Structure remodeling of soy protein-derived amyloid fibrils mediated by epigallocatechin-3-gallate

Complexes of soybean protein fibrils and chlorogenic acid: Interaction mechanism and antibacterial activity

This study explored the mechanism of interaction between chlorogenic acid (CA) and protein fibrils (PF) as well as the effects of varying the CA/PF concentration ratio on antibacterial activity. Analysis of various parameters, such as ζ-potential, thioflavin T fluorescence intensity, surface hydrophobicity, and free sulfhydryl groups, revealed that the interaction between PF and CA altered the structure of PF. Fluorescence analysis revealed that hydrogen bonding and hydrophobic interactions were the primary interaction forces causing conformational rearrangement, resulting in a shorter, more flexible, and thicker fibril structure, as observed through transmission electron microscopy. Fourier-transform infrared spectroscopy, small-angle X-ray scattering, and X-ray diffraction analyses revealed that the characteristic fibril structure was destroyed when the CA/PF ratio exceeded 0.05. Notably, the CA-PF complexes inhibited the growth of Escherichia coli and Staphylococcus aureus and also exhibited antioxidant activity. Overall, this study expands the application prospects of CA and PF in the food industry.

Synthesis and characterization of ion-induced sodium alginate/soy protein isolate microgels for the controlled release

In this study, sodium alginate/ soy protein isolate (SPI) microgels cross-linked by various divalent cations including Cu2+, Ba2+, Ca2+, and Zn2+ were fabricated. Cryo-scanning electron microscopy observations revealed distinctive structural variations among the microgels. In the context of gastric pH conditions, the degree of shrinkage of the microgels followed the sequence of Ca2+ > Ba2+ > Cu2+ > Zn2+. Meanwhile, under intestinal pH conditions, the degree of swelling was ranked as Zn2+ > Ca2+ > Ba2+ > Cu2+. The impact of these variations was investigated through in vitro digestion studies, revealing that all microgels successfully delayed the release of β-carotene within the stomach. Within the simulated intestinal fluid, the microgel cross-linked with Zn2+ exhibited an initial burst release, while those cross-linked with Cu2+, Ba2+, or Ca2+ displayed a sustained release pattern. This research underscores the potential of sodium alginate/SPI microgels cross-linked with different divalent cations as efficient controlled-release delivery systems.

Remodeling mechanism of gel network structure of soy protein isolate amyloid fibrils mediated by cellulose nanocrystals

The differences in the gelling properties of soy protein isolate (SPI) and soy protein isolate amyloid fibrils (SAFs) as well as the role of cellulose nanocrystals (CNC) in regulating their gel behaviors were investigated in this study. The binding of CNC to β-conglycinin (7S), glycinin (11S), and SAFs was predominantly driven by non-covalent interactions. CNC addition reduced the particle size, turbidity, subunit segments, and crystallinity of SPI and SAFs, promoted the conversion of α-helix to β-sheet, improved the thermal stability, exposed more tyrosine and tryptophan residues, and enhanced the intermolecular interactions. A more regular and ordered lamellar network structure was formed in the SAFs-CNC composite gel, which could be conducive to the improvement of gel quality. This study would provide theoretical reference for the understanding of the regulatory mechanism of protein amyloid fibrils gelation as well as the high-value utilization of SAFs-CNC complex as a functional protein-based material or food ingredient in food field.

