Tea is one of the most widely daily consumed beverages all over the world, and it is usually consumed with milk and/or soy milk. However, very few researches have studied the interactions between tea polyphenols (TPs) and soy milk proteins as compared with milk proteins. Here, we reported that epigallocatechin gallate (EGCG), a major component of TPs, can effectively inhibit the inhibitory activity of Kunitz trypsin inhibitor (KTI, a major antinutrient in soy milk). The mechanism of inactivation of KTI by EGCG was investigated by stopped-flow/fluorescence, thermodynamics, and docking studies. The results indicated that EGCG binds KTI via both hydrophobic and hydrophilic interactions with an association constant of 6.62 × 105 M–1 to form a 1:1 complex. Molecular docking showed the participation of amino acids includes three amino acid residues (Asn13, Pro72, and Trp117) near the reactive site of KTI, which may prevent KTI from contacting trypsin and hence inactivate KTI.Keywords: EGCG; inactivation; interaction; molecular docking; soybean Kunitz trypsin inhibitor; spectroscopy;

•Colloidal behavior of zein hydrolysate was considerably influenced by Xan.•Xan was successfully removed from zein hydrolysate under acidic pH condition.•High surface activity of zein hydrolysate was resulted from the presence of Xan.•Xan endowed zein hydrolysate with higher colloidal delivery capacity.The aims of this study were to investigate the effect of xanthophylls (Xan) on the colloidal property and interfacial activity of zein hydrolysate (ZH), and the influence of Xan on the colloidal delivery capacity of ZH was also studied by the construction of emulsions and colloidal particles systems. The result indicated that compared with color-free ZH (CF-ZH), ZH was more sensitive to pH and showed obvious aggregation behavior at acidic pH. ZH exhibited lower critical micelle concentration compared with CF-ZH, suggesting the higher amphiphilic characteristic of ZH. The results from interfacial activity investigations showed that ZH exhibited higher interfacial activity compared with CF-ZH, and the thickness and intensity of the interfacial layer constituted by ZH was increased as a result of the existences of Xan. Compared with CF-ZH, the emulsions stabilized by ZH possessing smaller size and higher physical stability, and the curcumin nanoparticles fabricated in ZH solutions showed higher encapsulation efficiency, smaller particle size, better monodispersity and higher zeta potential. In conclusion, the presence of Xan in ZH obviously changed the colloidal property and improved interfacial activity and colloidal delivery capacity of ZH itself, and it endowed ZH with more extensive application prospects.

•Soy protein(SP)/chitosan(CS) coacervation was driven by both entropy and enthalpy.•SP/CS coacervates had a viscoelastic solid behavior with gel-like microstructures.•SP/CS coacervated microcapsules had the advantage of higher encapsulation efficiency.•SP/CS coacervates showed improved stability against algal oil oxidation.Complex coacervation of soy protein isolate (SPI) with chitosan (CS) and the microencapsulation of algal oil using the SPI-CS coacervate were investigated. The ζ-potential and coacervate yield data showed that the optimal complexation pH and CS/SPI ratio were 6.0 and 0.125 g g−1, respectively. Isothermal titration calorimetry further confirmed that per molecule of SPI was saturated with 0.104 molecules of CS at pH 6.0, suggesting this binding was high affinity (Ka = 4.16 × 105 ± 0.09 × 105 M−1) and driven by both entropy and enthalpy. The rheological and microstructure measurement indicated that the SPI-CS coacervates had a viscoelastic solid behavior (G′ > G″) with highly interconnected gel-like network structures. The algal oil microcapsule fabricated by the SPI-CS coacervate showed advanced encapsulation efficiency and improved oxidative stability compared to the one encapsulated by SPI alone. The transglutaminase cross-linking could further improved the oxidative stability of SPI-CS microcapsule which proved by the reduced lipid hydroperoxides and volatile hexanal. This improvement was believed to be attributed to the antioxidant properties of CS as well as the increase of protection against oxidation by providing an oxygen barrier after complex coacervation and cross-linking.

•Pepsin-released soy peptide with a large amount of carboxyl amino acid was prepared.•Soy peptides functionalized CaP facilitate to construct stable Pickering emulsions.•pH switchable emulsion was obtained based on dissolution-recrystallization of CaP.Here we reported a food-grade Pickering emulsions with pH switchable properties based on soy peptides functionalized calcium phosphate particles (CaP). The nanometer crystalline CaP were synthesized according to the well-established wet chemical precipitation process followed by microfluidization treatment, and functionalized in situ with a pepsin released peptides of soy β-conglycinin. These peptides characterized with a large amount of carboxyl amino acid (Glu and Asp) residues, exhibit high affinity to CaP particles. The decoration of CaP particles with soy peptides enhanced their hydrophobic wettability and electrodynamics properties simultaneously. Hence, the surface modified CaP particles facilitate to construct interfacial crystal architecture and resulting stable Pickering emulsions and gels. The pH triggered switchable properties of the emulsion were established based on the pH-dependent dissolution-recrystallization transition of CaP. Stimuli-responsive Pickering emulsification will not only offer opportunity to create a sustainable way to improve oil and catalyst recovery, but also find interesting applications in food industry for phase release of the functional elements by on-demand strategies. The food grade status of both soy peptides and calcium phosphate might extend their applications for food industry.Download high-res image (194KB)Download full-size image

