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Heteroprotein complex coacervate (HPCC) is a liquid-like protein concentrate produced by liquid-liquid phase separation. We revealed the protein dynamic exchange and thermodynamic mechanism of β-conglycinin/lysozyme coacervate, and clarified the effect of HPCC on protein structure and activity. β-conglycinin and lysozyme assembled into coacervate at pH 5.75-6.5 and assembled into amorphous precipitates at higher pH. As the pH dropped from 8 to 6, the number of binding sites of the complex decreased in half, and the desolvation degree corresponding to the entropy gain was greatly reduced, conducing to the formation of coacervates rather than precipitates. The coacervates achieved the unique dynamic exchange by exchanging proteins with the diluted phase, making the uniform distribution of proteins in coacervates. The lysozyme activity was completely retained in β-conglycinin/lysozyme coacervates. These results proved that β-conglycinin-based heteroprotein complex coacervate is a feasible method to encapsulate and enrich active proteins in a purely aqueous environment.

The development of biocompatible Pickering stabilizers for oil-in-water emulsions has attracted fast increasing interests, due to their potential applications in food and pharmaceutical formulations. This work reports that a kind of novel nanoparticles to perform as outstanding Pickering stabilizers can be facilely fabricated from insoluble soybean polysaccharides (ISP) of Okara (a byproduct of soybean processing) by a high power ultrasonication. The ultrasonication resulted in breakdown of polysaccharide-based fibres in the ISP, and subsequently, formation of nanoparticles with sizes of 127–221 nm. The nanoparticles were mainly composed of polysaccharides and proteins, possessing a lower crystallinity of cellulose (relative to ISP) and good interfacial adsorption at oil-water interface. They were demonstrated to exhibit an excellent emulsification performance and a high tendency to form a gel-like network in the Pickering emulsions. Increasing the particle concentration and/or oil volume fraction was favorable for the creaming stability of the emulsions. Most of the droplets in the emulsions at higher particle-to-oil ratios were present in a more flocculated state, which was maintained by the hydrophobic interactions, as well as a bridging particle monolayer (with two droplets sharing the same monolayer). Interestingly, a portion of fine oil droplets with sizes

Pickering High Internal Phase Emulsions (HIPEs) stabilized by food-grade particles have received considerable attention. In this work, we first demonstrated the use of chitosan-caseinophosphopeptides (CS-CPP) nanocomplexes as particulate emulsifiers to stabilize the interface of natural oils and water. For this purpose, we developed the CS-CPP nanocomplexes through electrostatic interactions and demonstrated their application in the formation of stable Pickering HIPEs. The microstructures, e.g., interfacial frameworks, of the CS-CPP nanocomplexes partition between the continuous phase and interfacial region, and the states of the droplets of Pickering HIPEs were visualized by confocal laser scanning microscopy (CLSM) and an optical microscope. The compressed droplets in Pickering HIPEs formed a percolating 3D-network framework that endowed emulsions with viscoelastic, self-supporting, and ideal thixotropic features. In addition, the gelatinous state of Pickering HIPEs combined with robust and compact CS-CPP nanocomplexes formed an interfacial layer around the droplets, thus depressing the oxidation of linseed oil. The contents of primary and secondary oxidation products in HIPEs were lower than that in bulk oil and emulsions stabilized by surfactants. An in vitro gastrointestinal (GI) model was constructed to characterize the lipid oxidation, lipid digestion and curcumin bioaccessibility of Pickering HIPEs. Interestingly, this route enhanced the bioaccessibility of curcumin from 20.49% (bulk oil) to 49.21% (Pickering HIPEs). This work offers a facile method to develop Pickering HIPEs by food-grade particles, which help to fill the gap between the performance of CS-CPP nanocomplexes-stabilized Pickering HIPEs and potential applications as oral delivery systems of nutraceuticals.

Soy proteins as an important food ingredient have been widely applied in food formulations, due to their good nutritional value, high functionalities, and health-benefiting effects. Evidences have been fast accumulating to indicate that soy proteins are a kind of excellent building materials to be fabricated into a variety of nanostructured delivery systems for food bioactive ingredients. This review mainly presents the state-of-the-art knowledge about the fabrication of different kinds of nanostructures of soy proteins, as well as their applications to perform as nanocarriers for bioactives, achieved during the past decade. The composition, structure and physicochemical properties of soy proteins (including glycinin, β-conglycinin, and soy protein isolate) are first summarized. Then, the main strategies and techniques to fabricate a variety of nanostructured soy proteins are reviewed, including heat-induced aggregation, complexation with polysaccharides, emulsification-evaporatioin, desolvation/solvent displacement, crosslinking, self-assembly, electrospraying, nanoemulsions and interfacially nanostructured emulsions. Lastly, the feasibility of these nanostructured soy proteins (especially nanoparticles) to peroform as effective nanocarriers or delivery systems for bioactives are discussed. Due to the fast increasing interest of the food industry and consumer health awareness for the incorporation of soy proteins in functional food formulations, this review is of importance for guiding the development of novel ‘dual-function’ nanostructured soy protein-bioactive formulations.

The development of protein-based particles or nanoparticles to act as efficient (nano)carriers for poorly soluble nutraceuticals has attracted increasing interests in the food and pharmaceutical fields. In the work, we reported a novel ethanol-assisted disassembly and reassembly strategy to fabricate a kind of soy β-conglycinin (β-CG; a major storage globulin from soybeans) nanoparticles to perform as highly efficient nanocarriers for hydrophobic nutraceuticals (using curcumin as a model bioactive). When the β-CG was treated by ethanol at high concentrations ([E]; e.g., >30%, v/v), its structure gradually unfolded, and accordingly, the protein denaturation and aggregation occurred. When the ethanol was removed by a dialysis, the denatured and aggregated β-CG would further reassemble to form nanostructured particles. The size and morphology of these reassembled particles could be well modulated by varying the initial [E] in the range 30–70% (v/v). In general, increasing the [E] led to a progressive increase in protein aggregation, as well as a strengthening of particle compactness. In addition, the presence of curcumin in the ethanol solutions greatly accelerated the ethanol-induced aggregation of the protein, or facilitated the formation of large reassembled particles. Interestingly, the reassembled β-CG particles at [E] = 40% exhibited a highest capacity to load curcumin, with a maximal loading amount reaching approximately 13.7 g curcumin/100 g protein. The encapsulation performance of curcumin in these reassembled particles was closely associated with the extent and rate of ethanol-induced structural unfolding and aggregation of β-CG. The curcumin encapsulated in these reassembled particles exhibited a much greater stability and bioaccessibility than free curcumin. The findings provide a facile and food-biocompatible process to develop soy protein-based nanoparticles as efficient carriers for poorly soluble nutraceuticals, thus exhibiting a great potential to be applied in food and pharmaceutical fields.

