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Cellulose nanocrystals are charged rod‐like nanoparticles that can spontaneously organize into cholesteric mesophases upon evaporation to produce photonic films with circular polarization. In this study, it is demonstrated that through the modulation of gelation and kinetics of phase separation via the addition of a strong gelating agent, xanthan gum, the cellulose nanocrystals produce flexible photonic films with improved optical purity in terms of circular reflection. The work reveals the self‐assembly behavior as a function of xanthan gum through the volume depletion mechanism, quenching of the tactoids at the early stages of the self‐assembly, and evaporation into cholesteric films. In dried films, this leads to significant reduction in the domain size and the absence of domain folding which is usually caused by the merger of large tactoids. Despite the reduction in metallic iridescence caused by the entrapment of cellulose nanocrystal tactoids, the films exhibit improved macroscopic color uniformity across 30–60° observation angles, which implies a combined effect of surface texturing and scattering of visible light induced by incorporating xanthan gum within the co‐assembled structure. Overall the work provides new insights into the gelation mechanism in hybrid cellulose nanocrystal systems and presents an efficient approach to control the self‐assembly and macroscopic color appearance. [ABSTRACT FROM AUTHOR]

The industrial application of pea protein is limited due to its poor gelation properties. This study aimed to evaluate the effects of psyllium husk powder (PHP) on improving the rheological, textural, and structural properties of heat-induced pea protein isolate (PPI) gel. Scanning electron microscopy (SEM), intermolecular forces analysis, the quantification of the surface hydrophobicity and free amino groups, and Fourier transform infrared spectroscopy (FTIR) were conducted to reveal the inner structures of PPI-PHP composite gels, conformational changes, and molecular interactions during gelation, thereby clarifying the underlying mechanism. The results showed that moderate levels of PHP (0.5–2.0%) improved the textural properties, water holding capacity (WHC), whiteness, and viscoelasticity of PPI gel in a dose-dependent manner, with the WHC (92.60 ± 1.01%) and hardness (1.19 ± 0.02 N) peaking at 2.0%. PHP significantly increased surface hydrophobicity and enhanced hydrophobic interactions, hydrogen bonding, and electrostatic interactions in PPI-PHP composite gels. Moreover, the electrostatic repulsion between anionic PHP and negatively charged PPI in a neutral environment prevented the rapid and random aggregation of proteins, thereby promoting the formation of a well-organized gel network with more β-sheet structures. However, the self-aggregation of excessive PHP (3.0%) weakened molecular interactions and disrupted the continuity of protein networks, slightly reducing the gel strength. Overall, PHP emerged as an effective natural gel enhancer for the production of pea protein gel products. This study provides technical support for the development of innovative plant protein-based foods with strong gel properties and enriched dietary fiber content. [ABSTRACT FROM AUTHOR]

Over the years, the production of eggs has increased tremendously, with an estimated global egg production of 9.7 billion by 2050. Further processing of shell eggs to egg products has gained growing popularity. Liquid egg yolks, an innovative form of egg replacement, still suffer from short shelf‐life issues, and freezing has been applied to maintain freshness. An undesirable phenomenon called "gelation" was found during the production of frozen egg yolks, which has attracted numerous scholars to study its mechanism and quality control methods. Therefore, we comprehensively reviewed the history of the studies on frozen egg yolks, including the production procedure, the fundamentals of freezing, the gelation mechanism, the factors affecting gelation behaviors, and the techniques to control the gelation behaviors of frozen egg yolks. Reporting the production procedure and freezing fundamentals of frozen egg yolks will give readers a better understanding of the science and technological aspects of frozen egg yolks. Furthermore, a comprehensive summary of the mechanism of egg yolk gel formation induced by freeze–thawing and relevant control techniques will provide insights to researchers and manufacturers in the field of frozen egg processing. [ABSTRACT FROM AUTHOR]

A novel fire-preventing composite gel, mainly made from steel slag (SS) and silica fume (SF), was created for a coal mine’s spontaneous combustion. The gelation mechanism of the steel slag-based composite gel (SSG) was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (SEM). The findings suggest that SSG is generated through the processes of hydration and geopolymerization involving SS and SF. And in the alkaline milieu of a 1.5 M water glass solution, SSG manifests enhanced strength and water retention capacities. Moreover, the fire prevention and extinguishing performance of the SSG was analyzed and verified using low-temperature oxidation, thermogravimetry, and low temperature nitrogen adsorption experiment (LTNA). The SSG has proven highly effective in suppressing spontaneous coal combustion by inhibiting CO production, raising the coal oxidation temperature, and reducing the contact area between oxygen and the coal body.

Gelation, an important quality attribute of meat products, significantly influences the appearance, flavor, and texture of meat products. Enhancing gelation in meat products holds immense importance in improving the production process and the quality. The gel properties of meat products are influenced by the content and structure of protein aggregates and the aggregation rate during processing. Protein additives have the potential to partially replace myofibrillar proteins in gelation and emulsification properties, leading to cost reduction, and therefore have attracted much research interest for the development of new meat products and the optimization of the processing technology. This paper summarizes recent studies on the gelation mechanism of myofibrillar proteins, and reviews the properties and applications of the major protein additives as well as recent progress in using protein additives combined with polysaccharide colloids, enzymes or phosphates to enhance the gelation of meat products. This review may serve as a valuable reference for enhancing the quality of gel-type meat products.

To investigate the effect of the chemical composition of a metal–organic crosslinker on the performances of fracturing fluid in high-temperature conditions, four zirconium (Zr) crosslinkers and one aluminum–zirconium (Al-Zr) crosslinker with a polyacrylamide were used. The crosslinkers possessed the same Zr concentration, but they differed in component amounts and the order of the addition of the crosslinker components, leading to different chemical compositions in the crosslinkers. The fracturing fluids prepared by different tested crosslinkers were compared in terms of properties of rheological behavior, sand-carrying ability, microstructure, and gel breaking characteristics. The results showed that the fracturing fluids prepared by zirconium lactic acid, ethanediamine, and sorbitol crosslinkers offered the slowest viscosity development and highest final viscosity compared to the zirconium lactic acid crosslinker and the zirconium lactic acid and ethanediamine crosslinker. The zirconium sorbitol, lactic acid, and ethanediamine crosslinker exhibited a faster crosslinking rate and a higher final viscosity than the zirconium lactic acid, ethanediamine, and sorbitol crosslinker; the crosslinker showed crosslinking density and crosslinking reactivity, resulting in more crosslinking sites and a higher strength in the fracturing fluid. The Al-Zr-based crosslinker possessed better properties in temperature and shear resistance, viscoelasticity, shear recovery, and sand-carrying ability than the Zr-based crosslinker due to the synergistic crosslinking effect of aluminum and zirconium ions. The tertiary release gelation mechanism of the Al-Zr-based fracturing fluid achieved a temperature resistance performance in the form of continuous crosslinking, avoiding the excessive crosslinking dehydration and reducing viscosity loss caused by early shear damage. These results indicated that the chemical compositions of metal–organic crosslinkers were important factors in determining the properties of fracturing fluids. Therefore, the appropriate type of crosslinker could save costs without adding the additional components required for high-temperature reservoirs. [ABSTRACT FROM AUTHOR]

Heating is a vital step in the gelation of surimi. Conventional water bath heating (WB) has the advantages of easy operation and low equipment requirements. However, the slow heat penetration during WB may lead to poor gel formation or gels prone to deterioration, especially with one-step heating. The two-step WB is time-consuming, and a large amount of water used tends to cause environmental problems. This review focuses on key factors affecting the quality of surimi gels in various heating technologies, such as surimi protein structure, chemical forces, or the activity of endogenous enzymes. In addition, the relationships between these factors and the gel performance of surimi under various heating modes are discussed by analyzing the heating temperature and heating rate. Compared with WB, the gel performance can be improved by controlling the heating conditions of microwave heating and ohmic heating, which are mainly achieved by changing the molecular structure of myofibrillar proteins or the activity of endogenous enzymes in surimi. Nevertheless, the novel thermal technologies still face several limitations and further research is needed to realize large-scale industrial production. This review provides ideas and directions for developing heat-induced surimi products with excellent gel properties. [ABSTRACT FROM AUTHOR]