Herein, we report novel high internal phase emulsions and transparent oleogels that exhibit a hierarchical configuration by manipulating the spatial assembly of a natural small molecular-weight quillaja saponin for color performance. Quillaja saponin (QS) is a natural triterpenoid bidesmosidic from the soapbark tree (Quillaja saponaria Molina). Fairly monodispersed QS-coated nanodroplets (∼154 nm) were prepared using the ultrasonic emulsification strategy, and then used as block stabilizers for the fabrication of stable oil-in-water high internal phase emulsions (HIPEs, ϕ = 0.75). The resulting HIPEs can be easily converted into transparent oleogels with a very high oil loading (99.7%) through oven drying (70 °C). The jelly-like oleogels exhibit weak elastic, shear thinning behavior, good thixotropic recovery, and thermostabilization properties, which might be provided by the percolating 3D network of QS fibrils in the oil phase. We spatially tuned the color performance of the HIPEs and subsequent oleogels by locating the compositions of food colorants in different sections of their hierarchal architecture. The design and construction of hierarchical HIPEs and oleogels provide a promising new route for multitask functional delivery applications in various fields including food, cosmetics, and medical applications.

•Surfactant-free ZCCPEs were formed via a facile approach.•Meso-scale ZCCPs with high surface charges were confirmed as effective Pickering emulsifiers.•Meso-scale hybrid interfacial architectures were visualized for the ZCCPEs.•Stable gels were obtained from the ZCCPEs by a facile one-step freeze-drying process.•ZCCPEs possessed high physical, chemical and microbial stability.Herein, we reported a facile method to fabricate ultra-stable, surfactant- and antimicrobial-free Pickering emulsions by designing and modulating emulsions’ interfaces via zein/chitosan colloid particles (ZCCPs). Highly charged ZCCPs with neutral wettability were produced by a facile anti-solvent procedure. The ZCCPs were shown to be effective Pickering emulsifiers because the emulsions formed were highly resistant to coalescence over a 9-month storage period. The ZCCPs were adsorbed irreversibly at the interface during emulsification, forming a hybrid network framework in which zein particles were embedded within the chitosan network, yielding ultra-stable food-grade zein/chitosan colloid particles stabilized Pickering emulsions (ZCCPEs). Moreover, stable surfactant-free oil gels were obtained by a one-step freeze-drying process of the precursor ZCCPEs. This distinctive interfacial architecture accounted for the favourable physical performance, and potentially oxidative and microbial stability of the emulsions and/or oil gels. This work opens up a promising route via a food-grade Pickering emulsion-template approach to transform liquid oil into solid-like fats with zero trans-fat formation.

•High oil-in-glycerol (O/g) emulgels stabilized by zein in continuous glycerol were formulated.•Zein-based emulgels fortified with β-carotene were fabricated.•β-Carotene degradation decreases and retard oil oxidation during storage of O/G emulgels.•Antioxidant emulgels enriched with β-carotene as margarine alternative used for cake product.Structuring edible oils into solid lipids without saturated and trans fats has attracted increasing interest due to the benefits for human health and promises potential as novel delivery systems for lipophilic bioactive ingredients. The study shows that a zein stabilized high (ϕ = 0.6) oil-in-glycerol (O/G) emulgels enriched with β-carotene was performed, by a facile one-step homogenization. Rheological measurements and morphologies observations indicated that increasing β-carotene resulted in a progressive strengthening of gel-like network and improving their spreadability in the O/G emulgels stabilized by zein, which was closely related to the hydrophobic interaction of zein and β-carotene. The formation of emulgels significantly enhanced the UV photo-stability of β-carotene, and more than 88% of β-carotene was retained in 64 h storage under UV exposure, and consequently retarded oil oxidation while storage. Further, cakes prepared using zein-based O/G emulgels as a margarine alternative showed comparable functionalities (texture and sensory attributes) to the standard cake.

In this study, a detailed investigation into the behavior of foams stabilized by mixtures of zein/TA colloidal particles (ZTP) with a conventional anion surfactant (sodium dodecyl sulfate, SDS) has been made. Foams stabilized by either particles or surfactants alone break down completely within one day at all concentrations tested in the present study. However, ZTP can be induced to form fractal clusters in the presence of a surfactant. In mixed particle–surfactant systems, a synergism occurs with respect to foam properties, since the fractal clusters can be used as building blocks with reaction activity to form stable foams with an orderly interfacial architecture. The formability of ZTP–SDS mixtures increases with the increase of SDS concentration. However, the foam stability increases to a maximum at 0.6 mM SDS followed by a decrease at higher SDS concentrations. In addition, the presence of SDS increases the surface tension decay rate and dilatational modulus, but it seems that their changes are not directly proportional to the SDS concentration. This study indicates that particle–surfactant mixtures can be a potential strategy to modify the particle surface properties and therefore improve foam properties, facilitating the application of zein-based particles in the food and cosmetic industry.