Pickering high internal-phase emulsions (HIPEs) and porous materials derived from the Pickering HIPEs have received increased attention in various research fields. Nevertheless, nondegradable inorganic and synthetic stabilizers present toxicity risks, thus greatly limiting their wider applications. In this work, we successfully developed nontoxic porous materials through the Pickering HIPE-templating process without chemical reactions. The obtained porous materials exhibited appreciable absorption capacity to corn oil and reached the state of saturated absorption within 3 min. The Pickering HIPE templates were stabilized by gliadin-chitosan complex particles (GCCPs), in which the volume fraction of the dispersed phase (90%) was the highest of all reported food-grade-particle-stabilized Pickering HIPEs so far, further contributing to the interconnected pore structure and high porosity (>90%) of porous materials. The interfacial particle barrier (Pickering mechanism) and three-dimensional network formed by the GCCPs in the continuous phase play crucial roles in stabilization of HIPEs with viscoelastic and self-supporting attributes and also facilitate the development of porous materials with designed pore structure. These materials, with favorable biocompatibility and biodegradability, possess excellent application prospects in foods, pharmaceuticals, materials, environmental applications, and so on.

There is increasing interest in improving the freeze-thaw stability of emulsions by interfacial engineering in the food colloid field. The present work reported that for Pickering emulsions stabilized by heat-induced soy protein isolate (SPI) nanoparticles, their freeze-thaw stability could be well modulated by modifying the characteristics of the nanoparticles. The SPI nanoparticles with different characteristics (e.g., particle size, surface hydrophobicity) were obtained by heating the SPI solutions at initial concentrations (ci) of 0.25–6.0 wt% at 95 °C for 15 min. All the initial Pickering emulsions were formed at an oil fraction of 0.4 and protein concentration of 0.25 wt% in the aqueous phase, in the presence of 300 mM NaCl. In general, increasing the ci resulted in a progressive enhancement in freeze-thaw stability of the emulsions against creaming and coalescence, but accelerated the flocculation. The higher creaming stability at higher ci values seemed to be closely associated with the enhanced coalescence stability, as well as the strengthened gel-like network of these initial emulsions. There were close interplays between the freeze-thaw stability and the properties of the initial emulsions, or characteristics (e.g. particle size or surface hydrophobicity) of heat-induced SPI nanoparticles. The results confirmed that the SPI nanoparticles with larger sizes, higher surface hydrophobicity and more efficient packing at interface exhibit a greater potential to produce Pickering emulsions with higher freeze-thaw stability. The findings would be of relevance for understanding the freeze-thaw stability of Pickering emulsions stabilized by protein-based particles, as well as for the development of protein-stabilized emulsion formulations with a high freeze-thaw stability.

The development of cholesterol-free mayonnaise has attracted increasing interest in the food colloid field, due to the potential health concerns as a result of consumption of cholesterol-rich mayonnaise. One effective strategy in this regard is to substitute or partially substitute egg yolk with other organic emulsifiers and stabilizers, without affecting the quality of the product. In the work, we reported an effective strategy to fabricate high freeze-thaw-stability high internal phase emulsions (HIPEs), using complexes of a heated soy protein isolate (SPI) and chitosan (CS) at pH 3.0 as the emulsifiers and stabilizers. The SPI/CS complexes, formed even at a very low CS-to-SPI ratio, e.g., 1:10, showed a high capacity to stabilize HIPEs with a high freeze-thaw stability. Increasing the CS-to-SPI ratio in the complexes resulted in a progressive strengthening of gel network in the corresponding HIPEs, together with a gradual improvement of emulsification performance. The gel network of the HIPEs stabilized by the SPI/CS complexes was mainly maintained by the inter-droplet noncovalent interactions involving the CS molecules. The presence of CS also progressively increased the percentage of adsorbed proteins at the interface, and decreased the surface coverage of proteins at the interface. The high freeze-thaw stability of such HIPEs might be unrelated to the ice crystal formation during the freezing, and was more likely associated with the strong steric repulsion contributed to the adsorbed CS molecules between different droplets. The results indicated that the complexation of heated SPI and CS could provide an effective strategy to facilely fabricate outstanding freeze-thaw-stability HI PEs as potential mayonnaise replacers.

Nanoencapsulation of hydrophobic nutraceuticals with food ingredients has become one of topical research subjects in food science and pharmaceutical fields. To fabricate food protein-based nano-architectures as nanovehicles is one of effective strategies or approaches to improve water solubility, stability, bioavailability and bioactivities of poorly soluble or hydrophobic nutraceuticals. Milk proteins or their components exhibit a great potential to assemble or co-assemble with other components into a variety of nano-architectures (e.g., nano-micelles, nanocomplexes, nanogels, or nanoparticles) as potential nanovehicles for encapsulation and delivery of nutraceuticals. This article provides a comprehensive review about the state-of-art knowledge in utilizing milk proteins to assemble or co-assemble into a variety of nano-architectures as promising encapsulation and delivery nano-systems for hydrophobic nutraceuticals. First, a brief summary about composition, structure and physicochemical properties of milk proteins, especially caseins (or casein micelles) and whey proteins, is presented. Then, the disassembly and reassembly behavior of caseins or whey proteins into nano-architectures is critically reviewed. For caseins, casein micelles can be dissociated and further re-associated into novel micelles, through pH- or high hydrostatic pressure-mediated disassembly and reassembly strategy, or can be directly formed from caseinates through a reassembly process. In contrast, the assembly of whey protein into nano-architectures usually needs a structural unfolding and subsequent aggregation process, which can be induced by heating, enzymatic hydrolysis, high hydrostatic pressure and ethanol treatments. Third, the co-assembly of milk proteins with other components into nano-architectures is also summarized. Last, the potential and effectiveness of assembled milk protein nano-architectures, including reassembled casein micelles, thermally induced whey protein nano-aggregates, α-lactalbumin nanotubes or nanospheres, co-assembled milk protein-polysaccharide nanocomplexes or nanoparticles, as nanovehicles for nutraceuticals (especially those hydrophobic) are comprehensively reviewed. Due to the fact that milk proteins are an important part of diets for human nutrition and health, the review is of crucial importance not only for the development of novel milk protein-based functional foods enriched with hydrophobic nutraceuticals, but also for providing the newest knowledge in the utilization of food protein assembly behavior in the nanoencapsulation of nutraceuticals.