The objective of this study is to enhance the comprehension of the mechanism of enzymatic gelation in milk by investigating statistically significant changes in milk viscosity and carrying out corresponding electron microscopic studies of the process of structure formation at the enzymatic stage of coagulation using various enzyme preparations. Employing a non-destructive method (Hot-Wire) to monitor viscosity, we were able to confirm a decrease in viscosity during the middle of this stage and identify a previously undescribed peak in viscosity change at the end of the enzymatic stage. By conducting parallel studies utilizing transmission electron microscopy and various methods of specimen preparation, it was possible to discover that a hierarchical transformation process in the protein component of milk started at the end of the enzymatic stage of gelation in milk. This process is triggered by a cooperative conformational transition in casein micelle clusters, which leads to a series of increasingly energy-intensive reactions resulting in the transformation of loosely bound micelle clusters into denser aggregates. The final structure of the milk gel primarily consists of the previously formed individual micelle aggregates. It was noted that no changes in the microstructure of the milk gel were observed during the enzymatic stage of gelation when milk-clotting enzymes (MCEs) of animal, plant, and microbial (GMO) origins were used. Furthermore, investigations into the molecular weight distribution of soluble protein substances in samples generated with different types of MCEs revealed that the enzyme derived from the fungi of Rhizomucor miehei had a greater proteolytic effect on milk proteins compared to other variants of MCEs. [ABSTRACT FROM AUTHOR]

In situ gel systems have emerged as promising drug delivery platforms due to their numerous benefits, including increased patient compliance and decreased administration frequency. The potential of in situ gel extends beyond its formulation benefits, with the ability to transform medical treatment by enhancing drug delivery, offering personalized therapies, and introducing innovative approaches. Ongoing research and the efforts of pharmaceutical companies are dedicated to exploring the vast opportunities presented by in situ gel, pushing the limits of innovation in the field of drug delivery. The selection of suitable polymers is critical for the development of in situ gel formulations. Additionally, consideration of drug‐polymer compatibility ensures the stability and efficacy of the drug within the gel matrix. Formulation considerations play a pivotal role in the development of effective in situ gel systems. They have shown great potential in drug delivery systems, tissue engineering, and regenerative medicine. The ability to prolong gastric retention time, targeted delivery, and localized drug release are among the advantages offered by in situ gels. Although in situ gel technology has shown significant advancements, challenges remain, including stability and shelf‐life issues, biocompatibility and safety concerns, and the need for further research and development. Future directions focus on overcoming these challenges and exploring new applications and advancements in the field. In conclusion, in situ gel systems provide a versatile and promising drug delivery and tissue engineering platform. However, further research and development are essential to address the challenges and fully harness the potential of this innovative technology. [ABSTRACT FROM AUTHOR]

The industrial application of pea protein is limited due to its poor gelation properties. This study aimed to evaluate the effects of psyllium husk powder (PHP) on improving the rheological, textural, and structural properties of heat-induced pea protein isolate (PPI) gel. Scanning electron microscopy (SEM), intermolecular forces analysis, the quantification of the surface hydrophobicity and free amino groups, and Fourier transform infrared spectroscopy (FTIR) were conducted to reveal the inner structures of PPI-PHP composite gels, conformational changes, and molecular interactions during gelation, thereby clarifying the underlying mechanism. The results showed that moderate levels of PHP (0.5–2.0%) improved the textural properties, water holding capacity (WHC), whiteness, and viscoelasticity of PPI gel in a dose-dependent manner, with the WHC (92.60 ± 1.01%) and hardness (1.19 ± 0.02 N) peaking at 2.0%. PHP significantly increased surface hydrophobicity and enhanced hydrophobic interactions, hydrogen bonding, and electrostatic interactions in PPI-PHP composite gels. Moreover, the electrostatic repulsion between anionic PHP and negatively charged PPI in a neutral environment prevented the rapid and random aggregation of proteins, thereby promoting the formation of a well-organized gel network with more β-sheet structures. However, the self-aggregation of excessive PHP (3.0%) weakened molecular interactions and disrupted the continuity of protein networks, slightly reducing the gel strength. Overall, PHP emerged as an effective natural gel enhancer for the production of pea protein gel products. This study provides technical support for the development of innovative plant protein-based foods with strong gel properties and enriched dietary fiber content.

To investigate the effect of the chemical composition of a metal–organic crosslinker on the performances of fracturing fluid in high-temperature conditions, four zirconium (Zr) crosslinkers and one aluminum–zirconium (Al-Zr) crosslinker with a polyacrylamide were used. The crosslinkers possessed the same Zr concentration, but they differed in component amounts and the order of the addition of the crosslinker components, leading to different chemical compositions in the crosslinkers. The fracturing fluids prepared by different tested crosslinkers were compared in terms of properties of rheological behavior, sand-carrying ability, microstructure, and gel breaking characteristics. The results showed that the fracturing fluids prepared by zirconium lactic acid, ethanediamine, and sorbitol crosslinkers offered the slowest viscosity development and highest final viscosity compared to the zirconium lactic acid crosslinker and the zirconium lactic acid and ethanediamine crosslinker. The zirconium sorbitol, lactic acid, and ethanediamine crosslinker exhibited a faster crosslinking rate and a higher final viscosity than the zirconium lactic acid, ethanediamine, and sorbitol crosslinker; the crosslinker showed crosslinking density and crosslinking reactivity, resulting in more crosslinking sites and a higher strength in the fracturing fluid. The Al-Zr-based crosslinker possessed better properties in temperature and shear resistance, viscoelasticity, shear recovery, and sand-carrying ability than the Zr-based crosslinker due to the synergistic crosslinking effect of aluminum and zirconium ions. The tertiary release gelation mechanism of the Al-Zr-based fracturing fluid achieved a temperature resistance performance in the form of continuous crosslinking, avoiding the excessive crosslinking dehydration and reducing viscosity loss caused by early shear damage. These results indicated that the chemical compositions of metal–organic crosslinkers were important factors in determining the properties of fracturing fluids. Therefore, the appropriate type of crosslinker could save costs without adding the additional components required for high-temperature reservoirs.

Various polymers are the most widely used product to provide rheology for water-based fracturing fluid, however, they have weaknesses in terms of temperature resistance and salt resistance. The change from organic-based to inorganic thickeners may be a meaningful attempt. Inorganic silica gel is a potentially alternative viscosifier with high temperature resistance, excellent proppant carrying capacity, and can even be used to prepare fracturing fluids with high salinity of produced water. In this paper, the silica gel viscosifier was firstly prepared using sol–gel method. Then, the gelation time under different influencing factors and rheological properties of the silica gel viscosifier were studied in detail. Subsequently, the silica gel-based fracturing fluid was prepared by adding the desired amount of drag reducer to the silica sol solution, and the properties of novel fracturing fluid were systematically evaluated with regard to the temperature and shearing resistance, drag reduction, and static proppant suspension. The potential mechanism of gelation process by syneresis of silica gel was revealed at last. Results showed that the microstructure of silica gel is synthetic, amorphous and consists of a three-dimensional network of SiO2 particles. The effect of SiO2 concentration on the gelation time is more pronounced than other factors such as temperature and pH level. In addition, the silica gel viscosifier exhibits strong salt resistance, whether monovalent ions (Na+, K+) or divalent ions (Ca2+, Mg2+), and the gelation time decreased significantly with the increase of salt concentration. The shear viscosity of the silica gel viscosifier increased with an increase of SiO2 concentration, showing shear thinning behavior as well. Meanwhile, the silica gel-based fracturing fluid prepared by adding drag reducer into silica sol solution also presented excellent thermal stability and shear resistance, drag reduction and proppant suspension performances. The retained viscosity can be maintained above 50 mPa·s after shearing at 180 °C for 60 mins; the drag reduction rate shows a declining trend at high displacement due to the gelation process; the settling rate of 40/70 mesh sand proppant with 35 % sand ratio is less than 30 % after standing at 90 °C for 4 h. In addition, the gelation process is essentially the formation of Si-O-Si linkage by dehydration between SiO2 particles, which is gradually extended at both ends and sides of the chain, and eventually forms a rigid, highly porous, entangled network. Findings found in this study provide a research basis for the popularization and application of silica gel-based fracturing fluid.

