Stable and pH-sensitive protein nanogels made by self-assembly of heat denatured soy protein

Impact of thermal ultrasound on enzyme inactivation and flavor improvement of sea cucumber hydrolysates

In this study, the effects of the thermal ultrasonic enzyme inactivation process on flavor enhancement in sea cucumber hydrolysates (SCHs) and its impact on the inactivation of neutral proteases (NPs) were investigated. The body wall of the sea cucumber was enzymatically hydrolyzed with NPs. On the one hand, the structure of NPs subjected to different enzyme inactivation methods was analyzed using ζ-potential, particle size, and Fourier transform infrared (FT-IR) spectroscopy. On the other hand, the microstructure and flavor changes of SCHs were examined through scanning electron microscopy, E-nose, and gas chromatography-ion mobility spectrometry (GC-IMS). The results indicated that thermal ultrasound treatment at 60 °C could greatly affect the structure of NPs, thereby achieving enzyme inactivation. Furthermore, this treatment generated more pleasant flavor compounds, such as pentanal and (E)-2-nonenal. Hence, thermal ultrasound treatment could serve as an alternative process to traditional heat inactivation of enzymes for improving the flavor of SCHs.

Exploring changes in aggregation and gel network morphology of soybean protein isolate induced by pH, NaCl, and temperature in view of interactions

The texture of soybean protein-based products is primarily influenced by the aggregation and gel morphology of the protein, which is modulated by manufacturing factors. Interactions involved in protein morphology changes include disulfide bonds, hydrophobic interactions, electrostatic interactions, and hydrogen bonds. Notably, an interaction perspective probably provides a new way to explaining the aggregation and gel morphology, which could help overcome the hurdle of developing a textured product. Based on the interaction perspective, this review provides detailed information and evidence on aggregation, conformational stability, and gel network morphology of soybean protein and its components induced by pH, NaCl, and temperature. pH-induced electrostatic interactions and hydrogen bonds, NaCl-induced electrostatic interactions, and temperature-induced hydrophobic interactions and disulfide linkages are the main motivations responsible for changes in soybean aggregation and gel morphology. By reducing the proportion of strong-interactions, such as disulfide linkages and hydrophobic interactions, and increasing the proportion of weak-interactions, such as electrostatic interactions and hydrogen bonds, the protein total surface area expands, indicating increased conformational stretching and decreased cohesion. This possibly results in reduced hardness and increased toughness of textured proteins. The opposite effect can be observed when the proportion of strong interactions is increased and that of weak interactions is decreased.

Mechanisms of Air Entraining of Proteins in Cementitious Materials

While few prior studies examined the air-entraining properties of proteins in cementitious materials, the underlying mechanisms of proteins' air entraining and the interactions between proteins and cement have not been studied in the past. The significance of this article is to address this knowledge gap by investigating the effect of proteins on relevant factors that affect air entraining in cement paste and establishing an understanding of the mechanism of air entrainment with proteins. These factors include the surface tension of pore solution, protein adsorption on cement particles, cement paste hydrophobization, and flow of fresh paste. Thirteen different proteins were used to investigate the effect of a wide range of protein characteristics on air entraining. Proteins decreased the pore solution surface tension to different degrees. At low concentrations, the adsorption of proteins on cement particles slightly affected the pore solution surface tension. Protein adsorption on cement particles showed a wide range of adsorption isotherms. Proteins generally increased the flow of paste due to electrostatic repulsion between cement particles because of the adsorption of negatively charged proteins on cement particles, as well as the ball-bearing effect of bubbles in fresh paste. The surface hydrophobicity was increased in pastes with proteins. A detailed microcomputed tomography (micro-CT) analysis showed very different air void microstructures in pastes with various proteins. While a relatively strong correlation was observed between air void porosity and surface hydrophobicity, the correlation between air void porosity and the surface tension of pore solution was weak. This indicates that the accumulation of hydrophobized cement particles on the air bubble in the fresh paste, refered to as the Pickering effect, is the main mechanism of air entraining of proteins in the paste. It was shown that a high air void porosity occurs in an intermediate range of flow.