Lysozyme amyloid fibril-chitosan double network hydrogel: Preparation, characterization, and application on inhibition of Nε-(carboxyethyl)lysine

Nε-(carboxyethyl)lysine (CML), a typical advanced glycosylation end product produced during the processing of meat under high temperature, poses health risks. Active substances like polyphenols are known to inhibit the formation of harmful products during the processing of food. In this study, our objective was to prepare a double network hydrogel (DN) loaded with gallic acid using amyloid fibers and chitosan as a rigid and flexible network, respectively. The network as well as the interactions between the two networks were observed and analyzed. Chitosan concentration was the key factor regulating the structure and properties of the DN. At a chitosan concentration of 0.7%wt, the structure of DN became dense and its mechanical properties were improved, with the loading capacity and loading efficiency being increased by 143.79 % and 128.21 %, compared with those of amyloid fibril alone. Furthermore, the digestibility of gallic acid in simulated intestinal fluid was increased by 215.10 %. Moreover, adding DN to the beef patties effectively inhibited the formation of CML in a dose-response dependent manner. Addition of 3 wt% DN resulted in the inhibitory rate of CML in roast beef patties reaching a high 73.09 %. The quality and palatability of beef patties were improved. These findings suggest that DN shows great potential as an application that may be utilized to deliver active substances aimed at inhibiting CML in the meat processing industry.

Gallic acid-functionalized soy protein-based multiple cross-linked hydrogel: Mechanism analysis, physicochemical properties, and digestive characteristics

Herein, carbodiimide hydrochloride/N-hydroxysuccinimide was used to mediate the grafting of gallic acid (GA) (0.005, 0.0015, and 0.025 wt%) with soybean protein isolate (SPI) in the preparation of SPI-GA conjugates and hydrogels. The modified materials were primarily joined via the CN bonds and exhibited excellent antioxidant properties. In addition, spectral analysis revealed that the grafting of GA increased the flexibility of the SPI structure. The SPI-GA hydrogel is fabricated through covalent/non-covalent cross-linking mechanisms, including Schiff base, Michael addition, and hydrogen bonding. Furthermore, the microstructure, rheological properties, thermal stability, and textural properties of the hydrogel were affected by the amount of GA grafted. The SPI-GA hydrogel exhibited the best performance when the amount of GA graft was 0.015 wt%. Furthermore, the tightly cross-linked structure of SPI-GA prevented premature degradation of the protein by pepsin. In conclusion, these capabilities provide numerous possibilities for the development of multifunctional and active substance delivery carriers.

Recent advance in modification strategies and applications of soy protein gel properties

Soy protein gel can be developed into a variety of products, ranging from traditional food (e.g., tofu) to newly developed food (e.g., soy yogurt and meat analog). So far, efforts are still needed to be made on modifying the gel properties of soy protein for improving its sensory properties as animal protein-based food substitutes. Furthermore, there is always a need to regulate its gel properties for designing novel and tailored products of soy protein gels due to the fast-growing plant protein-based product market. This review gave an emphasis on the latest modification strategies and applications of gel properties of soy protein. The modifying methods of soy protein gel properties were reviewed from an aspect of composition or processing. Compositional modification included changing protein composition and gelling conditions and using additives, whereas processing strategies can be achieved through physical, chemical, and enzymatic treatments. Several compositional modification and processing strategies have been both proven to alter the gel properties of soy protein effectively. So far, soy protein gel has been applied in the field of food and biomedicine. In the future, more mechanistic studies on the modification methods are still needed to facilitate the full application of soy protein gel.

Formation, structure and functional characteristics of amyloid fibrils formed based on soy protein isolates

Food protein-derived amyloid fibrils possess great untapped potential applications in food and other biomaterials. The objective of this report was to investigate the formation mechanism, structure and functional characterization of soy protein amyloid fibrils (SPF) through hydrolysis and heating (pH 2.0, 85 °C, 0-24 h) of soy protein isolate (SPI). Fibrillation growth analysis indicated polypeptide hydrolysis upon hydrolytic heating, and the amyloid fibrils were basically formed 8 h later. The microstructure of SPF was monitored by transmission electron microscopy and scanning electron microscopy, exhibiting change from an irregular spherical structure to a coiled, intertwined thread-like polymer. The secondary structures of SPI all changed drastically during the fibrillation process was characterized by Fourier transform infrared spectroscopy, which the α-helical and β-turned content decreasing by 12.67 % and 5.07 %, respectively, and the content of ordered β-folded structures increasing with heating time, finally increasing to 53.61 % at 24 h. The fluorescence intensity of the endogenous fluorescence spectra decreased and the maximum emission wavelength was red-shifted, suggesting that the fibrillation unfolded the protein structure, hydrolyzed and self-assembled into amyloid fibrils aggregates obscuring the aromatic amino acid residues. The emulsification activity, emulsion stability and viscosity of SPF improved with the increase in protein fibrillation.