To expand the applicability of gel fracturing fluids in ultra-high-temperature reservoirs, a temperature-resistant polymer was synthesized using the solution polymerization method. Subsequently, an ultra-high-temperature-resistant polymer gel was formulated by incorporating an organic zirconium crosslinking agent. A comprehensive investigation was carried out to systematically study and evaluate the steady shear property, dynamic viscoelasticity, and temperature and shear resistance performance, as well as the core damage characteristics of the polymer gel. The obtained results demonstrate that the viscosity remained at 147 mPa·s at a temperature of 200 °C with a shear rate of 170 s−1. Compared with the significant 30.9% average core damage rate observed in the guanidine gum fracturing fluid, the core damage attributed to the polymer gel was substantially mitigated, measuring only 16.6%. Finally, the gelation mechanism of the polymer gel was scrutinized in conjunction with microscopic morphology analysis. We expect that this study will not only contribute to the effective development of deep and ultradeep oil and gas reservoirs but also furnish a theoretical foundation for practical field applications. [ABSTRACT FROM AUTHOR]

So far, it has been difficult to directly compare diverse characteristic gelation mechanisms over different length and time scales. This paper presents a universal water structure analysis of several gels with different structures and gelation mechanisms including polymer gels, supramolecular gels composed of surfactant micelles, and cement gels. The spatial distribution of water molecules was analyzed at molecular level from a diagram of the relaxation times and their distribution parameters (τ–β diagrams) with our database of the 10 GHz process for a variety of aqueous systems. Polymer gels with volume phase transition showed a small decrease in the fractal dimension of the hydrogen bond network (HBN) with gelation. In supramolecular gels with rod micelle precursor with amphipathic molecules, both the elongation of the micelles and their cross-linking caused a reduction in the fractal dimension. Such a reduction was also found in cement gels. These results suggest that the HBN inevitably breaks at each length scale with relative increase in steric hindrance due to cross-linking, resulting in the fragmentation of collective structures of water molecules. The universal analysis using τ–β diagrams presented here has broad applicability as a method to characterize diverse gel structures and evaluate gelation processes. [ABSTRACT FROM AUTHOR]

This article reviews different studies on the gelation mechanisms and network structural characteristics in polysaccharide gels at the different length scales of observation: macroscopic, microscopic, and molecular. Rheological and micro-DSC (Differential Scanning Calorimetry) measurements represent the macroscopic viewpoints on the gelation of pure kappa-carrageenan (KC), iotacarrageenan (IC) and KC/IC mixtures. Microscopic rheological properties observed using particle tracking experiments have been used to elucidate the formation of heterogeneous networks of KC-rich and IC-rich domains in mixed KC/IC gels, and facilitate observations of their aging process. Nuclear magnetic resonance (NMR) relaxation time measurements provide information on the tumbling motion and local mobility; these molecular-level experiments are presented for agar, agarose, native gellan and deacylated gellan chains. NMR diffusion measurements of gelling and probe polymers give insights into the conformational changes, aggregation and network formation, and aging mechanisms, and are presented for all studied polysaccharides. [ABSTRACT FROM AUTHOR]

Highlights Metal–organic frameworks (MOFs) are used to directly initiate the gelation of graphene oxide (GO), producing MOF/rGO aerogels. The ultralight magnetic and dielectric aerogels show remarkable microwave absorption performance with ultralow filling contents. Abstract The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal–organic frameworks (MOFs) and graphene oxide (GO) building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications. Herein, we report a facile route for synthesizing MOF/reduced GO (rGO) aerogels based on the gelation of GO, which is directly initiated using MOF crystals. Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal–oxygen covalent or electrostatic interactions. The MOF/rGO-derived magnetic and dielectric aerogels Fe3O4@C/rGO and Ni-doped Fe3O4@C/rGO show notable microwave absorption (MA) performance, simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5 (− 58.1 dB and 6.48 GHz) and 2.8 mm (− 46.2 dB and 7.92 GHz) with ultralow filling contents of 0.7 and 0.6 wt%, respectively. The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation, which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering. This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA.

Surimi gels are highly valued by consumers owing to their rich nutrients, distinctive flavor, and easily adjustable gel texture. Typically, 2%–3% salt is added to achieve optimal gel characteristics during surimi processing. However, excessive salt intake poses substantial health risks. Consequently, the urgent need to reduce the salt content in surimi gels is a new trend in the current food industry development. This study provides a comprehensive overview of the gelatinization mechanism of myosin. In addition, it explores the principles of salt-reduction techniques for modulating myosin gelation behavior, highlighting their limitations and their prepared quality characteristics of reduced-salt surimi gels. Moreover, the future prospects of reduced-salt surimi gels are discussed in relation to their functional properties. The gel formation mechanism of surimi has two critical steps: initial myosin solubilization and heat treatment. However, low-salt conditions restrict myosin solubilization, hindering the formation of high-quality gels. Recently, emerging processing technologies have gained considerable attention for their ability to modify protein interactions, becoming a focal point in salt-reduction research. In addition to their food applications, reduced-salt surimi gels have considerable potential for use in the medical and healthcare sectors. Utilizing three-dimensional (3D) printing technology, special functional reduced-salt surimi gel products can be designed, allowing personalized and precise nutrition delivery. The ultimate goal was to achieve the widespread production of high value–added surimi gel products. • The gelation mechanism of myosin and its influencing factors are listed in detail. • The assembly behavior of myosin is related to salt concentration and heating temperature. • Salt-reduction mechanisms of surimi gels under different processing methods are summarized. • Enhancing reduced-salt surimi for health products faces ongoing challenges. [ABSTRACT FROM AUTHOR]

Chickpea protein isolate (CPI) emulsion gels suffered from poor elasticity and loose structure, which greatly limited their application and development. This work aimed to investigate the effect of cellulose nanofibrils (CNFs) on the intermolecular interactions, protein structure, gel properties, and microstructure of CPI emulsion gels. Results showed that CNFs enhanced the hydrophobic interactions, electrostatic interactions, and hydrogen bonding of the CPI emulsion gels, and contributed to the transition of the secondary structure of CPI from α-helix to β-sheet structure. CPI-CNFs emulsion gels exhibit better textural properties, rheological properties and water holding capacity compared to CPI emulsion gels. Gel strength increased from 40.67 g to 56.26 g and hardness increased from 42.95 g to 60.67 g. Furthermore, scanning electron microscopy showed that the CPI emulsion gel structures were transformed from rough and porous to uniform and dense with the addition of CNFs. This study indicated that CNFs will help improve the properties of CPI emulsion gels with wide applications in the food field. [Display omitted] • Cellulose nanofibrils (CNFs) improved the gel properties of chickpea protein isolate (CPI). • Hydrogen bonding, disulfide bonds, and hydrophobic interactions were the main driving forces. • CNFs addition further improved the microstructure of CPI emulsion gels. • CNFs promoted the transition from α-helix to β-sheet in CPI emulsion gels. [ABSTRACT FROM AUTHOR]