Influence of substrate aggregation state on the enzymatic-induced crosslinking of soy protein isolate

Transglutaminase (TGase) induced-crosslinking of soy protein isolate (SPI) was markedly influenced by the substrate aggregation state. Results showed that appropriate heating significantly accelerated the TGase crosslinking, and the 7S and 11S acidic subunits were more susceptible to the enzyme than the 11S basic proteins. The content of ε-(γ-glutamyl)-lysine isopeptide bonds increased from 4.74 to 8.61 μmol/g protein when the heating intensity was increased from 75 °C for 15 min to 95 °C for 30 min, due to sufficient unfolding of the protein structure. Rheological data indicated that the gel formed from the SPI heated at 95 °C for 30 min exhibited the best properties, with a 60 % increase in the storage modulus compared with the unheated sample. However, excessive heating (95 °C, 60-120 min) caused severe aggregation of SPI and formation of insoluble aggregates, resulting in poor crosslinking efficiency and weaker gel properties.

Improving the properties of whey protein isolate-zein nanogels with novel acidifiers: Re-dispersity, stability and quercetin bioavailability

Low bioavailability of quercetin (Que) reduces its preclinical and clinical benefits. In order to improve Que bioavailability, a novel whey protein isolate (WPI)-zein nanogel was prepared by pH-driven self-assembly and heat-induced gelatinization. The results showed that hydrochloric acid can be substituted by both acetic acid and citric acid during the pH-driven process. After encapsulation, the bioavailability of Que in nanogels (composed of 70 % WPI) induced by different acidifiers increased to 19.89 % (citric acid), 21.65 % (hydrochloric acid) and 24.34 % (acetic acid), respectively. Comparatively, nanogels induced by acetic acid showed higher stability (pH and storage stability), re-dispersibility (75.62 %), Que bioavailability (24.34 %), and antioxidant capacity (36.78 % for DPPH scavenging rates). s improved performance of nanogels. In mechanism, acetic acid significantly balanced different intermolecular forces by weakening "acid-induced denaturation" effect. Moreover, the faster binding of Que and protein as well as higher protein molecular flexibility and randomness (higher ratio of random coil) was also observed in nanogels induced by acetic acid. All of these changes contributed to improve nanogels performances. Overall, WPI-zein nanogels induced by acetic acid might be a safe, efficiency and stable delivery system to improve the bioavailability of hydrophobic active ingredients.

Influence of pH and ionic strength on the physicochemical and structural properties of soybean β-conglycinin subunits in aqueous dispersions

Understanding the impact of pH and ionic strength on the physicochemical and structural properties of soy proteins at subunit level is essential for design and fabrication of many plant-based foods. In this study, soybean β-conglycinin and its subunit fractions αα' and β were dispersed in solutions with different pH values (3.7, 7.6, and 9.0) at low (5 mM NaCl) and high (400 mM NaCl) ionic strengths, respectively. The solubility, rheology, particle size, zeta potential, microstructure, secondary structure, and tertiary structure of the different dispersions were analyzed using a range of analytical methods. The β-conglycinin, αα'- and β-subunits aggregated near the isoelectric point (pH 3.7). Increasing the ionic strength led to the assembly of more homogeneous units. An increase in ionic strength at pH 7.6 and pH 9.0 led to electrostatic screening, which promoted dissociation of the aggregates. The β-subunit showed a greater sensitivity to pH and ionic strength than the αα'-subunits. Based on the evidence from a range of analytical methods, the highly hydrophilic extension region of the αα'-subunits played an important role in determining the stability of the β-conglycinin dispersions under different environmental conditions. Moreover, the N-linked glycans appeared to impact the conformation and aggregation state of the β-conglycinin.