Use of protein-based nanovehicles has been well recognized to be one of the most effective strategies to improve water dispersibility, stability and bioavailability of nutraceuticals or bioactive ingredients. Thanks to their health-benefiting effects and unique assembly behavior, soy proteins seem to be the perfect food proteins for fabricating nanovehicles in this regard. This review presents the state-of-art knowledge about the assembly of soy proteins into nano-architectures, e. g., nanoparticles, nanocomplexes or nanogels, induced by different physicochemical strategies and approaches. The strategies to trigger the assembly of soy proteins into a variety of nano-architectures are highlighted and critically reviewed. Such strategies include heating, enzymatic hydrolysis, pH shift, urea or ethanol treatment, reduction, and static high pressure treatment. The self-assembly behavior of soy proteins (native or denatured) is also reviewed. Besides the assembly of proteins alone, soy proteins can co-assemble with polysaccharides to form versatile nano-architectures, through different processes, e.g., heating or ultrasonication. Finally, recent progress in the development of assembled soy protein nano-architectures as nanovehicles for hydrophobic nutraceuticals is briefly summarized. With the fast increasing health awareness for natural and safe functional foods, this review is of crucial relevance for providing an important strategy to develop a kind of novel soy protein-based functional foods with dual-function health effects from soy proteins and nutraceuticals.

Although the cholesterol-lowering benefits of soy proteins have been well recognized for a long time, the importance of protein structural characteristics to their cholesterol-lowering activities is little understood. In the work, we reported that a mild preheating at 95 °C for 20 min could remarkably improve the cholesterol-lowering activities of soy protein isolate (SPI) after an in vitro simulated pepsin-pancreatin digestion, including cholesterol and bile acids binding capacities (CBC and BBC), and inhibition of micellar cholesterol solubility (MCI), while an extensive preheating at 121 °C contrarily impaired its potential. The improvement of the cholesterol-lowering activities of the pepsin-pancreatin digest by the mild preheating was largely associated with the facilitated formation of digestion-induced peptide aggregates with high surface hydrophobicity (Ho) in the digest. The final pepsin-pancreatin digest of the mildly preheated SPI could be fractionated using a gradient ethanol precipitation technique at ethanol concentrations of 20–80% (v/v). The Ho and cholesterol-lowering activities of peptides in the resultant precipitate or supernatant fractions considerably varied. The ethanol-precipitated fractions at ethanol concentrations of 40–80%, with high Ho but low solubility (in water), largely contributed to the CBC of the digest, while all the precipitates obtained at ethanol concentrations of 20–80% dominated the BBC of the digest. In contrast, the soluble peptides in 80% ethanol were mainly responsible for the high potential of the digest to inhibit micellar cholesterol solubilization. In general, a good positive relationship between the CBC (or BBC) and Ho could be well observed for the pepsin-pancreatin digests of SPI, or their fractions. The MCI of the mildly preheated SPI digest was largely ascribed to the action of soluble peptides in 80% ethanol. The results demonstrated that the choice of preheating conditions (especially temperature) is of vital importance for optimal cholesterol-lowering benefits of soy proteins. The findings are also of interest for understanding the molecular mechanisms of the cholesterol-lowering activities of soy proteins.

The associative phase separation of biomacromolecules can produce both liquid-like coacervates or solid-like precipitates. In this study, we found that sodium chloride (NaCl) can programme the phase transition of β-conglycinin/lysozyme (β-CG/LYS) complexes. NaCl reduced the ζ-potential of both β-CG and LYS. Their complex coacervate was formed at pHs 6 and 7 with 5–80 mM NaCl and at pH 8 with 40–80 mM NaCl. Unlike the high critical salt concentration and entropy gain driving force of polyelectrolyte-based complex coacervation, 100 mM NaCl almost completely inhibited β-CG/LYS complexation, and the exothermic enthalpy change was the main driving force for β-CG/LYS complex formation. Confocal laser scanning microscopy with fluorescein isothiocyanate-labeled proteins demonstrated dynamic protein exchange in coacervate droplets, similar to that in polyelectrolyte-based complex coacervates.

In the work, the emulsifying properties of three representative globular proteins (soy β-conglycinin, glycinin and bovine serum albumin; designated as SC, SG and BSA, respectively) with different structural characteristics, as affected by the addition of NaCl (0–1000 mM), were investigated and compared, using two emulsion systems at oil fractions (o) of 0.2 and 0.8, respectively. The modulation of physicochemical properties and conformations of these three proteins by NaCl was first evaluated in terms of solubility, ζ-potential, surface hydrophobicity, particle size and intrinsic fluorescence profile. The electrostatic screening by the presence of appropriate concentrations (50–100 mM) of NaCl resulted in progressive increases in extent of protein aggregation and surface hydrophobicity of both SC and SG, but the addition of high concentrations (>300 mM) of NaCl was favorable for the ‘salting-in’ effects. At o = 0.2, the presence of NaCl impaired the emulsification performance of SC, while in the SG case, the emulsification performance was slightly affected. At o = 0.8, the presence of NaCl remarkably improved the emulsification performance of SC, and facilitated the droplet flocculation and gel network formation in the HIPEs, while in the SG case, the gel stiffness of the HIPEs was also improved. All the evidences indicated that at low o values, the influence of NaCl on the emulsifying properties of oligomeric globulins was dominated by the electrostatic screening effect, while at high o values (e.g., 0.8), the hydration repulsion between bound hydrated Na+ played a crucial role in the performance of these globulins as Pickering stabilizers. The findings are of importance for the understanding of the salt impact on the properties and stability of food protein emulsion formulations.