A novel fire-preventing composite gel, mainly made from steel slag (SS) and silica fume (SF), was created for a coal mine's spontaneous combustion. The gelation mechanism of the steel slag-based composite gel (SSG) was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (SEM). The findings suggest that SSG is generated through the processes of hydration and geopolymerization involving SS and SF. And in the alkaline milieu of a 1.5 M water glass solution, SSG manifests enhanced strength and water retention capacities. Moreover, the fire prevention and extinguishing performance of the SSG was analyzed and verified using low-temperature oxidation, thermogravimetry, and low temperature nitrogen adsorption experiment (LTNA). The SSG has proven highly effective in suppressing spontaneous coal combustion by inhibiting CO production, raising the coal oxidation temperature, and reducing the contact area between oxygen and the coal body. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of oat β-glucan on the formation mechanism, microstructure and physicochemical properties of konjac glucomannan (KGM) composite hydrogel. The dynamic rheology results suggested that the addition of oat β-glucan increased the viscoelastic modulus of the composite hydrogel, which was conducive to the formation of a stronger gel network. Gelling force experiments showed that hydrogen bonds and hydrophobic interactions participated in the formation of the gel network. Textural profile analysis results found that the amount of oat β-glucan was positively correlated with the elasticity, cohesiveness and chewiness of the composite hydrogel. The water-holding capacity of the composite hydrogel was enhanced significantly after the addition of oat β-glucan (p < 0.05), which was 18.3 times that of the KGM gel. The thermal stability of KGM gel was enhanced after the addition of oat β-glucan with the increase in Tmax being approximately 30 °C. Consequently, a composite hydrogel based on KGM and oat β-glucan was a strategy to overcome pure KGM gel shortcomings. [ABSTRACT FROM AUTHOR]

Highlights: Metal–organic frameworks (MOFs) are used to directly initiate the gelation of graphene oxide (GO), producing MOF/rGO aerogels. The ultralight magnetic and dielectric aerogels show remarkable microwave absorption performance with ultralow filling contents. The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal–organic frameworks (MOFs) and graphene oxide (GO) building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications. Herein, we report a facile route for synthesizing MOF/reduced GO (rGO) aerogels based on the gelation of GO, which is directly initiated using MOF crystals. Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal–oxygen covalent or electrostatic interactions. The MOF/rGO-derived magnetic and dielectric aerogels Fe3O4@C/rGO and Ni-doped Fe3O4@C/rGO show notable microwave absorption (MA) performance, simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5 (− 58.1 dB and 6.48 GHz) and 2.8 mm (− 46.2 dB and 7.92 GHz) with ultralow filling contents of 0.7 and 0.6 wt%, respectively. The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation, which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering. This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA. [ABSTRACT FROM AUTHOR]

In this study, the influences of various concentrations of β-cyclodextrin (β-CD) on the gelation properties of curdlan thermo-irreversible gels were evaluated. The results revealed that water-holding capacity and freeze-thaw stability of the curdlan/β-CD complex gels initially increased but then decreased with increasing β-CD concentration, with the curdlan gel containing 1 % (w/v) β-CD demonstrating the best performance. Moreover, textural characteristics including hardness, gumminess, cohesiveness, and chewiness exhibited similar trends, but springiness showed minor effect. Compared with the pure curdlan gel, the curdlan/β-CD mixed gels exhibited better elastic behavior and greater thermal stability but lower crystallinity. Additionally, scanning electron microscopy (SEM) images of the curdlan/β-CD composite gels revealed fine network structures with relatively continuous pores. The intermolecular hydrogen bonds between curdlan and β-CD were responsible for the enhanced gel properties. Thus, these data suggest that the inclusion of β-CD ameliorates the texture and stability of the curdlan gel by forming hydrogen bonds., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

To expand the applicability of gel fracturing fluids in ultra-high-temperature reservoirs, a temperature-resistant polymer was synthesized using the solution polymerization method. Subsequently, an ultra-high-temperature-resistant polymer gel was formulated by incorporating an organic zirconium crosslinking agent. A comprehensive investigation was carried out to systematically study and evaluate the steady shear property, dynamic viscoelasticity, and temperature and shear resistance performance, as well as the core damage characteristics of the polymer gel. The obtained results demonstrate that the viscosity remained at 147 mPa·s at a temperature of 200 °C with a shear rate of 170 s−1. Compared with the significant 30.9% average core damage rate observed in the guanidine gum fracturing fluid, the core damage attributed to the polymer gel was substantially mitigated, measuring only 16.6%. Finally, the gelation mechanism of the polymer gel was scrutinized in conjunction with microscopic morphology analysis. We expect that this study will not only contribute to the effective development of deep and ultradeep oil and gas reservoirs but also furnish a theoretical foundation for practical field applications.

Pectins are acidic hetero-polysaccharides present in plant primary cell walls. With strong and interesting gelation capacity, some plant-sourced pectins including Nicandra physalodes (Linn.) Gaertn. pectin (NPGP) , Premna microphylla turcz pectin (PMTP) , and creeping fig pectin (CFP), have been traditionally used in making gel foods in China. However, little is known about their gelation behaviors and the mechanisms involved. In this review, the extraction, structures , gelation behaviors and the underlying mechanisms of NPGP, PMTP and CFP are introduced. Moreover, the structure-property relation of major pectin types (i.e. commercial citrus and apple pectins) is also summarized for providing a deep understanding on pectin gelation. Both the intrinsic pectin structures and extrinsic environmental factors significantly affect the gelation of pectins. The interplay between these factors is also important, which sometimes can impart pectins with unexpected gelation behaviors. For NPGP , PMTP and CFP, all of them possess a relatively high galacturonic acid (GalA) content and a very low DM value, which allow them to behave like the typical "polyelectrolytes" and make them highly sensitive to the presence of cations. Monovalent cations (e.g. Na+ and/or H+) are able to induce the gelation of these pectins at appropriate conditions. Besides, NPGP , PMTP, and CFP can also form Ca2+-induced gels at ambient temperature with a moderate gelling rate, which is rarely reported for citrus and apple pectins. The underlying mechanism is still unclear at this moment. Therefore, the structure-property relation on pectin gelation needs to be further explored. • Some plant-sourced low methoxyl pectins can gel in the absence of calcium ions. • Synergism can be adopted to enhance the rheological and gelling ability of pectins. • Spontaneous gelation was found to occur for creeping fig pectins. • These plant-sourced pectins can form Ca2+-induced gels at room temperature. • The understanding on the structure-property relation of pectins is still insufficient. [ABSTRACT FROM AUTHOR]

Protein gelation can provide texture in plant-based foods and can be influenced by many factors, including protein extraction method and salt addition. However, the protein gelation mechanism is still not well understood for plant proteins, especially for isolates obtained using commercial protein extraction processes. Therefore, the structural changes that legume sources such as yellow pea, faba bean, and soybeans undergo during the gelation process to understand the differences in their gelation mechanisms was investigated herein by using small-angle neutron scattering. Among these protein sources, the commercial extraction method was found to play a major part in the gelation pathway. Intensive protein extraction methods involving isoelectric precipitation led to lower protein solubility (∼1–38% w/w), larger insoluble protein particle sizes (60–100 μm), and a gelation pathway that is dependent on the changes of the insoluble protein particles. In contrast, extraction using ultrafiltration instead of precipitation resulted in higher protein solubility (∼18–88% w/w) and smaller insoluble protein particle sizes (40–70 μm), and the structural changes observed during gelation involved the structural changes of both soluble proteins and insoluble proteins. SEM imaging also showed different gel networks, with fractal networks formed by insoluble proteins (for sources with low solubility) or more homogenous networks formed by the interactions between the soluble proteins (for sources with high solubility). Despite the differences observed in the gelation network and the protein solubility, the gelation strength exhibited by protein sources at low protein solubility were similar to the ones by protein sources at high protein solubility, demonstrating the potential of fractal gel networks in providing texture. [Display omitted] • Protein structural changes are dependent on solvent pH and salt content. • Different gel network structures can exhibit similar gel strengths. • Less soluble protein sources form gel networks with insoluble protein particles. • More soluble protein sources form a homogeneous network around insoluble particles. [ABSTRACT FROM AUTHOR]