Characterizations of food-derived ellagic acid-Undaria pinnatifida polysaccharides solid dispersion and its benefits on solubility, dispersity and biotransformation of ellagic acid

The current study was aimed to enhance the solubility, dispersibility and biotransformation efficacy of ellagic acid (EA) by preparing food-derived ellagic acid-Undaria pinnatifida polysaccharides solid dispersion (EA/UPP SD). The results demonstrated that the solubility of EA/UPP SD was improved from 0.014 mg/mL to 0.383 mg/mL, and the enhancement was related to converting to a more amorphous state and restraining its self-aggregation during the mechanochemical process. The structure of EA/UPP SDs was mostly maintained by hydrogen bonds and hydrophobic interactions between EA and UPP. Moreover, the result of in vitro anaerobic incubations showed the biotransformation process was improved with EA/UPP SD addition to substrate due to the advance of microbial accessibility in EA dispersion. Altogether, these results indicated that the EA/UPP SDs expanded the application of EA by increasing the solubility and dispersity, and provided a theoretical basis for bioconversion efficiency enhancement.

Fabrication and characterization of succinylated and glycosylated soy protein isolate and its self-assembled nanogel

In this study, we used succinic anhydride (SA) acylation and dextran (DX) glycosylation modified soybean isolate protein (SPI) to develop self-assembled SPI-SA-DX adduct-based nanogels. Degree of modification, SDS-PAGE, and FT-IR studies showed that the amino group of the SPI was replaced by hydrophilic dextran and succinic acid carboxyl groups. Dextran chain and anhydride group attachment to the soybean protein surface enhanced hydrophilicity and spatial site blocking. Modification-induced protein structure unfolding, free sulfhydryl groups to be converted to disulfide bonds, and reduced surface hydrophobicity (H₀). H₀ was lowest at 33,750 ± 1008.29 when SA content = 10 % protein content (SPI-SA₃-DX). The nanometer gel based on SPI-SA₃-DX had the maximum turbidity and clear transparent solution without precipitation. Its particle size and polymer dispersibility index (PDI) were also the smallest, with values of (106.87 ± 4.51) nm and 0.21 ± 0.009, respectively. Transmission electron microscopy showed that nanogels had subspherical shell-core structures. Nanogels were stable under different pH, ionic strength, high temperature, and storage conditions.

Effects of heating rates on the self-assembly behavior and gelling properties of beef myosin

BACKGROUND

Myosin is the most important component of myofibrillar protein, with excellent gelling properties. To date, heating treatment remains the mainstream method for forming gel in meat products, and it has the most extensive application in the field of meat industry. However, at present, there are few reports on the effects of heating rates on myosin self-assembly and aggregation behavior during heating treatment.

RESULTS

The present study aimed to investigate the effects of different heating rates (1, 2, 3 and 5 °C min^-1 ) on the self-assembly behavior, physicochemical, structural and gelling properties of myosin. At the lowest heating rate of 1 °C min^-1 , the myosin gel had a dense microstructure, the highest elastic modulus (G') and water holding capacity compared to higher heating rates (2, 3 and 5 °C min^-1 ). At higher temperatures (40, 45 °C), the surface hydrophobicity, turbidity, particle size distribution and self-assembly behavior of myosin in pre-gelling solutions showed that myosin had sufficient time to denature, underwent full structure unfolding before aggregation at the heating rate of 1°C min^-1 , and formed regular and homogeneous spherical aggregates. Therefore, the myosin gel also had a better three-dimensional network.

CONCLUSION

The heating rates had an important effect on the quality of myosin gels, and had theoretical implications for improving the quality of meat gel products. © 2023 Society of Chemical Industry.