An alkaline isoform of the PR-5 protein (designated GmOLPc) has been purified from soybean hulls and identified by MALDI-TOF/TOF-MS. GmOLPc effectively inhibited in vitro the growth of Phytophthora soja spore and Pseudomonas syringae pv glycinea. The antimicrobial activity of GmOLPc should be mainly ascribed to its high binding affinity with vesicles composed of DPPG, (1,3)-β-d-glucans, and weak endo-(1,3)-β-d-glucanase activity. From the 3D models, predicted by the homology modeling, GmOLPc contains an extended negatively charged cleft. The cleft was proved to be a prerequisite for endo-(1,3)-β-d-glucanase activity. Molecular docking revealed that the positioning of linear (1,3)-β-d-glucans in the cleft of GmOLPc allowed an interaction with Glu83 and Asp101 that were responsible for the hydrolytic cleavage of glucans. Interactions of GmOLPc with model membranes indicated that GmOLPc possesses good surface activity which could contribute to its antimicrobial activity, as proved by the behavior of perturbing the integrity of membranes through surface hydrophobic amino acid residues (Phe89 and Phe94).

The aims of this work were to construct corn protein hydrolysate (CPH)-based curcumin nanoparticles (Cur NPs) and to compare the colloidal stability, bioaccessibility and antioxidant activity of the Cur NPs stabilized CPH and sodium caseinate (NaCas) respectively. The results indicated that Cur solubility could be considerably improved after the Cur NPs fabrication. The spectroscopy results demonstrated that the solubilization of Cur should be attributed to its complexation with CPH or NaCas. The Cur NPs exhibited good colloidal stability after 1 week’s storage but showed smaller (40 nm) size in CPH than in NaCas (100 nm). After lyophilization, the Cur NPs powders showed good rehydration properties and chemical stability, and compared with NaCas, the size of Cur NPs stabilized by CPH was still smaller. Additionally, the Cur NPs exhibited higher chemical stability against the temperature compared with free Cur, and the CPH could protect Cur from degradation more efficiently. Comparing with NaCas, the Cur NPs stabilized by CPH exhibited better bioaccessibility and antioxidant activity. This study demonstrated that CPH may be better than NaCas in Cur NPs fabrication and it opens up the possibility of using hydrophobic protein hydrolysate to construct the NPs delivery system.

In this paper, we developed amphiphilic zein hydrolysate (ZH) as a novel delivery vehicle, which could be used for preparing curcumin (Cur) nanocomplexes. These ZH–Cur nanocomplexes exhibited spherical morphology with a monodisperse size distribution (<50 nm), and the dispersion was transparent, which could have a great application potential in nutraceutical-fortified food and clear beverages. The water solubility of curcumin was considerably enhanced by the nanocomplexation above 8200-fold (vs. free curcumin in water). The good colloidal and storage stability of ZH–Cur nanocomplexes was greatly improved, and more than 60% of curcumin was retained in 72 h storage under ambient conditions. These phenomena appeared to be attributable to the fact that amphiphilic ZH displayed self-assembly properties in water solution and strong interfacial activity at the oil–water interface, as confirmed by micelle formation and dynamic interfacial adsorption respectively. Fluorescence titration and FTIR results indicated the existence of strong hydrophobic interactions between ZH and Cur, which was responsible for the complexation.

Lipid peroxidation in oil-in-water (o/w) emulsions leads to rancidity and carcinogen formation. This work attempted to protect lipid droplets of emulsions from peroxidation via manipulation of the emulsions’ interface framework using dual-function zein/CH complex particles (ZCPs). ZCP with intermediate wettability was fabricated via a simple antisolvent approach. Pickering emulsions were produced via a simple and inexpensive shear-induced emulsification technique. ZCP was irreversibly anchored at the oil–water interface to form particle-based network architecture therein, producing ultrastable o/w Pickering emulsions (ZCPEs). ZCPE was not labile to lipid oxidation, evidenced by low lipid hydroperoxides and malondialdehyde levels in the emulsions after thermally accelerated storage. The targeted accumulation of curcumin, a model antioxidant, at the interface was achieved using the ZCP as interfacial vehicle, forming antioxidant shells around dispersed droplets. The oxidative stability of ZCPEs was further improved. Interestingly, no detectable hexanal peak appeared in headspace gas chromatography of the Pickering emulsions. The novel interfacial architecture via the combination of steric hindrance from ZCP-based membrane and interfacial cargo of curcumin endowed the emulsions with favorable oxidative stability. This study opens a promising pathway for producing antioxidant emulsions via the combination of Pickering stabilization mechanism and interfacial delivery of antioxidant.