Natural polysaccharide sources have attracted widespread attention in the food, medical and beauty industries because of their range of biological activities. To investigate the gel functional properties and underlying mechanisms of the interaction between Dendrobium officinale polysaccharide (DOP) and κ-carrageenan (KC), a comprehensive analysis was conducted using various instruments, such as rheometers, texture analysers, scanning electron microscopes, and Fourier transform infrared spectroscopy. When the ratio of NK/ND (DK) was 1:1, the gel strength, water-holding capacity, swelling capacity, freeze‒thaw stability, and moisturizing properties were improved compared with those of NK and ND. Moreover, the sol‒gel transition temperature decreased after the combined use of NK and ND, indicating better flexibility and moisturizing properties. Additionally, the addition of the hydrogen bond breaker urea significantly decreased the storage modulus (G′) of the gel, whereas the addition of an electrostatic force breaker increased the G′ value, highlighting the crucial roles of hydrogen bonds and electrostatic forces in its gel network formation. Furthermore, the addition of glucuronic acid demonstrated that the carboxyl groups on the DK chains are involved in maintaining the formation of inter- and intra-hydrogen bonds in the DK gel network. Moreover, the molecular docking results revealed hydrogen bonding interactions between NK and ND, which are combined through helical twisting. In summary, DK achieves synergy through physical cross-linking, and its excellent water-holding, moisturizing, and adhesive properties suggest its potential as a wound dressing. [Display omitted] • DOP and KC form gel with improved gel quality by synergistic interaction. • DOP intersperse among fibrous structures of KC to obtain an ordered system. • Synergistic effect is due to hydrogen bonding formation between two polysaccharides. • DOP filled between KC acts as a powerful scaffold to provided support for the gel. [ABSTRACT FROM AUTHOR]

Silk fibroin hydrogel not only has biocompatibility, but also has environmental response ability. It plays an important role in the development of material. The gelation mechanism of silk fibroin hydrogel is very important to textile and medicine fields. The molecular dynamics simulation was used to discuss the structure and non-bond interaction of silk fibroin hydrogel. The results show that the non-bond interactions between silk fibroin molecules and water molecules have certain influence on the formation of silk fibroin hydrogel. According to the hydrogen bond analysis, the hydrogen bonds are mainly formed between random coil peptide fragments at the two ends of silk fibroin molecules and residues 252-254 are the key residues. The electrostatic and polar solvation interactions between silk fibroin molecules plays a major role in cross-linking of the coil segments of two silk fibroin molecules.

So far, it has been difficult to directly compare diverse characteristic gelation mechanisms over different length and time scales. This paper presents a universal water structure analysis of several gels with different structures and gelation mechanisms including polymer gels, supramolecular gels composed of surfactant micelles, and cement gels. The spatial distribution of water molecules was analyzed at molecular level from a diagram of the relaxation times and their distribution parameters (τ–β diagrams) with our database of the 10 GHz process for a variety of aqueous systems. Polymer gels with volume phase transition showed a small decrease in the fractal dimension of the hydrogen bond network (HBN) with gelation. In supramolecular gels with rod micelle precursor with amphipathic molecules, both the elongation of the micelles and their cross-linking caused a reduction in the fractal dimension. Such a reduction was also found in cement gels. These results suggest that the HBN inevitably breaks at each length scale with relative increase in steric hindrance due to cross-linking, resulting in the fragmentation of collective structures of water molecules. The universal analysis using τ–β diagrams presented here has broad applicability as a method to characterize diverse gel structures and evaluate gelation processes.

Mung bean protein isolate (MBPI) has attracted much attention as an emerging plant protein. However, its application was limited by the poor gelling characteristics. Thus, the effect of sanxan (SAN) on the gelling behavior of MBPI under microbial transglutaminase (MTG)-induced condition were explored in this study. The results demonstrated that SAN remarkably enhanced the storage modulus, water-holding capacity and mechanical strength. Furthermore, SAN changed the microstructure of MBPI gels to become more dense and ordered. The results of zeta potential indicated the electrostatic interactions existed between SAN and MBPI. The incorporation of SAN altered the secondary structure and molecular conformation of MBPI, and hydrophobic interactions and hydrogen bonding were necessary to maintain the network structure. Additionally, in vitro digestion simulation results exhibited that SAN remarkably improved the capability of MBPI gels to deliver bioactive substances. These findings provided a practical strategy to use natural SAN to improve legume protein gels. [Display omitted] • SAN could enhance the overall structure of MBPI gels. • SAN interacted with MBPI mainly via hydrophobic interaction and hydrogen bond. • Simultaneous covalent and non-covalent interactions in MBPI-SAN composite gel. • MBPI-SAN composite gel had a more compact and uniform microstructure. • MBPI-SAN composite gel showed effective protection against Cur by in vitro digestion. [ABSTRACT FROM AUTHOR]

The object of research is natural polysaccharides. One of the problems is the high cost and not always environmental friendliness of foreign analogues of these substances. Therefore, the methods of purification of polydisperse systems with the help of dispersed minerals, in particular separated dispersed mineral glauconite, purified and enriched up to 60 % of the initial content, are proposed. The study used aqueous solutions of dextran and pectin, which added glauconite in the amount of 0.3 to 0.9 % by weight of the solution, heated to 60 °C and kept for 10 minutes. Using glauconite in the amount of 0.3 % by weight of the solution gave high quality indicators. Thus, the dependence of the viscosity of polysaccharides dextran and pectin on the concentration of the introduced mineral was studied. The lowest value of viscosity is observed when adding 0.3 % glauconite to the mass of the solution, with increasing concentration, the viscosity increases. The process of interaction of dextran molecules with the surface of glauconite is due to the fact that the proposed method of studying the viscosity has a feature that connects neighboring mineral particles through the dextran bridge and the formation of a stable gel structure. These structures are manifested in the form of partial groups of glauconite. This provides the ability to obtain such an indicator as adsorption. The mechanism of interaction of dextran with glauconite is confirmed by the dependence of the amount of dextran adsorbed on the surface of the mineral. Thus, at low concentrations of glauconite – up to 0.3 % adsorption of dextran on the surface increases, and with increasing concentration of glauconite – greatly decreases. This is crucial for the technological parameters of the mineral when using it in preparation processes, in comparison with similar adsorbents of unnatural origin. This will provide the benefits of glauconite over the use in the food industry and the regulation of the physicochemical properties of industrial polydisperse solutions as inexpensive additives of natural origin (stabilizers, thickeners, etc.) that are harmless to human health. [ABSTRACT FROM AUTHOR]

Konjac glucomannan (KGM) is a functional polysaccharide isolated from the tubers of Amorphophallus konjac C. Koch known for its superior heat-set gel-forming capacity. Although commonly used for decades in food industry, KGM's unique gelling behavior has drawn lots of attention in recent years, and it also presents significant challenges especially when elucidating its gelation mechanism. In this review, recent progress and developments on gelation mechanism of the alkali induced heat-set KGM gel have been summarized on many key topics, including the experimental techniques, differences between gel preparation routes, and most importantly, correlating morphological/structural features and intermolecular interactions during the gelling process. In addition, impacts of internal and external factors on the KGM gelation, especially the mechanically related properties, have been also discussed. The understanding of KGM gelation has been evolving over the last decade. The possible gelation includes the deacetylation induced by alkali addition, the stretch and physically association of chains upon heat-treatment, and the three-dimensional gel network established on the agglomeration of random network. Although insights have been provided into the gelation mechanism of KGM in this review which uncovers the foundational aspects of structure/property relationships in terms of KGM gel. There are still unanswered questions and areas, in particular the alkali and heat-treatment induced intermolecular association mechanism, where further research employing some state-of-the-art in situ characterization techniques as well as computation models is required. [Display omitted] • Gelation mechanism of alkali-induced heat-set KGM gel is updated. • Changes in gel morphology and structure across the time scale are discussed. • Factors including KGM concentration and temperature can strongly affect the gel formation and property. • Impact of swelling on alkali induced heat-set KGM gels is yet to be illustrated. • The underlying mechanism of heat-treatment induced intermolecular association remains unknown. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of oat β-glucan on the formation mechanism, microstructure and physicochemical properties of konjac glucomannan (KGM) composite hydrogel. The dynamic rheology results suggested that the addition of oat β-glucan increased the viscoelastic modulus of the composite hydrogel, which was conducive to the formation of a stronger gel network. Gelling force experiments showed that hydrogen bonds and hydrophobic interactions participated in the formation of the gel network. Textural profile analysis results found that the amount of oat β-glucan was positively correlated with the elasticity, cohesiveness and chewiness of the composite hydrogel. The water-holding capacity of the composite hydrogel was enhanced significantly after the addition of oat β-glucan (p < 0.05), which was 18.3 times that of the KGM gel. The thermal stability of KGM gel was enhanced after the addition of oat β-glucan with the increase in Tmax being approximately 30 °C. Consequently, a composite hydrogel based on KGM and oat β-glucan was a strategy to overcome pure KGM gel shortcomings.