Emerging plant proteins as nanocarriers of bioactive compounds

The high prevalence of chronic illnesses, including cancer, diabetes, obesity, and cardiovascular diseases has become a growing concern for modern society. Recently, various bioactive compounds (bioactives) are shown to have a diversity of health-beneficial impacts on a wide range of disorders. But the application of these bioactives in food and pharmaceutical formulations is limited due to their poor water solubility and low bioaccessibility/bioavailability. Plant proteins are green alternatives for designing biopolymeric nanoparticles as appropriate nanocarriers thanks to their amphiphilic nature compatible with many bioactives and unique functional properties. Recently, emerging plant proteins (EPPs) are employed as nanocarriers for protection and targeted delivery of bioactives and also improving their stability and shelf-life. EPPs could enhance the solubility, stability, and bioavailability of bioactives by different types of delivery systems. In addition, the use of EPPs in combination with other biopolymers like polysaccharides was found to make a favorable wall material for food bioactives. This review article covers the various sources and importance of EPPs along with different encapsulation techniques of bioactives. Characterization of EPPs for encapsulation is also investigated. Furthermore, the focus is on the application of EPPs as nanocarriers for food bioactives.

Optimising Soy and Pea Protein Gelation to Obtain Hydrogels Intended as Precursors of Food-Grade Dried Porous Materials

Dried porous materials based on plant proteins are attracting large attention thanks to their potential use as sustainable food ingredients. Nevertheless, plant proteins present lower gelling properties than animal ones. Plant protein gelling could be improved by optimising gelation conditions by acting on protein concentration, pH, and ionic strength. This work aimed to systematically study the effect of these factors on the gelation behaviour of soy and pea protein isolates. Protein suspensions having different concentrations (10, 15, and 20% w/w), pH (3.0, 4.5, 7.0), and ionic strength (IS, 0.0, 0.6, 1.5 M) were heat-treated (95 °C for 15 min) and characterised for rheological properties and physical stability. Strong hydrogels having an elastic modulus (G') higher than 10³ Pa and able to retain more than 90% water were only obtained from suspensions containing at least 15% soy protein, far from the isoelectric point and at an IS above 0.6 M. By contrast, pea protein gelation was achieved only at a high concentration (20%), and always resulted in weak gels, which showed increasing G' with the increase in pH and IS. Results were rationalised into a map identifying the gelation conditions to modulate the rheological properties of soy and pea protein hydrogels, for their subsequent conversion into xerogels, cryogels, and aerogels.

Improved Light and In Vitro Digestive Stability of Lutein-Loaded Nanoparticles Based on Soy Protein Hydrolysates via Pepsin

In order to improve the water solubility and stability of lutein, soy protein isolates (SPI) and their hydrolysates via pepsin (PSPI) and alcalase (ASPI) were used as nanocarriers for lutein to fabricate the lutein-loaded nanoparticles (LNPS) of SPI, PSPI, and ASPI. The encapsulation properties, light, and in vitro digestive stability of lutein in nanoparticles, and protein-lutein interactions were investigated. Compared with SPI-LNPS and ASPI-LNPS, PSPI-LNPS was characterized by uniform morphology (approximately 115 nm) with a lower polydispersity index (approximately 0.11) and higher lutein loading capacity (17.96 μg/mg protein). In addition, PSPI-LNPS presented the higher lutein retention rate after light exposure (85.05%) and simulated digestion (77.73%) than the unencapsulated lutein and SPI-LNPS. Fluorescence spectroscopy revealed that PSPI had stronger hydrophobic interaction with lutein than SPI, which positively correlated with their beneficial effects on the light and digestive stability of lutein. This study demonstrated that PSPI possessed significant potential for lutein delivery.

New Perspective on Natural Plant Protein-Based Nanocarriers for Bioactive Ingredients Delivery

The health effects of bioactive substances in the human body are affected by several factors, including food processing conditions, storage conditions, light and heat, among others. These factors greatly limit the stability and bioavailability of bioactive substances. These problems can be solved by a novel protein-based nanocarrier technology, which has the excellent potential to enhance solubility, bioavailability, and the controlled release of bioactive substances. In addition, plant protein has the advantages of economy, environmental protection, and high nutrition compared to animal protein. In this review, the preparation, characterization, and application of plant protein-based nanocarriers are summarized. The research deficiency and future prospects of plant protein nanocarriers are emphasized.