Complex coacervate is a classic charged polymer material in food science, personal care, and cellular biology. Nevertheless, time is often an important factor that is overlooked in the study of complex coacervates. This study analyzed the dynamic equilibrium/relaxation behavior of β-conglycinin/lysozyme (β-CG/LYS) heteroprotein coacervates after mixing, especially the effect of NaCl concentration, total protein concentration, and pH on this equilibrium behavior, only using two simple but effective methods (turbidity kinetics and bright-field microscopy). Although the turbidity kinetics of the β-CG/LYS coacervates experienced rapid initial growth like soluble complexes and amorphous precipitates, it subsequently showed a unique decline behavior. Through bright-field microscopy, we found that the drop in turbidity was closely related to the dynamic equilibrium of β-CG/LYS coacervates, including the shape-transformation from non-spherical clusters to spherical coacervates and the gradual merging of small coacervates. Adding NaCl (0, 20, and 40 mM), increasing the total protein concentration (1 and 5 mg/mL), and lowering pH (6 and 8) all accelerated the dynamic equilibrium of the β-CG/LYS coacervate and reduced the relaxation time. Turbidity kinetics can be used as a screening method to evaluate the effect of various factors on the dynamic equilibrium/relaxation behavior of coacervates.

Porous materials derived from natural and biodegradable polymers have received growing interest. We demonstrate here an attractive method for the preparation of protein-based porous materials using emulsions stabilized by gliadin-chitosan hybrid particles (GCHPs) as the template, with the addition of gelatin and kosmotropic ions to improve the mechanical strength. The microstructure, mechanical properties, cytotoxicity, and fluid absorption behavior of porous materials were systematically investigated. This strategy facilitated the formation of porous materials with highly open and interconnected pore structure, which can be manipulated by altering the mass ratio of hexane or gelatin in the matrix. The Hofmeister effect resulted from kosmotropic ions greatly enhanced the Young's modulus and the compressive stress at 40% strain of porous materials from 0.56 to 6.84 MPa and 0.26 to 1.11 MPa, respectively. The developed all-natural porous materials were nontoxic to HaCaT cells; they also had excellent liquid (i.e., simulated body fluid and rabbit blood) absorption performance and advantages in resisting stress and maintaining geometry shape. The effects of different concentration amounts and type of salts in the Hofmeister series on the formation and performance of porous materials were also explored. Mechanical strength of porous materials was gradually enhanced when the (NH4)2SO4 concentration increased from 0 to 35 wt %, and the other four kosmotropic salts, including Na2S2O3, Na2CO3, NaH2PO4, and Na2SO4, also showed positive effects. This work opens a simple and feasible way to produce nontoxic and biodegradable porous materials with favorable mechanical strength and controllable pore structure. These materials have broad potential application in many fields involving biomedical and material science, such as cell culture, (bio)catalysis, and wound or bone defect healing.

A softer natural Pickering nanostabilizer, S-ovalbumin (S-OVA) was reported in this work, based on our previous researches about soft globular protein nanoparticles. Compared with native OVA, S-OVA has higher surface hydrophobicity, greater conformational flexibility and thinner tightly-bond water layer, which make it be unfolded more highly at the oil-water interface. However, S-OVA also possesses higher zeta-potential and thicker closely-surrounding water layer, offering it stronger electrostatic repulsion and steric hindrance between molecules and increased intramolecular cohesion. The improvements guarantee S-OVA undisintegrated particle structure and independent state on the interface and high refolding off the interface. The more flexible interior and firmer exterior together endow a higher softness to S-OVA. The HIPPE gels solely stabilized by S-OVA were fabricated using one-step shearing. These HIPPE gels own steady network structure mainly supported by bridging flocculation, strong self-supporting ability and moldability. The high storage stability and ability to inhibiting lipid oxidization provide the HIPPE gels an enormous potential in encapsulating and protecting volatile, easily-oxidized or dangerous organic liquids, during the storage and transportation. The attractive temperature responsiveness offers a high convenience to re-obtaining the organic liquids. And a re-encapsulation can be easily achieved via a re-shearing. The heat-enhanced gel intensity and moldability mean the HIPPE gels can be applied to produce dualistic gels or porous scaffolds with latent applications. These findings are helpful to explore more new Pickering stabilizers from the nature and extend the applications of HIPPEs in highly-demanded and high-tech industries.

There is increasing interest in the development of Pickering emulsions stabilized by food grade (nano) particles, due to their promising applications in food formulations. The work reports for the first time that starch nanocrystals (SNCs) prepared by sulfuric acid hydrolysis from native waxy maize starch exhibit a great potential to act as sole effective stabilizer for oil-in-water high internal phase emulsions (HIPEs). Relative to the native starch, the SNCs had more irregular and agglomerated morphology, and significantly higher crystallinity and hydrophobicity. The particle size and ζ-potential of the SNCs considerably varied with pH and/or ionic strength. The formation, microstructure and properties of stable HIPEs were characterized by visual observations, optical microscopy and dynamic oscillary measurements. The results indicated that at a given particle concentration in the continuous phase (1.0 wt%), stable and gel-like HIPEs were formed at oil internal phase (ϕ) values of 0.75–0.85; increasing the particle concentration led to the formation of gel-like HIPEs with stronger stiffness; in the absence of NaCl, stable and gel-like HIPEs were formed only at pH values of 5.0–10.0, and increasing the pH persistently decreased the emulsion size (and accordingly, increased the gel stiffness); increasing the ionic strength from 0 to 400 mM resulted in a progressive impairment of the emulsification performance, as well as of the formation of stable HIPEs. The findings would be of great relevance for the development of HIPEs stabilized by SNCs appropriate to be applied in the food formulations.