A novel and simple gelling system based on a water-soluble copolymer of isobutylene and maleic anhydride (commercial name, Isobam) was adopted to manufacture various ceramics via spontaneous gelation. The gelation mechanism of AlN slurry was investigated using infrared spectroscopy. Results show that Isobam was hydrolyzed to produce the –COOH group, and the hydrogen bonding was formed between the –COOH and –CONH 2 groups of Isobam during spontaneous gelation. Meanwhile, the gelling process of the Isobam system could be accelerated via enhancing hydrogen bonding through APS addition. With 1 wt% addition of APS, the gelation time reduced to 23 h, the viscosity of 50 vol% AlN slurry decreased to 0.21 Pa·s, and the flexural strength of green body improved by 48%. Therefore, the presence of hydrogen bonding in the Isobam gelation mechanism was confirmed, and it could be enhanced by introducing APS to accelerate gelation. [ABSTRACT FROM AUTHOR]

• Self-assembled heat-induced gels had higher mechanical strength. • Hydrophobic interactions had a greater role in self-assembled heat-induced gels. • Self-assembled cold-induced gels had better water retention and dense structure. • Whether or not heat treatment is used to form gels may play a more important role. • Self-assembled cold-induced gels could effectively load bioactive substances. Based on the findings of our previous studies, a comprehensive comparative investigation of the quality and formation mechanism of gels obtained from protein self-assemblies induced by different methods is necessary. Self-assembled heat-induced gels had higher gel mechanical strength, and hydrophobic interactions played a greater role. Whether or not heat treatment was used to induce gel formation may play a more important role than the effect of divalent cations on gel formation. Hydrogen bonds played an important role in all gels formed using different gelation methods. Furthermore, Self-assembled cold-induced gels were considered to can load bioactive substances with different hydrophilicity properties due to the high water-holding capacity and the smooth, dense microstructure. Therefore, β-lactoglobulin fibrous and worm-like self-assembled cold-induced gels as a delivery material for hydrophilic bioactive substances (epigallocatechin gallate, vitamin B 2) and amphiphilic bioactive substance (naringenin), with good encapsulation efficiency (91.92 %, 97.08 %, 96.72 %, 96.52 %, 98.94 %, 97.41 %, respectively) and slow-release performance. [ABSTRACT FROM AUTHOR]

As concern regarding human health, environmental increases, and the need for sustainable food supplies rises, plant proteins are gaining increasingly popularity as alternatives to dairy proteins. The substantial disparity in structural properties and gelation mechanisms between plant proteins and dairy proteins, along with a lack of comprehensive and systematic understanding of their underlying mechanisms under various modification strategies, pose challenges in unlocking the potential substitution of dairy proteins with different plant proteins. The review offers insights into the structure, gelation mechanisms of heat and cold-induced gels of dairy proteins and plant proteins. Furthermore, diverse modification techniques for tailoring the structure of these proteins have been discussed, including chemical, physical, and biological modifications, as well as modifying mechanisms and their advantages and disadvantages. As with whey globular proteins, plant globular proteins usually have compact globular structures and are more prone to heat, making the denaturation of their globular proteins a prerequisite step for gelation. Contrary to globular proteins, casein micelles exhibit flexible random coil structures and good conformational stability to heat in neutral or higher pH but lose stability in acidic conditions. Different modification strategies exhibit diverse mechanisms and peculiarities. Complex coacervation is highly system dependent, while the enzymatic hydrolysis should be controlled in limited degree. Transglutaminase treated gels behave differently when the amount and accessibility of target lysine and glutamine residues differs. Moreover, exploring effective modification strategies for binary plant and dairy proteins to improve their gelation performance can be done in the future. • Structure, gelation modification mechanisms of plant and dairy proteins are reviewed. • Casein differs in structures and gelation mechanisms to whey and plant proteins. • The mechanisms and peculiarities of different modification strategies differ. • Choosing and controlling appropriate modification strategies is essential. [ABSTRACT FROM AUTHOR]

As a versatile ingredient, soy protein isolate (SPI) has been widely used in the food industry and the gelling property of SPI can be further modified using exogenous polysaccharides to achieve desired functionalities and nutritional properties. Therefore, in this study, the effect and mechanism of Lycium barbarum polysaccharides (LBP) on the gelling behavior of soy protein isolate (SPI) were investigated. It was found that the gel strength, water-holding capacity, and viscoelastic properties of SPI gel were improved with the addition of LBP (0.5–2.5%, w/v) in a concentration-dependent manner. Thermogravimetric analysis indicated that the thermal stability of SPI was also improved with the addition of LBP. The FTIR spectroscopy revealed that LBP addition had no significant effect on the α-helix and random coil content of SPI but significantly increased the β-sheet content and reduced the β-turn content. Furthermore, through intrinsic fluorescence, surface hydrophobicity, free sulfhydryl content, and protein solubility analysis, it was concluded that the electrostatic and hydrophobic interactions played a critical role in the formation of the SPI-LBP gel composite. Interestingly, the disulfide bond formation was the least contributor to the binary gel composite network. Overall, LBP is not only an important nutritional supplement but also a promising functional ingredient for improving the gel properties of SPI. [Display omitted] • Lycium barbarum polysaccharides (LBP) enhanced the overall structure of SPI gel. • LBP improved the thermal stability of the soy protein isolate (SPI) gel. • LBP increased β-sheet content of SPI but had a minor effect on α-helix content. • Electrostatic and hydrophobic interactions are critical in the SPI-LBP gel network. [ABSTRACT FROM AUTHOR]

Composed of three-dimensional (3D) nanoscale inorganic bones and up to 99% water, inorganic hydrogels have attracted much attention and undergone significant growth in recent years. The basic units of inorganic hydrogels could be metal nanoparticles, metal nanowires, SiO 2 nanowires, graphene nanosheets, and MXene nanosheets, which are then assembled into the special porous structures by the sol-gel process or gelation via either covalent or noncovalent interactions. The high electrical and thermal conductivity, resistance to corrosion, stability across various temperatures, and high surface area make them promising candidates for diverse applications, such as energy storage, catalysis, adsorption, sensing, and solar steam generation. Besides, some interesting derivatives, such as inorganic aerogels and xerogels, can be produced through further processing, diversifying their functionalities and application domains greatly. In this context, we primarily provide a comprehensive overview of the current status of inorganic hydrogels and their derivatives, including the structures of inorganic hydrogels with various compositions, their gelation mechanisms, and their exceptional practical performance in fields related to energy and environmental applications.

Abstract Network structure and gelation mechanism of kappa carrageenan (KC) and iota carrageenan (IC) were investigated using multiple particle tracking. Based on bulk rheology measurements, KC gels exhibit characteristics of a hard and brittle gel, whereas IC gels form a soft and so-called "weak-gel". Particle tracking revealed the differences in the local physical properties of the two gel systems, which are not accessible with the macroscopic rheological measurements. The mean square displacement (MSD) of the probe particles were investigated to characterize changes in the gel network structure on cooling and storage. On cooling, the MSD of the probe particles in the KC solution decreased drastically at around the gelling temperature, demonstrating the trapping of particles within the network structures of KC gels. The MSD of the probe particles in the IC solution exhibited diffusive behavior even far below the gelling temperature on cooling, although the MSD decreased on storage. These results suggest that KC solutions formed a permanent gel network structure of KC chain aggregates that restricted the motion of particles on cooling. For IC at low temperatures, in contrast, the results suggested two possible structures: 1. clusters of IC chain aggregates, or, 2. a loose network with large pores, which allow the diffusion of particles and lead to weak-gel behavior. The aggregates further aggregate to form a more permanent gel network structure during storage. Graphical abstract Image 1 Highlights • Particle tracking revealed microscopic network structures in carrageenan gels. • IC formed clusters or loose network of IC aggregates allowing diffusion of particles. • Microrheology gave an interpretation for the "weak gel". • Network structure in IC solution changed with storage. [ABSTRACT FROM AUTHOR]