Preparation and characterization of soybean protein isolate-dextran conjugate-based nanogels

Soybean protein isolate (SPI)-dextran conjugate-based nanogels were prepared via the Maillard reaction combined with protein self-assembly in this study. The dextran molecular weight (40 kDa), SPI/dextran mass ratio (1:1.75), and incubation time (3.3 d) for preparing SPI-dextran conjugate (SDC) were firstly optimized. The SDC was confirmed by analyzing the changes in protein composition and infrared absorption bands and showed loosened tertiary conformation, reduced surface hydrophobicity, decreased Z-average hydrodynamic diameter (D_h) and zeta potential, and improved emulsifying properties compared to the native SPI. Effects of conjugate concentration, pH, heating temperature, and time on D_h and polydispersity index were also evaluated. The SDC-based nanogels were translucent in aqueous solution and exhibited a spherical core-shell structure with a D_h of ∼104.4 nm and a good stability against thermal treatment, ionic strength, and storage. Results demonstrated the SDC-based nanogels possessed a potential to be used as desirable nanocarriers for encapsulating hydrophobic bioactive compounds.

Efficient reclamation phosphate by alginate-g-BMOF using poly(N-isopropyl acrylamide-co-acrylamide) as coating for temperature-responsive slow-release P-fertilizer

Poly(N-isopropyl acrylamide) and its derived copolymer, as a temperature-responsive material, are widely used in the field of anticancer drug carrier. And it also plays an important role as carrier in slow-release fertilizer in recent years. In this paper, a smart poly(N-isopropyl acrylamide-co-acrylamide)-coated Alg-BMOF (PABMOF) was fabricated in ionic liquids microemulsion ([Bmim]PF₆/TX-100/water) as nano-reactor. The structure and morphology of PABMOF were characterized by FT-IR, XRD, XPS, SEM, TG and BET. The resultant PABMOF was used as a adsorbent for H₂PO₄^- adsorption. The adsorption kinetics, isotherms and mechanism of H₂PO₄^- onto the resultant PABMOF were studied. The adsorption kinetic data was well suitable for pseudo-second-order kinetic model, and adsorption isotherm results demonstrated that the equilibrium data was fitted for Freundlich model. The water-holding and water-retention capacity of soil with TRSRFs addition of 2 wt% were74.3% and 52.13% at 30th day, respectively. Moreover, the release behavior of TRSRFs in water show that the cumulative release rate (C_r%) were 81.4% at 45 °C and 97.6% at 25 °C within 172 h, which displayed the excellent temperature-responsive property. The effect of TRSRFs on the growth of Chinese cabbage was investigated, which was indexed with the germination rate, plant height and root length of the crop.

Characteristics of Pickering emulsions stabilized by tea water-insoluble protein nanoparticles at different pH values

This study aimed to explore the characteristics of Pickering emulsions stabilized by tea water-insoluble protein nanoparticles (TWIPNs) at different pH values. The characteristics of TWIPNs at different pH values were analysed first. The average hydrodynamic diameter of TWIPNs in the suspension was smaller than 400 nm at pH 7-11. TWIPNs at pH 3 could not be used to stabilize Pickering emulsions. The flocculation index (FI) of fresh TWIPN-stabilized Pickering emulsions (TWIPNPEs) at pH 5 was higher than those of TWIPNPEs at pH 7-11 (FI < 5%), indicating that bridging flocculation led to the aggregation of small emulsion droplets. The zeta potential of TWIPNPEs at pH 7-11 did not change after 7 d. In addition, the TWIPNPEs showed gel-like properties under neutral and alkaline conditions. These results will be helpful for broadening the application of TWIPNPEs at different pH values.

Sound methods for the synthesis of nanoparticles from biological molecules

The development of simple, green, reproducible, and scalable approaches for synthesizing nanoparticles from biomolecules is important to advance nanomaterials towards therapeutic applications. Microreactors generated by high frequency ultrasound provide a one pot-platform to alter the physiochemical properties and stability of various types of biomolecules to ultimately generate multifunctional nanoparticles with controlled size and morphology. Herein, recent advancements in the field of nanoparticles fabrication from amino acids, phenolics, peptides and proteins using both high and low frequency ultrasound are reviewed. In particular, the sound driven self-assembly of biomolecules into nanoparticles by using high frequency ultrasound, as an emerging and innovative approach, is discussed in detail.