The development of high internal phase emulsions (HIPEs) stabilized by food-grade particles (e.g., cellulose nanocrystals, CNCs) has attracted increasing interests in the food colloid field. This paper reports a type of oil-in-water HIPEs using protein (bovine serum albumin, BSA)-covered CNCs as effective stabilizers. The BSA-covered CNCs were simply obtained by mixing aqueous solutions of anionic CNCs with the cationic BSA at pH 3.0. Turbidity and absorption measurements proved the binding of BSA to CNCs. The strong interaction and aggregation of BSA-covered CNCs were verified by atomic force microscopy measurements. Interestingly, the 0.5% (w/v) CNCs covered with a low amount of BSA (0.01%–0.1%, w/v) as the emulsifying agent yielded very stable, gel-like HIPEs (ϕ = 0.8). The stiffness and microstructure of the HIPEs can be modulated either by changing the surface protein coverage at a fixed CNC concentration or by changing the concentration of CNCs with a fixed surface protein coverage (e.g., 80%). The improvement of the stiffness was largely attributed to the enhanced droplet packing effect and interfacial bridging effect. These findings offer a promising opportunity to extend the applications of protein-modified CNCs in the food and pharmaceutical industries.

Biodegradable food packaging is sustainable and has a great application prospect. PLA is a promising alternative for petroleum-derived polymers. However, PLA packaging suffers from poor barrier properties compared with petroleum-derived ones. To address this issue, we designed bilayer films based on PLA and Pickering emulsions. The formed bilayer films were compact and uniform and double layers were combined firmly. This strategy enhanced mechanical resistance, ductility and moisture barrier of Pickering emulsion films, and concomitantly enhanced the oxygen barrier for PLA films. Thymol loadings in Pickering emulsion layer endowed them with antimicrobial and antioxidant activity. The release profile of thymol was well fitted with Fick's second law. The antimicrobial activity of the films depended on film types, and Pickering emulsion layer presented larger inhibition zone than PLA layer, hinting that the films possessed directional releasing role. This study opens a promising route to fabricate bilayer architecture creating synergism of each layer.

The high hydrophilicity of cellulose nanocrystals (CNCs) greatly limits their application in the Pickering emulsion formulations. The work for the first time reports that a simple surface modification with octenyl succinic anhydride (OSA; food-grade) can remarkably improve the emulsification performance of CNCs, and facilitate the fabrication of the Pickering high-internal-phase-emulsions (HIPEs). The OSA modification occurred between the corresponding anhydride and the surface hydroxyl groups of CNCs, which remarkably increased their surface hydrophobicity. Stable and gel-like Pickering HIPEs with fine droplets could be easily fabricated using OSA-modified CNCs, even at very low particle concentrations in aqueous phase. The findings would be of crucial importance for greatly extending the applications of CNCs in emulsion formulations in the food and pharmaceutical fields.

This work attempted to engineer emulsions' interface using the special affinity between proline-rich gliadin and proanthocyanidins (PA), to develop surfactant-free antioxidant Pickering emulsions with digestive-resistant properties. This binding interaction between gliadin and PA benefited the interfacial adsorption of the particles to corn oil droplets. Pickering droplets as building units assembled into an interconnected three-dimensional network structure, giving the emulsions viscoelasticity and ultrastability. Oxidative markers in Pickering emulsions were periodically monitored under thermally accelerated storage. Lipid digestion and oxidation fates were characterized using in vitro gastrointestinal (GI) models. The interfacial membrane constructed by antioxidant particles served as a valid barrier against lipid oxidation and digestion, in a PA dose-dependent manner. Briefly, lipid oxidation under storage and simulated GI tract was retarded. Free fatty acid (FFA) fraction released decreased by 55% from 87.9% (bulk oil) to 39.5% (Pickering emulsion), implying engineering interfacial architecture potentially benefited to fight obesity. This study opens a facile strategy to tune lipid oxidation and digestion profiles through the cooperation of the Pickering principle and the interfacial delivery of antioxidants.

In this paper, we demonstrate for the first time the use of gliadin particles to structure algal oil (rich in DHA) and to exert chemical stability against lipid oxidation via the Pickering high internal phase emulsion (HIPE) strategy. The gliadin/chitosan colloid particles (GCCPs) were effectively adsorbed and anchored at the algal oil-water interface. Concomitantly, the particle-coated droplets as building blocks constructed a percolating 3D-network framework, endowing Pickering HIPEs with viscoelastic and self-supporting attributes. In addition, Pickering HIPEs loaded with shell (HIP-curEs) or core curcumin (HIPEs-cur) were constructed to depress the oxidation of algal oil. The content of primary (lipid hydroperoxides) and secondary (malondialdehyde and hexanal) oxidation products in HIPEs was lower than that in bulk oil. The oxidative stability of HIPEs was further improved in shell and core curcumin. An in vitro gastrointestinal (GI) model was constructed to characterize the lipid digestion, lipid oxidation as well as curcumin bioaccessibility of the ingested Pickering HIPEs. Lipid oxidation in the Pickering HIPEs was retarded under GI fluids, especially in the presence of core curcumin. The free fatty acid (FFA) fraction released was below 30% for all HIPEs, reflecting that the Pickering HIPEs formed restrict the digestion of fat or oil and potentially help to fight obesity. Interestingly, this route enhanced the bioaccessibility of curcumin from only 2.13% (bulk algal oil) to 53.61% (core curcumin); in particular, it reached 76.82% for shell curcumin. These results help to fill the gap between the physicochemical performance of the gliadin particle stabilized Pickering HIPEs and their potential applications as oral delivery systems of nutraceuticals. This work opens concomitantly an attractive strategy to convert liquid oils into antioxidant soft solids without artificial trans fats, as a potential alternative for PHOs.