Highlights • Calcium ions improved the gel strength of acid-treated surimi gels to 494.56 g. • The citric acid-added surimi gels had an 85.85% lower lipid content. • Calcium promoted the formation of disulphide and ionic bonds in the gel matrix. • Atomic force microscopy images visualised the myofibril proteins' morphology. • Calcium ion treatment decreased the height of the gelled proteins by 83.33%. Abstract The effect and mechanisms of calcium chloride and citric acid addition on the acid method of processing tilapia protein isolates and surimi gels were studied. The alkaline method shows better gel quality than the acid method with lower yield and high lipid content. The addition of calcium chloride increased the breaking force to 494.56 g and citric acid helped reducing the lipid content by 85.85%, resulting in a higher yield of 75.36%. Gels with calcium maintained low levels of expressible moisture (2.30%), indicating a well-organised gel matrix. The decrease in -SH content and increase in ionic bonds content suggested increased formation of disulphide bonds and ionic bonds. Oscillatory dynamic measurement indicated that more heat resistant bonds were formed. The morphology of myofibril proteins studied by atomic force microscopy (AFM) showed that the height of the proteins in the calcium-added gels decreased 79.4%, which suggested that the protein structure was "suppressed". [ABSTRACT FROM AUTHOR]

Sodium silicate solutions, also known as waterglass, have been found to have remarkable utility in a variety of applications. The cumulative weight of evidence from 70 years of varied analysis indicates that silicate solutions consist of a wide range of species, from monomers through oligomers, up to colloids. Moreover, the structure and distribution of these species are greatly dependent upon many parameters, such as solute concentrations, silica to alkali ratio, pH, and temperature. The most interesting and characteristic property of silicate solutions is their ability to form silica gels. Overall, despite extensive research using different spectroscopic and scattering techniques, many questions related to sodium silicate's dynamic structure, stability, polymerization, and gelation remain difficult to answer. The multitude of simultaneous reactions which restructure the silicate species at the atomic scale in response to variation in solution and environmental parameters, makes it difficult to investigate the individual events using only experimental data. Molecular modelling provides an alternative way to study the unknown areas in the aqueous silicate and silica gel systems, generating key insights into the chemical reactions at microscopic length scales. However, sufficient sampling remains a challenge for the practical use of molecular simulation for these systems. Based on both experimental and modelling studies, this review provides a detailed discussion over the structure and speciation of sodium silicate solutions, their gelation mechanism and kinetics, and the syneresis phenomenon. The goal is not only to review the current level of understanding of sodium silicate solutions, silica gels and characterization techniques suitable for studying them, but also to identify the gaps in the literature and open up opportunities for advancing knowledge about these complex systems. We believe that the future direction of research should be toward correlating atomistic, molecular, and meso-scale level details of interactions and reactions in silicate solution and establishing a fundamental understanding of its gelation mechanism and kinetics. We believe that this knowledge could eliminate the "trial and error" approach in manufacturing, and improve structural control in the synthesis of important materials derived from these solutions, such as silica gels and zeolites. [Display omitted] • Review of factors affecting sodium silicate solution's speciation and gelation. • Visualization of chemical structure of sodium silicate solutions and gels. • A general theory of silica gelation modified for sodium silicate solutions. • Molecular modelling provides atomistic insight into complex silica-water reactions. • Insights illustrate the need to advance our understanding of silica-water systems. [ABSTRACT FROM AUTHOR]

Sugarcane molasses (SCM), a byproduct generated from sucrose manufacturing, has attracted considerable interest due to its high sugar content, polyphenolic compounds, and calcium ions. The objective of this study was to fabricate a type of low methoxy pectin (LMP)-based gel crosslinked by endogenous calcium ions found in SCM. Gel was formed by adding SCM into a 1 wt% LMP solution, which resulted in a Ca2+ concentration of 2–6 mmol/L. Rheological and textural measurements confirmed the formation of SCM-LMP gels. Compared to LMP gels induced by CaCl 2 , SCM-LMP gels exhibited weak storage modulus and gel strength, probably due to the presence of metal ions and small molecular sugars from SCM, which impede the formation of effective junction zones required for building a calcium-pectin network. The polyphenolic compounds from SCM were encapsulated within the SCM-LMP gel, enhancing its antioxidant capacity. Overall, this research explores the effectiveness of SCM in inducing LMP gelation for the first time. The findings of this study demonstrate a strategy for preparing LMP gels with antioxidant properties. • Sugarcane molasses (SCM) induced the gelation of low-methoxy pectin (LMP). • Endogenous calcium ions of SCM crosslinked LMP into gels. • SCM-LMP gels displayed antioxidant properties. • SCM dosage regulated viscoelastic and textural properties of LMP [ABSTRACT FROM AUTHOR]

Various polymers are the most widely used product to provide rheology for water-based fracturing fluid, however, they have weaknesses in terms of temperature resistance and salt resistance. The change from organic-based to inorganic thickeners may be a meaningful attempt. Inorganic silica gel is a potentially alternative viscosifier with high temperature resistance, excellent proppant carrying capacity, and can even be used to prepare fracturing fluids with high salinity of produced water. In this paper, the silica gel viscosifier was firstly prepared using sol–gel method. Then, the gelation time under different influencing factors and rheological properties of the silica gel viscosifier were studied in detail. Subsequently, the silica gel-based fracturing fluid was prepared by adding the desired amount of drag reducer to the silica sol solution, and the properties of novel fracturing fluid were systematically evaluated with regard to the temperature and shearing resistance, drag reduction, and static proppant suspension. The potential mechanism of gelation process by syneresis of silica gel was revealed at last. Results showed that the microstructure of silica gel is synthetic, amorphous and consists of a three-dimensional network of SiO 2 particles. The effect of SiO 2 concentration on the gelation time is more pronounced than other factors such as temperature and pH level. In addition, the silica gel viscosifier exhibits strong salt resistance, whether monovalent ions (Na+, K+) or divalent ions (Ca2+, Mg2+), and the gelation time decreased significantly with the increase of salt concentration. The shear viscosity of the silica gel viscosifier increased with an increase of SiO 2 concentration, showing shear thinning behavior as well. Meanwhile, the silica gel-based fracturing fluid prepared by adding drag reducer into silica sol solution also presented excellent thermal stability and shear resistance, drag reduction and proppant suspension performances. The retained viscosity can be maintained above 50 mPa·s after shearing at 180 °C for 60 mins; the drag reduction rate shows a declining trend at high displacement due to the gelation process; the settling rate of 40/70 mesh sand proppant with 35 % sand ratio is less than 30 % after standing at 90 °C for 4 h. In addition, the gelation process is essentially the formation of Si-O-Si linkage by dehydration between SiO 2 particles, which is gradually extended at both ends and sides of the chain, and eventually forms a rigid, highly porous, entangled network. Findings found in this study provide a research basis for the popularization and application of silica gel-based fracturing fluid. [ABSTRACT FROM AUTHOR]