Development of composite electrospun films utilizing soy protein amyloid fibrils and pullulan for food packaging applications

Electrospun films (ESF) are gaining attention for active delivery due to their biocompatibility and biodegradability. This study investigated the impact of adding soy protein amyloid fibrils (SAFs) to ESF. Functional ESF based on SAFs/pullulan were successfully fabricated, with SAFs clearly observed entangled in the electrospun fibers using fluorescence microscopy. The addition of SAFs improved the mechanical strength of the ESF threefold and increased its surface hydrophobicity from 24.8° to 49.9°. Moreover, the ESF demonstrated antibacterial properties against Escherichia coli and Staphylococcus aureus. In simulated oral disintegration tests, almost 100% of epigallocatechin gallate (EGCG) dissolved within 4 min from the ESF. In summary, the incorporation of SAFs into ESF improved their mechanical strength, hydrophobicity, and enabled them to exhibit antibacterial properties, making them promising candidates for active delivery applications in food systems. Additionally, the ESF showed efficient release of EGCG, indicating their potential for controlled release of bioactive compounds.

Construction of protein-, polysaccharide- and polyphenol-based conjugates as delivery systems

Natural polymers, such as polysaccharides and proteins, have been used to prepare several delivery systems owing to their abundance, bioactivity, and biodegradability. They are usually modified or combined with small molecules to form the delivery systems needed to meet different needs in food systems. This paper reviews the interactions of proteins, polysaccharides, and polyphenols in the bulk phase and discusses the design strategies, coupling techniques, and their applications as conjugates in emulsion delivery systems, including traditional, Pickering, multilayer, and high internal-phase emulsions. Furthermore, it explores the prospects of the application of conjugates in food preservation, food development, and nanocarrier development. Currently, there are seven methods for composite delivery systems including the Maillard reaction, carbodiimide cross-linking, alkali treatment, enzymatic cross-linking, free radical induction, genipin cross-linking, and Schiff base chemical cross-linking to prepare binary and ternary conjugates of proteins, polysaccharides, and polyphenols. To design an effective target complex and its delivery system, it is helpful to understand the physicochemical properties of these biomolecules and their interactions in the bulk phase. This review summarizes the knowledge on the interaction of biological complexes in the bulk phase, preparation methods, and the preparation of stable emulsion delivery system.

Improvement of kefir fermentation on rheological and microstructural properties of soy protein isolate gels

Soy protein isolate (SPI) has become a promising plant-based material as an animal protein products alternative. However, its application was limited due to the weak gelling properties. To investigate the effect of kefir fermentation on SPI gels properties, SPI-polysaccharide gels was produced by unfermented and kefir-fermented SPI using different concentration of KGM, chitosan, and calcium chloride in this study. Characterization of fermented SPI gels showed that fermentation by kefir grains can be applied to improve the textural strength, mechanical structure, and thermal characteristics of SPI gels. Compared to unfermented SPI gels, the water-holding capacity was remarkably enhanced to 63.11% and 65.71% in fermented SPI-chitosan gels. Moreover, the hardness of fermented SPI-KGM gels were significantly increased to 13.43 g and 27.11 g. And the cohesiveness and resilience of fermented-KGM gels were also improved than unfermented samples. Results of rheological characterization and thermogravimetric analysis revealed the strengthened mechanical features and higher thermal stability of fermented SPI gels. Additionally, the main role of hydrophobic interactions and secondary structure variations of SPI gels were demonstrated by intermolecular force measurements, Fourier-transform infrared spectroscopy, and X-ray diffraction. Moreover, the network structure was observed more compact and homogeneous performed by microstructural images in fermented SPI gels. Therefore, this research provided a novel approach combining multi-species fermentation with protein gelation to prepare SPI gel materials with improved nutrition and structural properties.

