Form Gel Networks Research Articles

Novel chitosan-enhanced alkali-activated material for remediation of zinc-contaminated coastal mudflat sediment

Sustainable utilization and development for contaminated mudflat sites face dual challenges associated with contaminant enrichment and engineering diseases, impacting ecological quality and coastal construction. Commonly used cement has limitations in ensuring geo-environmental engineering performances for polluted sediments. This study investigates a solidification/stabilization approach using novel chitosan-enhanced alkali-activated material (CTS-AAM) to remediate highly concentrated zinc-contaminated sediments. Results exhibit that the compressive strength and water stability of sediments are remarkably improved by CTS-AAM, satisfying engineering service even under long-term immersion and zinc accumulation. Significant improvements dependent on curing period and CTS-AAM dosage also reflect in the resistance to deformation of remediated sediments, maintaining low-compressibility states due to the enhancement of structural yield stress. The leaching toxicity of remediated sediments meets Zn ≤ 5.0 mg/L, as zinc primarily distributes to the residual fraction associated with low mobility. The bidirectional enhancement of toxic sediment is attributed to the generation of hydrates with cementitious and pore-filling effects through hydration reactions. Simultaneously, chitosan with hydrated gels and ettringite collectively form gel networks and compact skeleton structures within sediments, as well as immobilize Zn through comprehensive physical encapsulation, chemical binding, and chelation. This study provides a feasible strategy for future projects involving remediation and utilization of mudflats.

Exploring the relationship between starch structure and physicochemical properties: The impact of extrusion on highland barley flour

Highland barley (HB) is an intriguing plateau cereal crop with high nutrition and health benefits. However, abundant dietary fiber and deficient gluten pose challenges to the processing and taste of whole HB products. Extrusion technology has been proved to be effective in overcoming these hurdles, but the association between the structure and physicochemical properties during extrusion remains inadequately unexplored. Therefore, this study aims to comprehensively understand the impact of extrusion conditions on the physicochemical properties of HB flour (HBF) and the multi-scale structure of starch. Results indicated that the nutritional value of HBF were significantly increased (soluble dietary fiber and β-glucan increased by 24.05%, 19.85% respectively) after extrusion. Typical underlying mechanisms based on starch structure were established. High temperature facilitated starch gelatinization, resulting in double helices unwinding, amylose leaching, and starch-lipid complexes forming. These alterations enhanced the water absorption capacity, cold thickening ability, and peak viscosity of HBF. More V-type complexes impeded amylose rearrangement, thus enhancing resistance to retrogradation and thermal stability. Extrusion at high temperature and moisture exhibited similarities to hydrothermal treatment, partly promoting amylose rearrangement and enhancing HBF peak viscosity. Conversely, under low temperature and high moisture, well-swelled starch granules were easily broken into shorter branch-chains by higher shear force, which enhanced the instant solubility and retrogradation resistance of HBF as well as reduced its pasting viscosity and the capacity to form gel networks. Importantly, starch degradation products during this condition were experimentally confirmed from various aspects. This study provided some reference for profiting from extrusion for further development of HB functional food and “clean label” food additives.

Performance characteristics of micro fiber-reinforced ambient cured one-part geopolymer mortar for repairing

The development of one-part geopolymer mortars has greater potential than the traditional two-part mortars, especially in repair applications, to convert waste into useful beneficial products while simultaneously eliminating the hazards associated with the alkaline solutions. Nevertheless, the inherent brittleness exhibited by the one-part geopolymers displays drawbacks like OPC when subjected to flexural loading. The fibers selection as well as their strengthening effects from literature is considerably scarce, especially for the repairing geopolymer system. This work aims to investigate the influences of fiber types and volume fractions on the workability, physical behavior, and cracking/fatigue resistance of ambient air-cured one-part geopolymer mortar. Reaction kinetics, mineralogical phases, and elemental components were explored by means of the TAM, quantitative XRD, and EDS mapping analysis. The FESEM and X-CT were employed to compare the microstructures and pore characteristics of the fibers-reinforced products. The results show that the copper-plated steel fiber produced the least change in workability, while the basalt fiber produced the lowest flow values. Setting time was the shortest for the basalt fiber reinforced, followed by polyvinyl-alcohol fiber. The steel fiber and carbon fiber would improve the mechanical properties of mortar significantly, especially in the early stage. The fatigue strength of 1 vol% carbon fiber reinforced mortar under 2 million cycles loading was the highest (3.72 MPa). The fibers addition a substantial decrease in sphericity and compactness of the pores (high anisotropy) as evidenced by X-CT data. Moreover, three hydration heat processes occurred after water was added to the one-part geopolymer mortar, which included dissolution of Na2SiO3 particles, network degradation, and a second pozzolanic reaction. More crystalline formation occurred over curing time to form gel networks with high stability and generated different bonding modes with various fibers.