The application of food-grade delivery systems for the encapsulation, protection and controlled release of bioactive food ingredients have recently gained increasing interest in the research fields of functional foods and pharmaceutics. Plant proteins (mainly soy proteins, zein and wheat gliadins), which are widely available and environmentally economic compared to animal derived proteins, can be made into various delivery platforms, such as micro- and nanoparticles, fibers, films and hydrogels. In this paper, we review the recent progress in the preparation of food-grade delivery systems based on plant proteins for bioactive ingredients, and highlight some of the challenges and directions that will be the focus of future research. The preparation and application of bifunctional particles, which were able to deliver the bioactives to oil/water interface and stabilize the interface, are also described, providing a novel perspective for the design of plant protein-based delivery system.

Food-grade colloidal particles and complexes, which are formed via modulation of the noncovalent interactions between macromolecules and natural small molecules, can be developed as novel functional ingredients in a safe and sustainable way. For this study was prepared a novel zein/tannic acid (TA) complex colloidal particle (ZTP) based on the hydrogen-bonding interaction between zein and TA in aqueous ethanol solution by using a simple antisolvent approach. Pickering emulsion gels with high oil volume fraction (φoil > 50%) were successfully fabricated via one-step homogenization. Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements, which were used to characterize the structure of zein/TA complexes in ethanol solution, clearly showed that TA binding generated a conformational change of zein without altering their supramolecular structure at pH 5.0 and intermediate TA concentrations. Consequently, the resultant ZTP had tuned near neutral wettability (θow ∼ 86°) and enhanced interfacial reactivity, but without significantly decreased surface charge. These allowed the ZTP to stabilize the oil droplets and further triggered cross-linking to form a continuous network among and around the oil droplets and protein particles, leading to the formation of stable Pickering emulsion gels. Layer-by-layer (LbL) interfacial architecture on the oil–water surface of the droplets was observed, which implied a possibility to fabricate hierarchical interface microstructure via modulation of the noncovalent interaction between hydrophobic protein and natural polyphenol.

•The water solubility of RES was enhanced by complexation with SPI.•Heat treatment favoured the formation and antioxidant activity of SPI–RES complex.•The emulsions stabilized by SPI–RES complex showed an improved oxidative stability.•The improving effect could be mainly due to the accumulation of RES at the interface.This work was to evaluate the potential of soy protein isolate (SPI)–resveratrol (RES) complex as an emulsifier to improve the effectiveness of RES as a natural antioxidant in corn oil-in-water emulsions. The physical properties and oxidative stability of emulsions stabilized by the native SPI–RES and heated SPI–RES complexes were evaluated. The water solubility of RES was enhanced by complexation with SPI, which was mainly driven by hydrophobic interactions. Heat treatment favoured the formation of the SPI–RES complex and endowed it with a higher antioxidant activity. Furthermore, the emulsions stabilized by the SPI–RES complexes showed an increased oxidative stability with reduced lipid hydroperoxides and volatile hexanal. This improving effect could be attributed to the targeted accumulation of RES at the oil–water interface accompanied by the adsorption of SPI, as evidenced by the high interfacial RES concentration. These findings show that the soy protein–polyphenol complex exhibited a good potential to act as an efficient emulsifier to improve the oxidative stability of emulsions.

This paper describes the successful preparation of a protein-based Pickering emulsion, with superior stability against both coalesence and creaming, through a novel strategy of facilitating the formation of protein particles and small molecular weight surfactant complexes; these complexes are able to overcome multiple challenges including limited solubility, poor diffusive mobility, and low interfacial loading. Soluble complexes of water-insoluble corn protein, zein colloidal particles, and surfactant sodium stearate (SS) were fabricated by simple ultrasonication. Gel trapping technology combined with SEM was applied to characterize the adsorbed particles monolayer at the oil–water interface; results revealed an enhanced adsorption and targeted accumulation of zein particles at the interface with the increase of SS concentration. Partial unfolding of zein particles modified by SS above its critical complexation concentration triggered the aggregation and close packing of particles at the oil–water interface and endowed a steric barrier against the coalescence of oil droplets. Moreover, protein-based oil gels without oil leakage were obtained by one-step freeze-drying of the zein-stabilized Pickering emulsions, which could be developed to a viable strategy for structuring liquid oils into semisolid fats without the use of saturated or trans fats.

Amphiphilic graft copolymers were prepared from β-conglycinin–dextran conjugates hydrolyzed by trypsin at a degree of hydrolysis (DH) of 2.2%. Nanoparticles were prepared from β-conglycinin, β-conglycinin–dextran conjugates (CDC), and amphiphilic hydrolysates of β-conglycinin–dextran conjugates at DH 2.2% (CDCH) by a desolvation method. All of the nanoparticle samples exhibited spherical structures, as evidenced by dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering. The nanoparticles prepared from amphiphilic hydrolysates of β-conglycinin–dextran conjugates at DH 2.2% (CDCHN) exhibited higher interfacial pressure and dilatational modulus after long-term absorption at the oil–water interface compared with nanoparticles prepared from β-conglycinin (CN) and β-conglycinin–dextran conjugates (CDCN). This might be mainly associated with the higher surface hydrophobicity of CDCHN, which enhanced adsorption and intermolecular interactions of nanoparticles in the adsorbed layer.