There is still a debate about the influence of salts on the freeze-thaw stability of emulsions. In this research, the influence of the NaCl addition (before or after the emulsification; 100–500 mM) on the freeze-thaw stability of the Pickering emulsions stabilized by heat-induced soy protein isolate (SPI) nanoparticles, at a given protein concentration of 1.0% (w/v) and oil fraction of 0.4, was investigated. The addition of NaCl resulted in considerable changes in particle characteristics (including particle size, surface hydrophobicity and ζ -potential) of the SPI nanoparticles, with the extent of the changes varying with the applied ionic strength ( μ ). Despite the NaCl addition before or after the emulsification, the presence of NaCl remarkably improved the freeze-thaw stability against droplet coalescence and creaming of the emulsions, though the improvement was related to the applied μ . The improvement of the freeze-thaw stability would be largely attributed to the strengthening of the interfacial protein or protein nanoparticle films coating droplets, rather than the inhibition of ice crystal formation by the presence of NaCl. If the salt was introduced before the emulsification, a gel-like network might be formed in the corresponding emulsions, which would further provide an additional stabilization against the freeze-thaw treatment. Optimal freeze-thaw stability was observed in the presence of appropriate concentrations of NaCl (e.g., 100–200 mM). This is the first report to indicate the importance of the electrostatic screening to the improvement of the Pickering emulsions stabilized by charged particles. The findings would be of great importance for the formulation of food grade emulsions with excellent freeze-thaw stability.

In the work, we report a kind of novel highly transparent oil-in-water (O/W) HIPE gels stabilized solely by c-phycocyanin (CPC; an important biliprotein pigment), with a great potential to act as outstanding containers for heat or UV labile lipophilic bioactives. The CPC was solubilized in 6 M urea solution containing 40 wt% glycerol, in order to achieve the improved emulsification performance of the protein, as well as the transparency of the resultant HIPE gels through the refractive index (RI) matching between the aqueous and dispersed oil (dodacane) phases. Using 6 M urea containing 40 wt% glycerol as the aqueous phase, the transparent HIPE gels could be formed at the CPC concentration (c) as low as 0.1 wt%, and oil fractions in the range 0.6–0.86. In the protein-poor regime, e.g., c

Incorporation of hydrophobic and poorly soluble nutraceuticals into food formulations is among the great challenges in food science and pharmaceutical fields. One effective strategy to meet this challenge is to develop a kind of food-compatible nanovehicles for improving water solubility, stability, bioavailability and bioactivities of these nutraceuticals. Many food protein-based nano-architectures, e.g., nanoparticles, nano-complexes, nanogels, nano-micelles, nanofibers or nanotubes, have been demonstrated to perform as outstanding nanovehicles in this regard. They are not only nutritional/digestible, safe, and easy to prepare and handle, but also have high encapsulation performance and nutraceutical loading capacity. In some cases, the encapsulation in these nanovehicles can impart an intestine-targeted and controlled delivery function to encapsulated nutraceuticals. In this paper, the assembly of milk and soy proteins into a variety of nano-architectures, as potential nanovehicles for hydrophobic nutraceuticals is critically reviewed. The strategies to trigger the assembly, or disassembly/reassembly of naturally occurring nano-architectures (e.g., native soy oligomeric globulins and casein micelles), denatured and aggregated proteins (e.g., soy protein isolate and whey protein isolate), and monomeric globular proteins (e.g., β-lactoglobulin) are highlighted. The general principles of protein self-assembly are also discussed. Due to the fast increasing interests for the incorporation of hydrophobic nutraceuticals in many novel food formulations, this review is of relevance for providing a state-of-art knowledge about the strategies and approaches to develop food protein-based nano-architectures as effective nanovehicles for nutraceuticals.

The added-value utilization of okara, a major byproduct of soybean processing, has attracted increasing interests, due to its good nutrition, functionalities and health-promoting effects. This work reports a facile and green process to prepare highly functional holocellulose nanofibers (hCNFs) from the insoluble polysaccharides (ISP) of okara, using a mild alkali planetary ball milling technique. The ball milling for 10–25 h in the presence of 1.0 wt% NaOH could efficiently transform the ISP into water dispersible hCNFs with highly crystalline cellulose contents reaching around 80%. The crystallinity of cellulose in these hCNFs was around 60%. The surface hydrophobicity of these hCNFs progressively decreased with increasing the milling time from 0 to 25 h, and their ζ-potential was independent of milling time. The hCNFs were demonstrated to perform as outstanding Pickering stabilizers for oil-in-water emulsions, with much better emulsification performance and emulsion stability than the ISP. All the emulsions at an oil fraction of 0.2 could be well stabilized by these hCNFs at a particle concentration in the aqueous phase of 0.1 wt%. Among all the hCNFs, those obtained after the milling of 10–20 h had highest potential to stabilize fine emulsions. All the emulsions stabilized by the hCNFs were prone to fast creaming, but the creamed emulsions exhibited excellent storage stability. The emulsifying properties of the hCNFs were closely associated with their interfacial adsorption at oil-water interface. The findings would be of importance not only for guiding the added-value utilization of underutilized byproducts of agricultural products, but also for providing a facile and green process to prepare highly functional hCNFs from okara.

Summary Biodegradable food packaging promises a more sustainable future. Poly(lactic acid) (PLA) is a promising alternative for petroleum-derived polymers. However, PLA films suffer from poor barrier properties compared with petroleum-derived ones. To address this issue, we designed bilayer and sandwich-architectured trilayer films based on PLA and gliadin. We reported firstly the direct formation of PLA–gliadin bilayer/trilayer films without surface modification on PLA film. The films were compact and uniform, and double/triple layers were combined firmly, preventing delamination. This strategy enhanced mechanical resistance, ductility and moisture barrier of gliadin films and concomitantly enhanced the oxygen barrier for PLA films. Thymol loadings endowed bilayer/trilayer films with antimicrobial activity and antioxidant activity. The antimicrobial activity of the films depended on film types, and gliadin layer presented larger inhibition zone than PLA layer, hinting that the films possessed directional releasing role. This study opens a promising route to fabricate bilayer/trilayer architecture helping to create synergism of the biopolymers.