Biodegradable Pea Protein Fibril Hydrogel-Based Quasi-Solid-State Zn-Ion Battery

Zinc-ion batteries show great potential as the next-generation power source due to their nontoxic, low-cost, and safe properties. However, issues with zinc anodes, such as dendrite growth and parasitic hydrogen evolution reactions (HERs), must be addressed to commercialize them. Solutions, such as quasi-solid-state electrolytes made from synthetic polymer hydrogels, have been proposed to improve battery flexibility and energy density. However, most polymers used are nonbiodegradable, posing a challenge to sustainability. In this study, hydrogels made from biodegradable poly(vinyl alcohol) and protein nanofibrils from pea protein, a renewable plant-based source, are used as an electrolyte in aqueous zinc-ion batteries. Results show that the flexible and biodegradable hydrogel can enhance the zinc anode stability and effectively restrict HER. This phenomenon is because of the hydrogen-bond network between nanofibril functional groups and water molecules. In addition, the interaction between functional groups on nanofibrils and Zn2+ constructs ion channels for the even migration of Zn2+, avoiding dendrite growth. The Zn||Zn symmetric cell using the hydrogel electrolyte exhibits a long lifespan of over 3000 h and improved capacity retention in the Zn||AC-I2 hybrid ion batteries by suppressing cathode material dissolution. This study suggests the potential of biodegradable hydrogels as a sustainable and effective solution for biodegradable soft powering sources.

Concentration-Regulated Fibrillation of Soy Protein: Structure and In Vitro Digestion

The impact of protein types, heating temperatures, and times on protein fibrillation has been widely studied. However, there is little understanding of the influence of protein concentration (PC) on the protein fibril assembly. In this work, the structure and in vitro digestibility of soy protein amyloid fibrils (SAFs) were investigated at pH 2.0 and different PCs. Significant increases in fibril conversion rate and parallel β-sheets proportion were observed in SAFs upon increasing the PC from 2 to 8% (w/v). The AFM images showed that curly fibrils were prone to form at 2-6% PCs, while rigid, straight fibrils developed at higher PCs (≥8%). As evidenced in XRD results, increasing PC led to a more stable structure of SAFs with enhanced thermal stability and lower digestibility. Moreover, positive correlations among PC, β-sheet content, persistence length, enthalpy, and total hydrolysis were established. These findings would provide valuable insights into concentration-regulated protein fibrillation.

Soy Protein Amyloid Fibril Scaffold for Cultivated Meat Application

It is important to have sustainable and edible scaffolds to produce cultivated meat. In this research, three-dimensional (3D) porous scaffolds were developed by soy protein amyloid fibrils for cultivated meat applications. Food-safe biological and physical cross-linking methods using microbial transglutaminase and temperature-controlled water vapor annealing technique were employed to crosslink soy protein amyloid fibrils, resulting in the production of 3D scaffolds. The generated 3D scaffolds had pores with sizes ranging from 50 to 250 μm, porosities of 72-83%, and compressive moduli of 3.8-4.2 kPa, depending on the type of soy protein used in the process (β-conglycinin (7S), glycinin (11S) and soy protein isolate (SPI)). When present with pepsin, these scaffolds can degrade within an hour but remain stable in phosphate-buffered saline for at least 30 days. The soy protein amyloid fibril scaffolds enabled C2C12 mouse skeletal myoblasts proliferate and differentiate without adding cell adhesive proteins or other coatings. The results demonstrate the potential of abundant and inexpensive soy protein amyloid fibrils to be utilized as scaffold materials for cultivated meat in the food industry.