Rheological Properties and Kinetics of Gelation of Binary Polymers between Xanthan Gum and Locust Bean Gum.

The synergistic interaction and gelling kinetics between xanthan gum (XG) and locust bean gum (LBG) at different mass ratios (XG/LBG 9:1, 7:3, 5:5, 3:7, 1:9) were investigated using a rheometer. The results showed that the mixtures of XG and LBG induced gel formation, and the strongest gel structure was found for the mixture of XG/LBG 3:7 according to the yield stress, storage modulus (G'), and power law parameters. Temperature ramp studies indicated that heating destroyed the gels at 55~60 °C, while cooling induced the sol-gel transition at around 52 °C for all mixtures. Structure developing rate (SDR) curves showed that XG/LBG 3:7 exhibited the highest SDR during the cooling ramp among all the samples. Non-isothermal kinetic analysis demonstrated that the gelation process of XG/LBG mixtures during cooling included two steps: a high-temperature region (55~39 °C) needing higher activation energy (Ea, 111.97 to 199.20 kJ/mol for different mixtures) and a low-temperature region (39~20 °C) needing lower Ea (74.33 to 85.31 kJ/mol), which indicated higher energy barriers to overcome at the initial stage of gel formation. The lowest Ea of 74.33 kJ/mol was found for XG/LBG 3:7 in the low-temperature region. Scanning electron microscopy (SEM) showed that the gel of XG/LBG 3:7 presented the densest entanglements. These results indicated the strongest synergism interaction occurred in XG/LBG 3:7 to form gel network structures. This study will help promote the application of XG-LBG blends to design novel food structures.

Advancing Quantification of Water-Extractable Arabinoxylan in Beer: A High-Throughput Approach.

Water-extractable arabinoxylan (WEAX) may cause major problems during clarification processes in a brewery owing to its ability to form gel networks. However, high WEAX contents can also enhance the nutritional quality of the final product as they play an important role in the human diet. Therefore, precise quantification of WEAX is required. Current methods are very time- and resource-consuming as well as limited in the number of samples and in some cases provide low accuracy. Thus, a reproducible high-throughput method for the quantification of WEAX optimized for beer was developed, reaching recovery rates (RRs) of almost 100%. The assay is based on Douglas's colorimetric method. Hydrolysis was conducted using glacial acetic acid to induce the formation of red color complexes resulting from the interaction between pentose degradation products and phloroglucinol. The method was successfully transferred to a multi-mode microplate reader to minimize the loss of color intensity over time and to obtain a high throughput. By using 96-well plates, up to 40% of the previous analysis time could be saved, and a larger number of samples could be analyzed in one batch. The collected data determined xylose as an optimal calibration standard due to high accuracy and reproducibility. The respective AX control standards showed RR within the range of 95-105% without exception. To validate and show the ruggedness of the modified method, WEAX concentration in seven commercial German beers (e.g., lager, pilsner, wheat beer, non-alcoholic beer) was quantified. Interfering hexose sugars that lead to measurement errors when analyzing samples with high amounts of fermentable sugars (e.g., non-alcoholic beer produced by limited fermentation) were eliminated by Saccharomyces diastaticus fermentation. Further investigations were carried out by means of LC-MS in order to obtain additional information about the reddish product in the hydrolyzed samples. In this context, C16H12O6 could be identified as one of numerous condensation products, contributing to the coloring. The collected data showed the impact of diverse factors on the measured AX concentration and helped optimize the experimental procedure for a high sample throughput with precise and highly reproducible results. The proposed quantification method should be primarily used in completely fermented finished beer to emphasize the time aspect. Wort samples and non-alcoholic beer produced by limited fermentation can be also analyzed, but only after fermentation with S. diastaticus.