Influence of Whey Protein Micro-Gel Particles and Whey Protein Micro-Gel Particles-Xanthan Gum Complexes on the Stability of O/W Emulsions

Appropriate pretreatment of proteins and addition of xanthan gum (XG) has the potential to improve the stability of oil-in-water (O/W) emulsions. However, the factors that regulate the enhancement and the mechanism are still not clear, which restricts the realization of improving the emulsion stability by directional design of its structure. Therefore, the effects of whey protein micro-gel particles (WPMPs) and WPMPs-XG complexes on the stability of O/W emulsion were investigated in this article to provide theoretical support. WPMPs with different structures were prepared by pretreatment (controlled high-speed shear treatment of heat-set WPC gels) at pH 3.5–8.5. The impact of initial WPC structure and XG addition on Turbiscan Indexes, mean droplet size and the peroxide values of O/W emulsions was investigated. The results indicate that WPMPs and XG can respectively inhibit droplet coalescence and gravitational separation to improve the physical stability of WPC-stabilized O/W emulsions. The pretreatment significantly enhanced the oxidative stability of WPC-stabilized O/W emulsions. The addition of XG did not necessarily enhance the oxidative stability of O/W emulsions. Whether the oxidative stability of the O/W emulsion with XG is increased or decreased depends on the interface structure of the protein-XG complex. This study has significant implications for the development of novel structures containing lipid phases that are susceptible to oxidation.

Protein-Based Nanohydrogels for Bioactive Delivery

Hydrogels possess a unique three-dimensional, cross-linked network of polymers capable of absorbing large amounts of water and biological fluids without dissolving. Nanohydrogels (NGs) or nanogels are composed of diverse types of polymers of synthetic or natural origin. Their combination is bound by a chemical covalent bond or is physically cross-linked with non-covalent bonds like electrostatic interactions, hydrophobic interactions, and hydrogen bonding. Its remarkable ability to absorb water or other fluids is mainly attributed to hydrophilic groups like hydroxyl, amide, and sulphate, etc. Natural biomolecules such as protein- or peptide-based nanohydrogels are an important category of hydrogels which possess high biocompatibility and metabolic degradability. The preparation of protein nanohydrogels and the subsequent encapsulation process generally involve use of environment friendly solvents and can be fabricated using different proteins, such as fibroins, albumin, collagen, elastin, gelatin, and lipoprotein, etc. involving emulsion, electrospray, and desolvation methods to name a few. Nanohydrogels are excellent biomaterials with broad applications in the areas of regenerative medicine, tissue engineering, and drug delivery due to certain advantages like biodegradability, biocompatibility, tunable mechanical strength, molecular binding abilities, and customizable responses to certain stimuli like ionic concentration, pH, and temperature. The present review aims to provide an insightful analysis of protein/peptide nanohydrogels including their preparation, biophysiochemical aspects, and applications in diverse disciplines like in drug delivery, immunotherapy, intracellular delivery, nutraceutical delivery, cell adhesion, and wound dressing. Naturally occurring structural proteins that are being explored in protein nanohydrogels, along with their unique properties, are also discussed briefly. Further, the review also covers the advantages, limitations, overview of clinical potential, toxicity aspects, stability issues, and future perspectives of protein nanohydrogels.