Herein, we report firstly the development of sustained antimicrobial and antioxidant gelatin-lysozyme films crosslinked by the oligomeric proanthocyanidins (OPCs), a duel-functional agent. Lysozyme release kinetic studies were performed at neutral and acidic pH, and they could be described as a biphasic process. OPCs crosslinking retarded lysozyme release at pH 7.0, in a dose dependent manner, and the inhibition zone tests confirmed that the sustained release of lysozyme was realized upon weak crosslinking with OPCs. OPCs crosslinking enhanced thermal stability of the gelatin films, and gave them the ability to barrier ultraviolet light. OPCs loadings endowed the films excellent antioxidant activities, the DPPH radical scavenging activity of the films increased linearly to 93.97% upon increasing OPCs loadings from 0 to 2.0%. Concomitantly, the reducing powder of the films increased linearly from 6.08 ± 0.09 to 45.53 ± 2.74 μmol Asc Acid/g film. Additionally, the antioxidant properties of gelatin films against lipid oxidation in edible oils were evaluated. Lipid hydroperoxides of algal oils in the gelatin bags were approximately a quarter of that in low-density polyethylene (LDPE)-based bags, and the malondialdehyde (MDA) values of algal oils were lower than that in LDPE-based bags by 1–2 orders of magnitude. Regrettably, the incorporation of OPCs did not enhance the antioxidant capability of gelatin films against lipid oxidation in wrapped edible oils, possibly due to the limited release toward algal oils in term of its oil-soluble attribute. This study opens a promising pathway for producing sustained antimicrobial and antioxidant gelatin films using a bi-functional agent.

We report for the first time the usage of mono-dispersed gliadin/chitosan hybrid particles as a particulate emulsifier for Pickering high internal phase emulsions (HIPEs) development. The hybrid particles with partial wettability were fabricated at pH 5.0 using a facile anti-solvent route. Stable Pickering HIPEs with internal phases of up to 83% can be prepared with low particle concentrations (0.5-2%). The hybrid latexes were effectively adsorbed and anchored at the oil-water interface to exert steric hindrance against coalescence. Concomitantly, the compressed droplets in Pickering HIPEs to form a percolating 3D-network framework endowed the emulsions viscoelastic and self-standing features. The protective effect of Pickering HIPEs on curcumin was confirmed, and the content of primary oxidation products in HIPEs was slightly lower than that in bulk oil. This work opens an attractive strategy to convert liquid oils to viscoelastic soft solids without artificial trans fats, as a potential alternative for PHOs.

The freeze-thaw stability of Pickering emulsions stabilized by (nano)particles from heated soy protein isolate (SPI) and whey protein (WP), was investigated and compared with those stabilized by unheated SPI (or WP) and sodium caseinate (NaCN). The stability was evaluated in terms of flocculation and coalescence degrees, and creaming index, as well as differential scanning calorimetry (DSC) characteristics. The emulsions exhibited different patterns of freeze-thaw stability, depending on the type of applied proteins, as well as the cycle number of freeze-thaw treatment. In general, the emulsions stabilized by heated SPI and WP exhibited much better freeze-thaw stability against coalescence and creaming, than those by unheated counterparts. The freeze-thaw stability against creaming of the heated SPI emulsion was even much better than that of the NaCN emulsion. The emulsions stabilized by SPI or WP, unheated or heated, showed poor freeze-thaw stability against flocculation. The differences in freeze-thaw stability between different emulsions could be explained in terms of the differences in physicochemical parameters of proteins or protein particles, as well as their microstructure. The good freeze-thaw stability of the emulsions by heated SPI and WP might be largely due to the action of Pickering steric stabilization, while the gel-like network formation also attributed to the stability. The results would be of great importance for the fabrication of Pickering emulsions stabilized by food protein particles and their applications in food formulations.

This study investigated structure and morphology of starch spherulites prepared from debranched waxy maize and waxy potato starches. Debranched waxy potato starch favored the formation of B-type crystals with longer branch chains (average chain length, 26.14), whereas A-type polymorphic aggregates were generated from debranched waxy maize under same recrystallization condition. Spherulites had smaller particle size distribution (D[3,2], ∼3.7μm), higher dissociation temperature (80-120°C) and crystallinity (80∼90%), compared to native waxy starches. Intact spherulites could be used as an edible particle emulsifier after modifying by octenylsuccinic anhydride (OSA). The emulsion produced using 2wt.% of octenylsuccinate (OS) starch spherulites as emulsifier was quite stable over 2months, and its Pickering emulsions displayed protective effect on stability of oil droplets.

Soy proteins as important food ingredients exhibit a great potential to be widely applied in food formulations, due to their good nutrition, functional properties and health effects. The knowledge about the structure-function relationships of these proteins is crucial for their applications, but still very scant, especially that on their molecular mechanism of emulsification. The purpose of this review is to present a comprehensive summary of the knowledge about emulsifying and interfacial properties of soy proteins, achieved during the past decades, and particularly to provide an insight in understanding the role of conformational flexibility in their emulsifying properties. The interplays between the emulsifying and interfacial properties are also elucidated. For these proteins, the conformational flexibility rather than the surface hydrophobicity is the crucial parameter determining their emulsification performance. On the other hand, evidence is fast growing to indicate that because of the insoluble nature, soy proteins are a kind of unique materials to perform as food-grade Pickering stabilizers. The knowledge about the Pickering emulsion stabilization is distinctly different from that for conventional emulsions stabilized by soy proteins. Thus, different strategies should be employed to develop soy proteins into a kind of effective emulsifiers, depending on the preference of emulsification performance or emulsion stability.

The development of food-grade Pickering stabilizers has recently attracted fast increasing interest in the food science field. The work reports a novel non-thermal process to fabricate soy protein isolate (SPI) nanoparticles to perform as effective Pickering stabilizers. The nanoparticles were formed by Ca 2+ -induced aggregation and subsequent glutaraldehyde (GAD) crosslinking. At a protein concentration of 2% (w/v), increasing Ca 2+ concentration (from 0 to 7.5 mM) led to a progressive increase in turbidity and particle size (60–130 nm), indicating aggregation and formation of nano-sized particles. The Ca 2+ -induced SPI nanoparticles, further treated with different concentrations of GAD (0–200% equivalents), were characterized in terms of particle size, surface hydrophobicity and charge, internal integrity, emulsification performance and interfacial packing, as well as emulsion stability. The results indicated that the crosslinking treatment resulted in larger particle sizes, lower surface hydrophobicity and higher surface charge, stronger internal integrity, lower emulsification performance and higher emulsion stability against coalescence, with the extent of changes increasing with the applied GAD concentration. The emulsions stabilized by these fabricated nanoparticles followed the rule of limited coalescence, and had a very low surface coverage (3.8–12.6%). The surface coverage is considerably lower than that of many Pickering emulsions previously reported in the literature. All the results confirmed that the fabricated SPI nanoparticles could perform as effective Pickering stabilizers. The findings would be of great importance for the development of food-grade Pickering stabilizers suitable for the formulations of functional foods and medicine.