Destabilization of oil-in-water emulsions: Influences of interfacial assembly of octenyl succinic anhydride starch and chitosan

This study investigated the formation and destabilization of emulsions with different interfacial assemblies of octenyl succinic anhydride starch (OSAS) and chitosan (CS) at critical pH values. All emulsion droplets were connected to each other via bridging of interfacial percolation and observed to form gel network structures during prolonged storage. In addition, partial pH-dependent flocculation occurred during preparation and decreased the degree of coalescence and creaming of emulsions. Compared to bilayer (OSAS-CS and CS-OSAS) emulsions, the complex (OSAS/CS)-stabilized emulsions were more resistant to coalescence, creaming, and lipid oxidation because of their thick interfacial layers (∼2 μm) and tight percolation networks. The layer-by-layer adsorption of OSAS and CS at the interface may lead to reduced homogeneity and stability of the bilayers, making them relatively susceptible to destabilization. Moreover, an appropriate pH (6.0) facilitated the oxidation stability of emulsions by influencing inter-droplet electrostatic interactions. For complex-stabilized emulsions, the lipid hydroperoxide content at pH 6.0 was reduced by approximately 22.85% and 12.26% respectively compared with that at pH 5.5 and pH 6.5. This work may provide promising insights into the rational design of emulsions with desirable stability by combing biopolymers.

An N,P,O-doped porous carbon electrode material derived from a lignin-modified chitosan xerogel for a supercapacitor

Lignin is a promising candidate for obtaining porous carbon materials for energy storage because it has the highest carbon content compared with the other two main components. While it is the main challenge to realize the high electrochemical performance by controlling the pore structure and improving the conductivity of carbon materials. In the present study, lignin was introduced into a chitosan solution after being chemical activated by degradation liquefaction to form a gel network with the introduction of β-glycerophosphate as a cross-linking agent. In this procedure, the formed gel network provided a basic porous structure for further obtaining highly porous carbon after the following carbonization and activation. In the same procedure, N, P, and O heteroatoms were doped in, which were efficiently preserved in the final derived porous carbon to produce the polar hierarchical porous carbon. The prepared porous carbon under optimized conditions achieved a high specific area of 2107.3 m2/g, with an average pore diameter of 3.63 nm. A high specific capacity of 534.9 F/g at a current density of 1 A/g was obtained. Simultaneously, the coin-type symmetric supercapacitors (with an ionic liquid electrolyte) based on the derived carbon also exhibit an outstanding energy density (58 Wh/kg at 375 W/kg and 11.5 Wh/kg at 4500 W/kg). This work explored an effective strategy for the application of the lignin resource in the field of energy storage materials.

Enhancing viability of Lactobacillus plantarum encapsulated by alginate-gelatin hydrogel beads during gastrointestinal digestion, storage and in the mimic beverage systems

To improve the viability of Lactobacillus plantarum (P) during digestion and storage, the probiotics were encapsulated by alginate (ALG) and alginate-gelatin (ALG-GE) hydrogels beads. ALG-P-GE showed much better physicochemical properties than ALG-P. The scanning electron microscopy (SEM) results validated the incorporation of bacterial cells into the beads. ALG-P-GE exhibited good encapsulation efficiency of 97.7 %, and the storage and thermal stability of probiotic were increased by 15 % and 8 %, respectively, when comparing with ALG-P. ALG-P-GE beads could protect the probiotics from inactivation in simulated gastric fluid and then release it in simulated intestinal fluid. The protective mechanism of ALG-GE for probiotics was further studied by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and found that ALG and GE can form gel network through hydrogen bonding and electrostatic interactions. In the mimic beverage systems, ALG-P-GE beads could protect the encapsulated probiotics and increase its viability. The storage, thermal, and digestion stability of encapsulated probiotic were significantly increased and showed high viability in the mimic beverage systems. ALG-P-GE beads have great potential for the protection and delivery of probiotics in food systems.