Preparation of Pickering emulsion based on soy protein isolate-gallic acid with outstanding antioxidation and antimicrobial

This study investigated a novel antioxidant and antimicrobial Pickering emulsion stabilized by soy protein isolate (SPI) and gallic acid (GA) as an excellent protective delivery medium for lipophilic functional food. SPI-GA complex nanoparticles were fabricated by a covalent cross-linking mechanism under alkaline conditions with a small particle size (42.93-24.91 nm) and high zeta potential (26.92-38.58 -mV), which led to improved stability at high GA concentrations. Without the addition of preservatives, it was found that SPI-GA complex nanoparticles have a certain antimicrobial ability. Using these nanoparticles as the only stabilizers, outstanding antioxidant and antimicrobial Pickering emulsions could be easily prepared, and they had a small droplet size (948.09-457.82 nm), great stability and inhibited lipid peroxidation and antibacterial ability. Oxidation and microbial protection proceeded in a GA concentration-dependent manner. This study provides a novel way to prepare functionalized Pickering emulsions as delivery media for functional lipophilic raw materials.

Nano-architectural assembly of soy proteins: A promising strategy to fabricate nutraceutical nanovehicles

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.

Complexation of β-lactoglobulin with gum arabic: Effect of heat treatment and enhanced encapsulation efficiency

Heat treatment is widely used in food industry. Proteins and polysaccharides as important natural polymers in food, under heat treatment, the interactions between them could mediate the conformation and functional properties of proteins. Thermally induced β-lactoglobulin-gum arabic complexes (β-Lg-GA) were fabricated, and the effect of heat treatment on physicochemical properties of the complexes was systematically investigated. The average particle size of β-Lg-GA complexes decreased with temperature increased, at 85°C, a smaller size of 273 nm was obtained. A saturated adsorption of GA was found when mass ratio of β-Lg/GA was <1:2. At pH = 4.2-7.0, electrostatic attraction between β-Lg and GA was low and a fairly constant turbidity was observed, the formed composite particles had good stability to the pH value. Through UV, fluorescence, and FTIR spectroscopy, it was found that formation of the nanoparticles relied on thermal denaturation and aggregation of protein, the electrostatic, hydrophobic, and hydrogen bonding interactions between β-Lg and GA were also important. Scanning electron microscope further indicated β-Lg and GA had good compatibility, and the complexes had a spherical core-shell structure at molecular level. In addition, these prepared natural nanoparticles by heat treatment show significantly higher encapsulation efficiency for (-)-epigallocatechin-3-gallate (EGCG) than that of unheated, thus could be used as a promising carrier for biologically active substances.

Reinjection flow field-flow fractionation method for nanoparticle quantitative analysis in unknown and complex samples

An analytical challenge that arises in environmental and food analysis is to quantify heterogeneous nanoparticles especially in polydisperse and complex samples. The method stated herein based on the reinjection asymmetrical flow field-flow fractionation (AF4 × AF4) coupled with inductively coupled plasma-mass spectrometer (ICP-MS) and statistical deconvolution allowed for identifying the molecular weight (Mw) and selenium abundance of the low Mw protein fractions (ca. < 132 kDa) in an unknown and complex sample (e.g., selenium-rich soybean protein isolates (Se-SPI)). A non-linear decay crossflow program was also developed to get better resolution and shorter elution time for both low and high Mw components. The concept of the reinjection method was based on the excellent ability for reducing sample complexity regarding the size fractionation, and peak reproducibility under the identical conditions of AF4 system. The standard protein mixture was used as a proof-of-principle sample. The results showed the underlying peaks predicted by the reinjection method were agreed with the separation result using the standard mixture (the relative standard deviation of peak locations < 1%), which indicated the reinjection method could provide an accurate assessment of the underlying peak number and location, and was promising to minimize the overfitting problem for statistic deconvolution. Interestingly, significant differences of Se abundance in protein fractions were observed in the low Mw range for Se-SPI, ranging from 0.28 to 1.66 cps/V with the Mw ranging from 13.75 kDa to 104.17 kDa, which indicated significant differences in the ability of binding Se for these selenium-rich proteins in Se-SPI.