Pectin modification is an effective approach for changing its functional properties and discovering new applications. To provide more insight into the modified pectin structure-function relationships, tyramine (Tyr) modified high (HMP) and low methoxylated pectin (LMP) were prepared to construct novel pectin gel systems. FTIR, 1H NMR, and UV–vis analyses confirmed that Tyr groups were successfully grafted onto pectin chain and obtained the unreacted galacturonic acid (GalA) content. Physiochemical characterization revealed that Tyr modified pectin exhibited enhanced solubility, amphiphilicity and antioxidant activity. Tyr modified pectin gels possessed good viscoelastic property, but obviously decreased elasticity and strength compared to native pectin gel. Entanglement network number (ENN) and scanning electron microscopy (SEM) image demonstrated the decreased internal cross-linking networks density which contributed to the altered gelling properties of Tyr modified pectin gels. The proposed gelling mechanism indicated that bulky Tyr involved physical interactions were mainly responsible for the changed pectin gelling behavior and gelation process in nature. Similarly, the textural properties and water holding capacity (WHC) of Tyr modified pectin gels were closely related to their physical interaction categories and gelling network microstructure. Sucrose induced gellation of the Tyr modified LMP with strong carboxyl groups related hydrogen bonding showed higher hardness. Calcium ions induced gellation of the Tyr modified LMP formed a larger porous gel matrix which resulted in a poor WHC. The findings provide theoretical basis on physicochemical properties and gelling behaviors of Tyr modified pectin for expanding their application in the fields of food preservation, emulsifiers, stabilizers, and tunable gel-type foods. [Display omitted] • High (HMP) and low methoxylated pectin (LMP) was modified by Tyramine (Tyr). • Tyr modification resulted in enhancement of solubility and antioxidant activity of pectin. • Gelling properties of Tyr modified pectin gel were dependent on physical interactions. • Gelation mechanism is related to both physical interactions and entangled networks. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the chemical composition, molecular weight (Mw), and monosaccharide composition of Premna microphylla Turcz polysaccharide (PMP) and revealed the effects of calcium ions (Ca2+) on the rheological properties, thermal stability, texture properties, and structural properties of PMP gels. Additionally, the gelation mechanism of PMP was proposed. The results revealed that PMP was a negative charge acidic polysaccharide primarily composed of glucose, galactose and rhamnose. The results of small and large amplitude oscillatory shear experiments illustrated that the storage modulus (G′), loss modulus (G″), relaxation modulus (G(t)) of PMP gels showed a positive correlation with Ca2+ concentration, indicating the addition of Ca2+ improved the viscoelasticity and shear thinning capacity of PMP gels. Furthermore, the gel strength, hardness, and thermal stability of PMP gels were enhanced with increase of Ca2+ concentration. The microstructure of PMP gel was changed obviously after adding Ca2+, generating the lamellar and lump-like structure due to the PMP aggregation. The results of Zeta potential, X-ray diffraction, and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that electrostatic interactions played a crucial role in the formation of PMP gel and three-dimensional structure. These results suggested that PMP had great potential for application in the food industry due to their excellent gelation properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Macroporous gels find application in several scientific fields, ranging from art restoration to wastewater filtration or cell entrapment. In this work, two-component sponge-like cryogels are challenged to assess their cleaning performances and to investigate how pores size and connectivity affect physico-chemical properties. The gels were obtained through a freeze-thaw process, exploiting a spontaneous polymer-polymer phase-separation occurring in the pre-gel solution. During the freezing step, a highly hydrolyzed polyvinyl alcohol (H-PVA) forms the hydrogel walls. The secondary components, namely a partially hydrolyzed polyvinyl alcohol (L-PVA) or polyvinyl pyrrolidone (PVP), act as modular porogens, being partially extracted during gel washing. H-PVA/L-PVA and H-PVA/PVP mixtures were studied by confocal laser scanning microscopy to unveil sols and gels morphology at the micron-scale, while small angle X-ray scattering was used to get insights about characteristic dimensions at the nanoscale. The gelation mechanism was investigated through rheology measurements, and the characteristic exponents were compared to De Gennes' scaling laws gathered from percolation. In the field of art conservation, these sponge-like gels are ideal systems for the cleaning of artistic painted surfaces. Their interconnected pores allow the diffusion of cleaning fluids at the painted interface, facilitating dirt uptake and/or detachment. This study uncovered a direct relationship linking a gel's cleaning performance to its apparent tortuosity. These findings can pave the way to fine-tuning systems with enhanced cleaning abilities, not restricted to the restoration of irreplaceable priceless works of art, but with possible application in diverse research fields.

In this work, the gelation mechanism of graphene quantum dots (GQDs) into hydrogels is investigated using dynamic light scattering and ultraviolet-visible techniques. Hydrogels are prepared through the hydrothermal reduction of concentrated GQDs solutions (20–50 mg/mL) using l -ascorbic acid as the reducing agent. At early stages of the gelation process (first 2 h), J-type aggregation of GQDs results in the formation of particles with dimensions around 10 nm. As the gelation process proceeds, formation of larger particles through the aggregation of almost all GQDs results in slower dynamics and hindered Brownian motions in the solution. With the reduction of a majority of edge-carboxyl groups through six first hours of the hydrothermal process, a change in the self-assembly mechanism takes place (from J-type to H-type). A GQDs hydrogel, with an interconnected colloidal morphology and a very low density (~0.009 g/cm 3 ) can be obtained after 8 h of the hydrothermal process. The specific surface area of the prepared GQDs hydrogel, fabricated through the hydrothermal reduction of the 20 mg/mL GQDs precursor solution, is >1000 m 2 /g. Hydrogels and cryogels prepared using GQDs as the building units can be applicable where hyper-porous structures with large number of available sites are needed. [ABSTRACT FROM AUTHOR]

Polysaccharide-based hydrogels were prepared by the diffusion of various divalent cations (X 2+ ) into the polygalacturonate (polyGal) solution through a dialysis membrane. The diffusion of various divalent cations (Mg 2+ , Ca 2+ , Zn 2+ and Ba 2+ ) was investigated. The polyGal gel growth was studied as a function of the initial cation concentration by both viscoelastic and turbidity measurements. We have demonstrated for the first time that the determination of the spatiotemporal variation of turbidity during the gelation process allowed to study the gel front migration. For Ca-polyGal, Zn-polyGal and Ba-polyGal, the gel front migration was characterized by the presence of a peak at the sol/gel interface. This peak was not observed in the case of Mg-polyGal where the gel was not formed. The apparent diffusion coefficient of the gel front (D app ) which was calculated from the evolution of this peak increased when the initial cation concentration was increased. Moreover, we have suggested a gelation mechanism based on the presence of a threshold molar ratio R* (=[X 2+ ]/[Galacturonic unit]) in which some point-like crosslinks are precursors of the formation of dimers and multimers inducing the contraction of the gel and thus the formation of the gel front. [ABSTRACT FROM AUTHOR]

We designed stable and highly reproducible hydrogels by external unidirectional diffusion of Fe 2+ ions into aqueous solutions of polygalacturonate (polyGal) chains. The Fe 2+ ions act as cross-linkers between the Gal units in such a way that both the molar ratio R ([Fe 2+ ]/[Gal units] = 0.25) and the mesh size of the polyGal network at the local scale (ξ = 75 ± 5 Å) have constant values within the whole gel, as respectively determined by titration and Small Angle Neutron Scattering. From macroscopic point of view, there is a progressive decrease of polyGal concentration from the part of the gel formed in the early stages of the gelation process, which is homogeneous, transparent and whose Young modulus has a high value of ∼10 5  Pa, up to the part of the gel formed in the late stages, which is heterogeneous, highly turbid and has a much lower Young modulus of ∼10 3  Pa. Since the local organization of the polyGal chains remains identical all along the hydrogels, this macroscopic concentration gradient originates from the formation of heterogeneities at a mesoscopic length scale during the gelation process. In addition, X-ray Absorption Spectroscopy measurements remarkably reveal that Fe 2+ ions keep their +II oxidation state in the whole gels once they have cross-linked the Gal units. These polyGal hydrogels thus protect iron against oxidation and could be used for iron fortification. [ABSTRACT FROM AUTHOR]

In the current study, dynamic frequency sweep and stress relaxation tests were performed to elucidate the possible gelation mechanisms of a unique thermal stable polysaccharides from Auricularia auricula-judae (AP). Addition of NaCl, CaCl 2 and Ca-chelating agent (EDTA) to AP confirmed that electrostatic interaction was not the deciding force in forming the network of AP dispersion and the intrinsic calcium of AP played a role of inhibition in AP network formation. Addition of the hydrogen bond breaking agent, urea, highlighted the important role of hydrogen bonding in the formation of gel networks. The results suggested that carboxyl group of the uronic acid on AP chain are involved in the formation of inter/intra hydrogen bonding which maintain AP gel network. Quantitative effect of concentration, pH, urea and glucuronic acid on the network structure of AP dispersion were also be evaluated by entanglement network numbers (ENN) based on stress relaxation. [ABSTRACT FROM AUTHOR]