The adsorption of the mixtures of soy glycinin (11S) with a biosurfactant stevioside (STE) at the air–water interface was studied to understand its relation with foaming properties. A combination of several techniques such as dynamic surface tension, dilatational rheology, fluorescence spectroscopy, and isothermal titration calorimetry (ITC) was used. In the presence of intermediate STE concentrations (0.25–0.5%), the weak binding of STE with 11S in bulk occurred by hydrophobic interactions, which could induce conformational changes of 11S, as evidenced by fluorescence and ITC. Accordingly, the strong synergy in reducing surface tension and the plateau in surface elasticity for mixed 11S–STE layers formed from the weakly interacting mixtures were clearly observed. This effect could be explained by the complexation with STE, which might facilitate the partial dissociation and further unfolding of 11S upon adsorption, thus enhancing the protein–protein and protein–STE interfacial interactions. These surface properties were positively reflected in foams produced by the weakly interacting system, which exhibited good foaming capacity and considerable stability probably due to better response to external stresses. However, at high STE concentrations (1–2%), as a consequence of the interface dominated by STE due to the preferential adsorption of STE molecules, the surface elasticity of layers dramatically decreased, and the resultant foams became less stable.

Soy lipophilic protein nanoparticles (LPP), which present a novel delivery vehicle for conjugated linoleic acid (CLA), were fabricated by ultrasonication of the soy lipophilic protein (LP), which exhibits unique characteristics including a high loading capacity, oxidation protection and a sustained releasing profile in vitro for CLA. The CLA-loaded LPP exhibited a mean diameter of 170 ± 0.63 nm and a loading capacity of 26.3 ± 0.40% (w/w). A coating of sodium caseinate (SC) on the surface improved the colloidal stability of the CLA-loaded LPP. This encapsulation conferred protection against the oxidation of CLA, by which the head space-oxygen consumption and hydrogen peroxide value were obviously decreased in comparison with the SC-encapsulated CLA and CLA alone. The delivery system enables a sustained releasing profile of CLA in a simulated gastrointestinal tract (GIT). These findings illustrate that the LPP could act as an effective delivery device for CLA, which could provide oxidation stability and a sustained release property.

To improve the gel strength, we attempt to introduce the microcomposite concept into the food gel system. A stable positively charged chitin microfibers (CMFs) suspension was fabricated by a facile microfluidizer approach without changing its chemical structure. The obtained CMFs bearing width of about 0.5–5 μm and length of more than 500 μm were then developed in a transglutaminase cross-linked β-conglycinin (7S) gel. The morphological and rheological characterizations of the 7S-CMF composited gels were done as a function of the protein and CMFs concentrations. Results showed that the presence of the CMFs network improved the gel strength significantly. This effect was CMFs content dependent and was related to the formation of a sponge-like porous microstructure. We inferred that the CMFs provided an initial framework for gel formation and added structural rigidity to the protein gel. The role of protein was to participate in network development as an electrostatic coating and gelation component.

This work attempted to develop novel high barrier zein/SC nanoparticle (ZP)-stabilized emulsion films through microfluidic emulsification (ZPE films) or in combination with solvent (ethyl acetate) evaporation techniques (ZPE-EA films). Some physical properties, including tensile and optical properties, water vapor permeability (WVP), and surface hydrophobicity, as well as the microstructure of ZP-stabilized emulsion films were evaluated and compared with SC emulsion (SCE) films. The emulsion/solvent evaporation approach reduced lipid droplets of ZP-stabilized emulsions, and lipid droplets of ZP-stabilized emulsions were similar to or slightly lower than that of SC emulsions. However, ZP- and SC-stabilized emulsion films exhibited a completely different microstructure, nanoscalar lipid droplets were homogeneously distributed in the ZPE film matrix and interpenetrating protein–oil complex networks occurred within ZPE-EA films, whereas SCE films presented a heterogeneous microstructure. The different stabilization mechanisms against creaming or coalescence during film formation accounted for the preceding discrepancy of the microstructures between ZP-and SC-stabilized emulsion films. Interestingly, ZP-stabilized emulsion films exhibited a better water barrier efficiency, and the WVP values were only 40–50% of SCE films. A schematic representation for the formation of ZP-stabilized emulsion films was proposed to relate the physical performance of the films with their microstructure and to elucidate the possible forming mechanism of the films.

