainly evaluated by simulating in vitro gastrointestinal digestion. As a model organism for antioxidation and anti-aging, Caenorhabditis elegans can provide additional biological information for the in vivo utilization of active substances. After the introduction of caffeic acid, the average particle size and Zeta potential of the casein-caffeic acid covalent complex nanoparticles (CCP) were 171.11 nm and - 37.73 mV, respectively. The three-phase contact angle was also increased to 89.8°. By using CCP to stabilize Pickering emulsion (CCE), the retention quantity of the embedded curcumin increased by 2.19-fold after 28 days. In the simulated gastric digestion, curcumin degradation in CCE was reduced by 61.84%, released slowly in the intestinal environment, and the final bioaccessibility was increased by 1.90-fold. In C. elegans, CCE significantly reduced ROS accumulation, increased SOD activity by 2.01-fold and CAT activity by 2.30-fold, decreased MDA content by 36.76%, prolonging the lifespan of nematodes by 13.33% under H2 O2 stimulation and improving bioavailability in vivo. The results indictae that CCP-stabilized Pickering emulsion can efficiently implement the physiological activities of bioactive compounds in vitro digestion and C. elegans, and thus it can be regarded as a reliable delivery system for food and medicine. © 2023 Society of Chemical Industry.

Characterization of bacterial cellulose nanofibers/soy protein isolate complex particles for Pickering emulsion gels: The effect of protein structure changes induced by pH

In this work, the influence of soy protein isolated at different pH values (1–9) on the self-assembly behaviors of bacterial cellulose nanofibers/soy protein isolate (BCNs/SPI) colloidal particles via anti-solvent precipitation were investigated. The results showed that the formation of BCNs/SPI at pH values of 1–5 was mainly driven by electrostatic interaction, while the formation of those at pH values of 5–9 was driven by weak molecular interactions including hydrogen bonding and steric-hindrance effect. The FTIR demonstrated that the conformation of protein involved a transition from order to disorder at the level of secondary structure as pH values were away from the isoelectric point. The fluorescence spectroscopy and UV–vis adsorption spectroscopy indicated that hydrophobic region of SPI at pH value of 5 displayed more exposed as compared with that at pH values away from the isoelectric point. The changes in structure conformation of SPI induced by pH values led to the changes in properties of the BCNs/SPI colloidal particles including particle size, microstructure, crystallinity, hydrophily, thermal stability, and rheological properties. Furthermore, the structures of BCNs/SPI colloidal particles at different pH values significantly affected the stability of Pickering emulsion gels stabilized by the corresponding complex colloidal particles. This study provided a theoretical basis for the design of food-grade Pickering emulsion gels stabilized by BCNs/SPI complex colloidal particles.