Amphiphilic mPEG-Modified Oligo-Phenylalanine Nanoparticles Chemoenzymatically Synthesized via Papain

Amphiphilic mPEG-modified peptide nanoparticles were developed from oligo-phenylalanine (OPhe) nanoparticles (NPs) synthesized via papain. Tyndall effects indicate that OPhe NPs are amphiphobic. Addition of protein perturbants, sodium dodecyl sulfate (SDS), and urea, in the dispersion solution of OPhe NPs can significantly reduce the R _h,m value of NPs, from approximately 749.2 nm to about 200 nm. Therefore, the hydrophobic interaction and hydrogen bonding play major roles in maintaining the aggregation of OPhe NPs. Using the "grafting to" method, the methoxypolyethylene-modified OPhe NPs (mPEG-g-OPhe NPs) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H NMR, electrospray ionization mass spectrometry (ESI-MS), and dynamic light scattering (DLS). The attenuated total reflectance (ATR) spectrum of OPhe NPs and mPEG-g-OPhe NPs demonstrate that the secondary structures of these NPs are mainly β-type. mPEG-g-OPhe NPs can self-aggregate into spherical micelles both in water and cyclohexane. Increasing the chain length of the mPEG moiety, the critical micellar concentrations of mPEG-g-OPhe NPs increased in water but decreased in cyclohexane. The light stability, thermal stability, hydrolysis stability, and encapsulation stability of curcumin were significantly promoted by encapsulation in the micelles formed by mPEG-g-OPhe NPs. The protective effects regularly varied with the variations in the mPEG chain length of mPEG-g-OPhe NPs.

Deciphering the Structural Network That Confers Stability to High Internal Phase Pickering Emulsions by Cross-Linked Soy Protein Microgels and Their In Vitro Digestion Profiles

High internal phase Pickering emulsions (HIPPEs) stabilized by food-grade particles have received much attention in recent years. However, the stabilizing mechanism (e.g., structural network) in the continuous phase of HIPPEs stabilized by proteins is not well understood. In this work, we deciphered the stabilizing mechanisms that confer stability to HIPPEs produced from sunflower oil and soy protein microgels (SPMs). HIPPEs were fabricated at the protein concentrations of 1.50-2.00 wt % and oil volume fraction of 0.78-0.82. The cryo-scanning electron microscopy (cryo-SEM) observations indicated that there were two possible stabilizing mechanisms for HIPPEs at the protein concentrations of 1.50-2.00 wt %: the first is a stabilization provided by the shared monolayer of SPMs (at a protein concentration of 1.50%), and the other is stabilization provided by the distinct monolayer of SPMs (at protein concentrations of 1.75 and 2.00 wt %). The latter protein concentration created a thick network, formed by interacting SPMs, which trapped oil droplets. Results also confirmed that HIPPEs have an open-cell porous structure, forming a sponge-like morphology, where the internal phase was located. This study also investigated the digestibility of HIPPEs, suggesting a slower free fatty acid-releasing profile in in vitro intestinal digestion.

Adsorption layer formation in dispersions of protein aggregates

The review discusses recent results on the adsorption of amyloid fibrils and protein microgels at liquid/fluid interfaces. The application of the shear and dilational surface rheology, atomic force microscopy and passive particle probe tracking allowed for elucidating characteristic features of the protein aggregate adsorption while some proposed hypothesis still must be examined by special methods for structural characterization. Although the distinctions of the shear surface properties of dispersions of protein aggregates from the properties of native protein solutions are higher than the corresponding distinctions of the dilational surface properties, the latter ones give a possibility to obtain new information on the formation of fibril aggregates at the water/air interface. Only the adsorption of BLG microgels and fibrils was studied in some details. The kinetic dependencies of the dynamic surface tension and dilational surface elasticity for aqueous dispersions of protein globules, protein microgels and purified fibrils are similar if the system does not contain flexible macromolecules or flexible protein fragments. In the opposite case the kinetic dependencies of the dynamic surface elasticity can be non-monotonic. The solution pH influences strongly the dynamic surface properties of the dispersions of protein aggregates indicating that the adsorption kinetics is controlled by an electrostatic adsorption barrier if the pH deviates from the isoelectric point. A special section of the review considers the possibility to apply kinetic models of nanoparticle adsorption to the adsorption of protein aggregates.