To fabricate a soy protein emulsion with good storage stability against microorganisms, we investigated the stability and antimicrobial activity of a β-conglycinin (7S) and chitosan (CS) mixed emulsion at acidic pHs. Results of droplet size and microstructure showed that 7S/CS mixed emulsions were stable at acidic pHs while the 7S emulsion was not. As for the storage test, results showed that the 7S/CS mixed emulsion displayed an significantly (p < 0.05) improved storage stability than the control both under un-inoculated and inoculated conditions at 20 °C because of the presence of chitosan. A well diffusion assay showed that the 7S/CS mixed emulsion provided better inhibition against Escherichia coli and the minimum mixing ratio of the chitosan content, of 0.25 mg mL−1, adequately inhibited the bacteria used in this research. Moreover, the aerobic plate count analysis indicated that the 7S/CS mixed emulsion, compared to the control, effectively inhibited the growth of microorganisms. This inhibition was believed to be independent of the CS/7S mixing ratio. The results in this paper demonstrate that the growth of microorganisms dramatically accelerated the destabilization of the stable 7S emulsion and the fabrication of 7S/CS mixed emulsion could increase the acidic stability and antimicrobial activity in order to extend shelf-life.

To strengthen the effectiveness of resveratrol (RES) as a natural antioxidant in food systems, this work attempted to enhance the water solubility of RES by utilizing the solubilizing properties of stevioside (STE) and investigated the effect of STE-solubilized RES (STE–RES) incorporation on the stability of soy protein isolate (SPI)-based emulsions. The physical properties and oxidative stability of SPI emulsions with STE/STE–RES were evaluated. The water solubility of RES increased with the increase of STE concentration up to its critical micelle concentration, suggesting the solubilization of hydrophobic RES in STE self-assembled micelles. STE micelles competitively adsorbed at the oil–water interface with SPI, forming a mixed SPI and STE interfacial layer, thus resulting in a decrease in particle size and evident enhancement in the physical stability of SPI-based emulsions. After the incorporation of STE–RES, SPI emulsions showed an enhanced oxidative stability with reduced lipid hydroperoxides and volatile hexanal. This improvement was believed to be mainly attributed to the targeted migration of RES to the interface during the adsorption of the STE–RES complex, as evidenced by high interfacial accumulation of RES.

A lipophilic protein nanoparticle (LPP) was fabricated by ultrasonication of the soy lipophilic protein (LP), which contains hydrophobic proteins and phospholipids. This LPP (Rh = 136 ± 0.8 nm, ζ-potential = −20 mV, pH 7.0) had an improved dispersibility and acted as an emulsifier. The oil/water (O/W) emulsion stabilized by this LPP exhibited superior physical stability over long-term storage (8 weeks), during a stress storage test (200 mM NaCl addition and heating at 90 °C), and in the presence of Tween 20 (1.0–4.0 wt %), in contrast to those emulsions stabilized by β-conglycinin and glycinin. Langmuir–Blodgett method and interface pressure determination revealed that LPP formed rigid and rough granular film at air/water interface. The excellent stability of emulsions stabilized by LPP highlights the synergic effect between hydrophobic proteins and phospholipids. These findings suggest that the complexes of hydrophobic protein aggregates and biosurfactant could form a stable interface which could be developed into a novel strategy to fabricate a stable food emulsion.

The present investigation aimed to expand the knowledge of the in vitro bioaccessibility of fatty acids and tocopherol from natural soybean oil body emulsions stabilized with different concentrations of ι-carrageenan. Several physicochemical parameters including proteolysis of the interfacial layer, interfacial composition, and microstructure were evaluated with regard to their impact on the bioaccessibility of fatty acids and tocopherol. Results from simulated human digestion in vitro indicated that the bioaccessibility of total fatty acids and tocopherol decreased (62.7–8.3 and 59.7–19.4%, respectively) with the increasing concentration of ι-carrageenan. During the in vitro digestion procedure, ι-carrageenan affected physicochemical properties of the emulsions, thereby controlling the release of fatty acids and tocopherol. These results suggested that soybean oil body emulsions stabilized with ι-carrageenan could provide natural emulsions in foods that were digested at a relatively slow rate, the important physiological consequence of which might be increasing satiety.

We evaluated the influence of heat treatment on interfacial properties (adsorption at the oil–water interface and dilatational rheology of interfacial layers) of soy protein isolate. The related structural properties of protein affecting these interfacial behaviors, including protein unfolding and aggregation, surface hydrophobicity, and the state of sulfhydryl group, were also investigated. The structural and interfacial properties of soy protein depended strongly on heating temperature (90 and 120 °C). Heat treatment at 90 °C induced an increase in surface hydrophobicity due to partial unfolding of protein, accompanied by the formation of aggregates linked by disulfide bond, and lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native protein. Contrastingly, heat treatment at 120 °C led to a higher surface activity of the protein and rapid development of intermolecular interactions in the adsorbed layer, as evidenced by a faster increase of surface pressure and dilatational modulus. The interfacial behaviors of this heated protein may be mainly associated with more flexible conformation and high free sulfhydryl group, even if some exposed hydrophobic groups are involved in the formation of aggregates. These results would be useful to better understand the structure dependence of protein interfacial behaviors and to expand utilization of heat-treated protein in the formulation and production of emulsions.