Producing mixed-soy protein adsorption layers on alginate microgels to controlled-release β-carotene

In this study, the effects of soy protein isolate (SPI) on the morphology, encapsulation efficiency, storage stability, swelling behavior, and in vitro digestion behavior of calcium alginate (CA) microgels were investigated. CA and calcium alginate-SPI (CAS) microgels with encapsulated β-carotene were prepared by extruding a mixture of alginate and SPI using a co-extrusion technique, followed by cross-linking with Ca²⁺. All microgels exhibited homogeneous sizes and spherical shapes, and CAS microgels showed high levels of protein loading efficiency. The encapsulation efficiency and storage stability of β-carotene within CAS microgels were higher than those within CA microgels. The introduction of SPI into CAS microgels resulted in a higher degree of gel size shrinkage in gastric fluid and a lower degree of swelling in intestinal fluid compared to CA microgels. In vitro digestion was conducted to investigate the effects of the addition of SPI on the release behavior of CA and CAS microgels. Results obtained showed that CAS microgels were more resistant to simulated gastric fluid than CA microgels. Cryo-scanning electron microscopy (cryo-SEM) and confocal laser scanning microscopy (CLSM) observations indicated that the release behavior was dependent on the porosity of the CA and CAS microgels, and the porosity was influenced by the concentration of SPI. This study showed that the introduction of SPI to CA microgels can lead to the development of an effective controlled release delivery system.

Binary Hydrogels: Induction Methods and Recent Application Progress as Food Matrices for Bioactive Compounds Delivery-A Bibliometric Review

Food hydrogels are biopolymeric materials made from food-grade biopolymers with gelling properties (proteins and polysaccharides) and a 3D network capable of incorporating large amounts of water. They have sparked considerable interest because of their potential and broad application range in the biomedical and pharmaceutical sectors. However, hydrogel research in the field of food science is still limited. This knowledge gap provides numerous opportunities for implementing their unique properties, such as high water-holding capacity, moderated texture, compatibility with other substances, cell biocompatibility, biodegradability, and high resemblance to living tissues, for the development of novel, functional food matrices. For that reason, this article includes a bibliometric analysis characterizing research trends in food protein-polysaccharide hydrogels (over the last ten years). Additionally, it characterizes the most recent developments in hydrogel induction methods and the most recent application progress of hydrogels as food matrices as carriers for the targeted delivery of bioactive compounds. Finally, this article provides a future perspective on the need to evaluate the feasibility of using plant-based proteins and polysaccharides to develop food matrices that protect nutrients, including bioactive substances, throughout processing, storage, and digestion until they reach the specific targeted area of the digestive system.

Effect of Thermal Treatment on the Self-Assembly of Wheat Gluten Polypeptide

Self-assembled fibrillation of wheat gluten is a common phenomenon in the daily production and processing of wheat flour products. The driving forces for its formation and the factors that influence the morphology of fibrils have not been thoroughly investigated. In this study, the effect of three bonding changes (breaking hydrogen bonds, strengthening hydrophobic interactions, and SH-SS exchange reactions) on gluten polypeptide (GP) fibrillation was simulated by adjusting the heating temperature (room temperature (RT), 45 °C, 65 °C, and 95 °C). The results showed that the breakage of hydrogen bonds could induce conformational transitions in GPs and help to excite fibrillation in GPs. Strengthened hydrophobic interactions significantly contributed to the fibrillation of GPs. Covalent crosslinks generated by SH-SS exchange reactions might also promote the fibrillation of GPs. GPs with different degrees of hydrolysis (4.0%, 6.0%, and 10.0%, represented by DH 4, DH 6, and DH 10, respectively) presented different extents of fibrillation, with DH 10 GPs having a higher propensity to fibrillation than DH 4 and DH 6 GPs. The results of Fourier's transform infrared spectroscopy indicated that hydrophobic interactions drive the transition from a random coil and α-helix to a β-sheet. In addition, hydrophobic interactions also drive the intermolecular polymerization of GPs, resulting in larger molecular weight aggregates. The morphology presented by transmission electron microscopy showed that the greater the DH, the stronger the tendency for the worm-like aggregation of GPs.