There is increasing interest in developing food-grade coenzyme Q 10 (CoQ 10 ) ingredients for functional food formulations. This paper reported a spray-drying microencapsulation of CoQ 10 (in olive oil) using different food-grade biopolymers [soy protein isolate (SPI), pea protein isolate (PPI), defatted milk powder and octenylsuccinic anhydride-modified starch (OSA)] as the emulsifiers and wall materials, with the aim to improve its water solubility, stability and bioaccessibility. To improve the microencapsulation, maltodextrin (with a dextrose equivalent value of 16) was blended with the emulsifiers to produce the spray-dried microencapsulates. The type of proteins affected their physicochemical characteristics, including particle size, surface hydrophobicity and ξ -potential, which accordingly led to the differences in characteristics of the formed emulsions, e.g. droplet size and distribution profile, flocculated state of droplets, stability against coalescence and creaming, as well as interfacial protein concentration. All the microencapsulate preparations exhibited high encapsulation efficiency and good redispersion and/or dissolution behavior, though the encapsulation efficiency and dissolution behavior varied with the type of applied emulsifiers. The better encapsulation efficiency and dissolution behavior were largely related to the higher interfacial emulsifier concentration of the corresponding original emulsions. Furthermore, the microencapsulation remarkably improved the UV- or heat- stability, as well as the in vitro bioaccessibility of CoQ 10 . The improvement also distinctly varied with the type of applied emulsifiers. The results suggest that the spray-drying microencapsulation is an effective technique to improve the low water solubility and bioavailability of CoQ 10 , however, the choice of emulsifiers or wall materials is important for the optimization of the CoQ 10 encapsulation.

Native potato starch (PS) granules were separated into three size fractions: larger than 30 μm (P-L), 15–30 μm (P-M), and smaller than 15 μm (P-S). The morphological and crystalline structure of fractionated potato starches were investigated by light and scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The P-L fraction showed ellipsoidal shape and B-type X-ray pattern, whereas the P-S fraction had spherical shape and A-type pattern. The fluorophore-assisted capillary electrophoresis data showed that the P-L fraction had more B2 chains and less short A and B1 chains than the P-S counterparts. Smaller granules with larger specific surface area had higher degree of substitution when reacted with octenylsuccinic anhydride (OSA), and showed more uniform distribution of octenylsuccinate substituents. Both OSA modified and unmodified P-S samples showed higher flowability compared with the P-L counterparts.

Although the complexation between proteins and phenol compounds has been widely investigated for improved stability and delivery of those compounds, especially those with low solubility and bioavailability, few works are available addressing the influence on the functional properties of the proteins. The work investigated the influence of complexation with curcumin at pH 3.0 and 7.0 on the emulsifying properties and emulsion oxidative stability of soy protein isolate (SPI). At both test pH values, most of proteins in SPI were present in the nanoparticle form, with larger sizes, higher surface hydrophobicity and better emulsifying properties of these nanoparticles observed at pH 3.0. However, the emulsions at pH 3.0 were much more susceptible to lipid oxidation. The SPI at both pH values easily interacted with curcumin to form complexes at nanoscale, through hydrophobic interactions. The complexation at both pH values slightly changed the particle size, the absolute ξ -potential and emulsifying properties of the protein, but remarkably decreased their surface hydrophobicity. Furthermore, the complexation distinctly accelerated the lipid oxidation of the emulsions at both pH values. The results would be of importance for the development of functional soy protein ingredients enriched with some bioactive compounds.

In this paper, we demonstrate for the first time the use of gliadin colloid particles (GCPs) as an effective particulate stabilizer of oil-in-water emulsions of natural oils and water. For this purpose, we fabricated GCPs through a facile anti-solvent precipitation procedure and demonstrated their uses in the formation of Pickering emulsions as well as Pickering high internal phase emulsions (HIPEs). We found that unmodified GCPs can produce stable, surfactant-free o/w emulsions with microscale droplet sizes under experimental mixing conditions at pH 4 and above. In contrast, the emulsions were not stable against coalescence at ∼pH 3.0. The microstructures, e.g., interfacial framework, GCPs partition between the continuous phase and interfacial region, and state of the droplets, of Pickering emulsions as a function of pH were visualized by optical microscopy and confocal laser scanning microscopy (CLSM), confirming that in addition to Pickering stabilization, the GCPs-based network and/or dispersed droplets-based network also contributed to the stabilization of the emulsions, in a pH-dependent manner. Clear correlations exist between colloid properties of the GCPs dispersions and the emulsion characteristics. Interestingly, stable surfactant-free Pickering HIPEs were fabricated by a facile shearing emulsification. This study opens a promising route based on Pickering HIPEs to transform liquid oils into viscoelastic emulsion gels with zero trans-fat and less saturated fat. The Pickering HIPEs possess promising potentials to replace solid fat in food formulations, which outline new directions for future fundamental research.

The development of protein-based nanovehicles to improve water solubility, stability and bioavailability of hydrophobic or poorly soluble nutraceuticals has become a subject of fast increasing interest in the field. This review mainly presents the state-of-art knowledge about the utilization of naturally occurring nanostructured protein architectures (casein micelles, ferritin and legume oligomeric globulins) as nanovehicles for hydrophobic nutraceuticals or drugs, through a disassembly and reassembly strategy. First, the composition and structural features of these three naturally occurring architectures are briefly summarized. Then, many strategies and techniques to mediate the disassembly and reassembly of these naturally occurring architectures are comprehensively reviewed, including pH-, urea-, alcohol-, high pressure -, and heat-mediated disassembly and reassembly (or dissociation and reassociation). Last, reassembled casein micelles, ferritin (or apoferritin) and legume oligomeric protein nanoparticles are demonstrated to perform as outstanding nanovehicles for improving water dispersion, stability and bioactivities of many nutraceuticals or drugs. Due to the rapidly increasing consumer interests for health-benefiting foods, this review is of importance for the development of a kind of outstanding nanovehicles for nutraceuticals with a great potential to be applied in functional foods or drug formulations.