In this work, different thermal aggregation behaviors of soy β-conglycinin and glycinin at pH 7.0 were characterized with size exclusion chromatography and low-angle light scattering. Limited aggregation that grew via the consumption of “monomers” was detected in β-conglycinin, forming soluble aggregates. For glycinin, the association between the aggregates that led to the appearance of insoluble materials was observed. Heated with β-conglycinin, the assembly between the glycinin aggregates was terminated and its solubility was recovered. The structure of the soluble and insoluble aggregates was analyzed by small-angle X-ray scattering and dynamic light scattering. Unlike the β-conglycinin soluble aggregates that possessed limited size and less compact conformation, particles with a denser core and a less dense outer shell were found in the glycinin insoluble aggregates. Evidence is presented to reveal the transition between the soluble and insoluble aggregates and the role of β-conglycinin in the solubilization of the soy protein aggregates during heating.

The objective of this research was to fabricate novel antimicrobial films based on zein colloidal nanoparticles coated with sodium caseinate (SC), an emulsifier/stabilizer. Thymol-loaded zein–SC nanoparticles were prepared using an antisolvent technique, with the average particle size and zeta potential about 200 ± 20 nm and −40 mV, respectively. Zein–SC nanoparticle-based films exhibited higher mechanical resistance and water barrier capacity than the SC films and concomitant good extensibility as compared with zein films. Thymol loadings endowed zein–SC nanoparticle-based films with antimicrobial activity against Escherichia coli and Salmonella as well as DPPH radical scavenging activity. Water vapor permeability, microstructure, mechanical, and controlled release properties of the films were evaluated. The possible relationship between some selected physical properties and microstructure were also discussed. Atomic force microscopy (AFM) analysis indicated that thymol loadings resulted in the emergence phenomena of the nanoparticles to form large particles or packed structure, consisting of clusters of nanoparticles, within the film matrix, in a thymol loading dependent manner. The appearance of large particles or an agglomerate of particles may weaken the compactness of protein network of films and thus impair the water barrier capacity, mechanical resistance, and extensibility of the films. The release kinetics of thymol from nanoparticle-based films can be described as a two-step biphasic process, that is, an initial burst effect followed by subsequent slower release, and zein–SC nanoparticles within the films matrices gave them the ability to sustain the release of thymol. In addition, a schematic illustration of the formation pathway of zein–SC nanoparticle-based films with or without thymol was proposed to illuminate the possible relationship between some selected physical properties and the microstructure of the films.

The amyloid-like fibrillation of soy β-conglycinin subunits (α, α′, and β) upon heating (0–20 h) at 85 °C and pH 2.0 was characterized using dynamic light scattering, circular dichroism (CD), binding to amyloid dyes (Thioflavin T and Congo red), and atomic force microscopy. The fibrillation of all three subunits was accompanied by progressive polypeptide hydrolysis. The hydrolysis behaviors, fibrillation kinetics, and morphologies of amyloid-like fibrils considerably varied among α, α′, and β subunits. Faster hydrolysis rates and special fragments were observed for the α and α′ subunits compared to the β subunit. However, the order of the fibrillation rate and capacity to form β-sheets was α′ > β > α, as evidenced by CD and Thioflavin T data. Moreover, sequential growth of twisted screw-structure fibrils, leading to macroscopic fibrils with distinct morphological characteristics, was observed for β-conglycinin and individual subunits. The different fibrillation kinetics and morphologies of α, α′, and β subunits appear to be associated with the differences in the amino acid composition and typical sequence of peptides. Besides, the disruption of ordered structure of fibrils occurred upon further heating (6–20 h) due to extensive hydrolysis. These results would suggest that all subunits are involved in the fibrillation of β-conglycinin, following multiple steps including polypeptide hydrolysis, assembly to amyloid structure, and growth into macroscopic fibrils with a fibril shaving process.

The effects of high hydrostatic pressure (HHP) treatment (100–500 MPa) on solubility and structural properties of ethanol (EtOH)-denatured soy β-conglycinin and glycinin were investigated using differential scanning calorimetry, Fourier transform infrared and ultraviolet spectroscopy. HHP treatment above 200 MPa, especially at neutral and alkaline pH as well as low ionic strength, significantly improved the solubility of denatured soy proteins. Structural rearrangements of denatured β-conglycinin subjected to high pressure were confirmed, as evidenced by the increase in enthalpy value (ΔH) and the formation of the ordered supramolecular structure with stronger intramolecular hydrogen bond. HHP treatment (200–400 MPa) caused an increase in surface hydrophobicity (Fmax) of β-conglycinin, partially attributable to the exposure of the Tyr and Phe residues, whereas higher pressure (500 MPa) induced the decrease in Fmax due to hydrophobic rearrangements. The Trp residues in β-conglycinin gradually transferred into a hydrophobic environment, which might further support the finding of structural rearrangements. In contrast, increasing pressure induced the progressive unfolding of denatured glycinin, accompanied by the movement of the Tyr and Phe residues to the molecular surface of protein. These results suggested that EtOH-denatured β-conglycinin and glycinin were involved in different pathways of structural changes during HHP treatment.