CO2 induced gelation of amidated pectin solutions: Impact of viscosity and gel formation

CO2 induced gelation of aqueous biopolymer systems results in stable and homogeneous hydrogels with a wide field of potential applications in food and pharmaceutical industry. For the application of the process in industry, good understanding of process parameters and their impact on the overall process and the gel properties is necessary. The mechanism of the CO2 induced gelation is not fully understood; the role of viscosity has never been addressed in the literature. The first step of the overall gelation process, the dissolution of CO2 into the biopolymer systems, is limiting for the overall process. Therefore, it was investigated in this work with different non-invasive, in-situ measurement methods: magnetic suspension balance and Raman spectroscopy on the system of amidated pectin with calcium carbonate (CaCO3) as additional cross-linker. With increasing viscosity of the biopolymer system, due to increasing amidated pectin mass fraction, the CO2 dissolution is slowed down. For non-gelling, CaCO3-free biopolymer systems effective diffusion coefficients from 17.7·10-9 to 5.6·10-9 m2/s were determined for solutions with increasing complex viscosities from 0.011 to 0.379 Pa s (0.5 to 2 wt.-% amidated pectin). In this case, the effective diffusion coefficient considers mass transport due to pure diffusion and due to free convection. Inside the non-gelling biopolymer systems, free convection appears and no gradient of the CO2 concentration inside the samples occurs. Nevertheless, in gelling, CaCO3 containing, biopolymer systems the formation of the gel network (gelation) itself has a strong impact on CO2 dissolution, as it hinders free convection. Due to gelation, the effective diffusion coefficient is decreased down to about 2.5·10-9 m2/s and approaches the binary diffusion coefficient of CO2 in water; indicating pure diffusion of CO2 in pores that contain mainly pure water. At 50 bar and room temperature CO2 solubility of 0.043 ± 0.003 g of CO2 per gram of the aqueous system, nearly independent of solution composition and gelation was measured. Contrarily, increasing temperatures as well as decreasing pressure results in decrease of overall CO2 solubility, whereas increasing temperature does enhance dissolution and distribution kinetics. With the performed measurements, it was possible to distinguish between the impacts of viscosity, gelation, and the formed gel network on the CO2 dissolution kinetics inside the sample, respectively.

Hydro- and aerogels from ethanolic potato and whey protein solutions: Influence of temperature and ethanol concentration on viscoelastic properties, protein interactions, and microstructure

Denaturation, aggregation, and gelation of protein solutions can be induced through increased temperatures and the presence of organic solvents. Depending on the molecular features of the involved proteins, the denaturation conditions lead to very different gel properties. However, it is poorly understood how organic solvents in combination with heat treatments can be used to modify the textural properties of protein gels. In this study, the combined effects of heat and ethanol (EtOH) treatment on hydrogel formation by whey (WPI) and potato protein isolates (PPI) were investigated. The different protein hydrogels were subjected to a complete solvent exchange with EtOH and dried with supercritical CO2 to obtain aerogels with a high inner surface area. Increasing EtOH concentration during thermally induced hydrogel formation reduced the temperature of unfolding up to a point where denaturation occurred at room temperature. WPI and PPI formed very different gels in the presence of EtOH. WPI gels with an EtOH content below 10% (w/w) were elastic and mainly linked through disulfide bonds. Higher EtOH content led to weak gels, mainly linked through electrostatic and hydrogen bonds. For PPI gels, increasing EtOH content did not influence the protein interactions within the gels, and textural properties were very similar. The textural properties of the resulting aerogels were dependent on the type of protein interactions created in the hydrogels. This work provides insights into the way food proteins form gel networks and how these interactions can be manipulated to produce gels with tailor-made properties.

Dual cryoprotective and antioxidant effects of silver carp (Hypophthalmichthys molitrix) protein hydrolysates on unwashed surimi stored at conventional and ultra-low frozen temperatures

The dual cryoprotective and antioxidant effects of silver carp hydrolysates on unwashed surimi, stored at conventional (−18 °C) or ultra-low (−60 °C) temperatures and subject to three and six freeze-thaw treatments, were examined. The addition of hydrolysates could alleviate the formation of carbonyls of myofibrillar protein, inhibit the decrease of free sulfhydryl content and keep the protein bands stability compared to the control and SuSo group. The lipid peroxidation product malondialdehyde, and the target volatiles hexanal, nonanal and 1-octen-3-ol of the unwashed surimi as detected by HS-SPME-GC-MS, increased slowly under the protection of hydrolysates. The oxidation for proteins and lipids in freeze-thawed samples stored at −18 °C are lower than those of samples stored at −60 °C (p < 0.05), indicating that ultra-low frozen temperature storage accompanied by freeze-thaw cycles accelerates structural deterioration of unwashed surimi. LF-NMR and SEM also revealed that the hydrolysates facilitated to form gel network with preferable structural integrity and stability during freeze-thaw treatments. This study provides theoretical supports for the application of silver carp protein hydrolysates as a cryoprotectant in transportation and storage of frozen surimi.