Effects of ultrasound pretreatment on functional property, antioxidant activity, and digestibility of soy protein isolate nanofibrils

Nanofibrils, an effective method to modulate the functional properties of proteins, can be promoted by ultrasound pretreatment. This study investigated the effect of ultrasound pretreatment on the structure, functional property, antioxidant activity and digestibility of soy protein isolate (SPI) nanofibrils. The results showed that high amplitude ultrasound had a significant effect on structure of SPI nanofibrils. SPI nanofibrils pretreated by 80% amplitude ultrasound showed a blueshift of the amide II band in Fourier transform infrared spectroscopy (FTIR), resulted in more tryptophan residues being buried and increased the crystallinity. Low amplitude ultrasound (20%) pretreatment significantly improved the solubility, emulsifying activity index (EAI) and water absorption capacity (WAC) of SPI nanofibrils, but 80% amplitude ultrasound pretreatment of SPI nanofibrils reduced emulsifying stability index (ESI). High amplitude ultrasound (60% and 80%) pretreatment of SPI nanofibrils improved the foaming capacity and foaming stability and decreased denaturation temperature. DPPH radical scavenging activity of SPI nanofibrils were significantly improved by ultrasound pretreatment. 20% amplitude ultrasound pretreatment improved DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power of SPI nanofibrils. The digestion rate of 80% amplitude ultrasound-pretreated nanofibrils were consistently higher, and SPI nanofibrils pretreated by ultrasound were more fragmented and shorter after simulating gastrointestinal digestion. This study would expand the application of food-grade protein nanofibrils in the food industry.

YAFAF-Based Hydrogel: Characterization, Mechanism, and Factors Influencing Micro-organization

The YAFAF-based hydrogel was a three-dimensional network cross-linked by grooved fiber bundles. The fiber bundles were formed by entanglement of fibrils with a diameter of 2 nm, and the surface of the fibrils also presented grooves. Spectroscopic analysis revealed that the main secondary structures were β-sheets and β-turns, which led to the grooved feature of fibrils. In comparison of the nuclear magnetic resonance spectra of peptide solutions at 313 and 277 K, the nuclear Overhauser effects can be clearly observed, indicating that hydrogen-bondings and π-π stacking interactions play important roles in self-assembly. The micro-organization of the self-assemblies was affected by the ratio of solvents (x_A) remarkably. Unexpectedly, x_A of 0.05 produced hollow spherical aggregates. The result of these investigations on the mechanism and organization of the YAFAF-based hydrogel can contribute to the development of strategies using hydrogels in the food industry.

Hydrogels: Properties and Applications in Biomedicine

Hydrogels are crosslinked polymer chains with three-dimensional (3D) network structures, which can absorb relatively large amounts of fluid. Because of the high water content, soft structure, and porosity of hydrogels, they closely resemble living tissues. Research in recent years shows that hydrogels have been applied in various fields, such as agriculture, biomaterials, the food industry, drug delivery, tissue engineering, and regenerative medicine. Along with the underlying technology improvements of hydrogel development, hydrogels can be expected to be applied in more fields. Although not all hydrogels have good biodegradability and biocompatibility, such as synthetic hydrogels (polyvinyl alcohol, polyacrylamide, polyethylene glycol hydrogels, etc.), their biodegradability and biocompatibility can be adjusted by modification of their functional group or incorporation of natural polymers. Hence, scientists are still interested in the biomedical applications of hydrogels due to their creative adjustability for different uses. In this review, we first introduce the basic information of hydrogels, such as structure, classification, and synthesis. Then, we further describe the recent applications of hydrogels in 3D cell cultures, drug delivery, wound dressing, and tissue engineering.