Flavor volatiles profiles and some functional properties of soy protein products produced by five different extraction methods were studied. A method, consisting of Ethanol Washing and a Hydrothermal cooking Treatment, was proposed to produce a soy protein product (EWHT). Flavor volatiles profiles, emulsifying ability and whiteness of EWHT were improved in comparison with those of Acid Precipitated soy protein product (AP), soy protein product with Oil-Body Associated proteins and Polar Lipids removed (OBA/PL-less), soy protein product obtained from Countercurrent Extraction (CE) and Oil-Body Associated protein product with Polar Lipids (OBA/PL). The GC-MS and sensory analysis showed that the flavor volatiles content of EWHT was lower than that of the other soy protein products. The results from high performance size exclusion chromatography and dynamic light scattering showed that proteins with larger molecular weights and larger hydrodynamic radii were contained in EWHT, suggesting that EWHT formed soluble larger protein aggregates with a more flexible structure, thus the solubility of EWHT was similar to that of AP, OBA/PL-less and CE. The surface hydrophobicity of EWHT (994.8) was higher than that of the other soy protein products. Therefore the process for preparing EWHT can be an ideal processing method to produce soy protein with good quality relative to flavor and functionality.

Microfluidization followed by density-based separation was employed to extract protein from broken rice by disrupting protein-starch agglomerates. Follow-up enzyme treatments (amylase and glucoamylase) were performed to further improve the purity of the protein-rich fraction. High protein recovery (81.87%) and purity (87.89%) were obtained. The protein composition, solubility, structural properties, and in vitro digestibility of rice proteins prepared by enzyme-assisted microfluidization (EM-RP) and alkaline extraction (AE-RP) were compared. EM-RP was mainly composed of glutelin, which had low solubility and native structure. By contrast, large quantities of prolamin and globulin appeared in the AE-RP except glutelin, leading to the richness of glutamic acid/glutamine, leucine, aromatic and charged amino acids in the AE-RP. Compared to AE-RP, EM-RP showed higher digestibility due to the richness of glutelin (an easy-to-digest protein), as evidenced by higher nitrogen release during pepsin-trypsin digestion. The presence of prolamin (an indigestible protein) in AE-RP decreased protein digestibility although alkaline extraction improved its hydrolysis. These results suggest that enzyme-assisted microfluidization could be an effective technique to non-destructively and selectively extract rice glutelin.Highlights► Microfluidization followed by density-based separation extracts rice protein. ► Carbohydrate-hydrolyzing enzyme treatments improve protein purity. ► Rice glutelin with native structure is non-destructively and selectively obtained. ► Rice glutelin shows better in vitro digestibility than alkali-prepared protein.

•Enzyme-assisted subcritical water efficiently extracts SPI from denatured soy meal.•Maillard reaction and the conversion of isoflavones into aglycones occur.•Aggregated SPI shows more hydrophobic and surface-active characteristics.•Aggregated SPI shows favorable structural and emulsifying properties.Protease prehydrolysis followed by subcritical water (SW) treatment was carried out to extract protein from heat-denatured soy meal. The composition, physicochemical, interfacial and emulsifying properties of soy protein isolate (SPI) were evaluated. A significant increase in extraction yield was observed although protein purity was decreased with prolonged hydrolysis. Due to contaminated β-glucosidase in protease from Aspergillus oryzae, Maillard reaction and the conversion of isoflavone glycosides into aglycones occurred, leading to the enrichment of aglycones in SPI. Compared to native SPI, enzyme-assisted SW-prepared SPI exhibited higher hydrophobic amino acids, surface hydrophobicity, and interfacial adsorption due to protein unfolding, accompanied by the formation of small soluble aggregates. Additionly, remarkable improvements of emulsifying ability and physical stability of emulsion were probably associated with higher surface protein loads. These results could develop a feasible protocol for producing nutrient-enhanced soy proteins with excellent emulsifying properties as novel functional ingredients applied in food industry.

•We developed a novel procedure to prepare zein nanoparticles via FNP.•The effects of FNP processing parameters on the formation of ZP were investigated.•The formation pathway of ZP via FNP with or without NaCas.•FNP process is practical and applicable method to produce ZP in large scale.This study utilized a facile and continuous technique termed Flash NanoPrecipitation (FNP) to produce zein colloidal particles (ZP) without or with sodium caseinate (NaCas) as the stabilizer. The colloidal particle preparations were performed through a self-made Confined Impinge Jet (CIJ) mixer, and compared with traditional antisolvent processes. The influences of FNP processing parameters on the size of zein colloid particles, including flow rates, outlet configurations, solute concentrations and ethanol concentrations, were extensively discussed. The influences of viscous properties, buffering capacity and self-assembly of zein or NaCas on particle size and size distributions were also discussed. Particle sizes of ZP produced by the FNP technique are below 350 nm, even at high zein concentrations (2.5–7.5% w/v). Solvent systems with different ethanol concentrations yielded zein colloid particles with similar size, showing an attractive feature for industrial applications and encapsulating actives with different solubility in ethanol–water binary solvent. This study opens a promising pathway for continuously producing ZP via the FNP procedure.