Gelation and network structure of acidified milk gel investigated at different length scales with and without addition of iota-carrageenan

This work investigated the formation of acid milk gel at different length scales with and without the addition of iota-carrageenan (IC) (0.5% w/w) during incubation at 30 °C, using bulk rheology and syringe compression test at the macroscopic level, passive particle tracking (particle diameter 0.3 μm and 1.0 μm) at the microscopic level and pulsed field gradient (PFG)-NMR with poly(ethylene oxide) (PEO) at the molecular level. IC induced the early formation of the gel network in the sample as demonstrated by the progressive G′ and G″ increase (where G′ > G″) in the macroscopic measurement. When repeatedly compressed at the developing stage, the formed gel network in the IC sample reassociated into non-native colloidal structures unable to contain the serum phase, which also occurred without IC but at later incubation stage. The increased PEO diffusion at 30 min in PFG-NMR reflected the emerging casein-casein network and its extensive rearrangement occurring at the molecular level in both samples. This corresponded with the mean square displacement of the probe particles with IC at 30 min but not without IC, indicating that IC altered the length scale of the network rearrangements occurring at the molecular level to be detected at the microscopic level in the particle tracking. The size-dependent particle behaviors in the particle tracking demonstrated a high degree of IC-induced network heterogeneity that continued to develop even at late incubation stage, on contrary to the drastic compaction of the formed network observed in the sample without IC.

Recent Advances in Food Emulsions and Engineering Foodstuffs Using Plant-Based Nanocelluloses.

In this article, the application of nanocelluloses, especially cellulose nanofibrils and cellulose nanocrystals, as functional ingredients in foods is reviewed. These ingredients offer a sustainable and economic source of natural plant-based nanoparticles. Nanocelluloses are particularly suitable for altering the physicochemical, sensory, and nutritional properties of foods because of their ability to create novel structures. For instance, they can adsorb to air-water or oil-water interfaces and stabilize foams or emulsions, self-assemble in aqueous solutions to form gel networks, and act as fillers or fat replacers. The functionality of nanocelluloses can be extended by chemical functionalization of their surfaces or by using them in combination with other natural food ingredients, such as biosurfactants or biopolymers. As a result, it is possible to create stimuli-responsive, tailorable, and/or active functional biomaterials suitable for a range of foodapplications. In this article, we describe the chemistry, structure, and physicochemical properties of cellulose as well as their relevance for the application of nanocelluloses as functional ingredients in foods. Special emphasis is given to their use as particle stabilizers in Pickering emulsions, but we also discuss their potential application for creating innovative biomaterials with novel functional attributes, such as edible films and packaging. Finally, some of the challenges associated with using nanocelluloses in foods are critically evaluated, including their potential safety and consumer acceptance.

Effect of interfacial compositions on the physical properties of alginate-based emulsion gels and chemical stability of co-encapsulated bioactives

Alginate-based emulsion gels with different oil fraction (0–20%) and interfacial compositions were developed to understand the filling roles of oil droplets, and the gels were used to simultaneously encapsulate a lipophilic and a hydrophilic bioactives. Glucono-delta-lactone (GDL) was used to induce the release of Ca2+ from CaCO3, which allowed the cross linking of alginate to form gel network and trap the oil droplets. The increase in oil fraction significantly reduced syneresis degree and improved water holding capacity (WHC) of the emulsion gels with tween 20 (TW), negatively charged WPI (-/WPI), whey protein aggregates (WPA) at the interface. Significantly increased fracture force was observed in the emulsion gels with positively charged WPI (+/WPI) with the increase in oil fraction. In the systems containing TW, -/WPI or WPA, the inclusion of oil phase mostly resulted in lower fracture force than the systems without oil. However, all the systems had higher relaxed stress (at equilibrium) with higher oil content. Swelling tests revealed that the systems with an oil content of 10% had the highest swelling ratio, and the gels containing +/WPI had the lowest swelling ratio among all the systems. When EGCG and β-carotene were encapsulated within the emulsion gels, they presented a synergistic effect on heating stability as both EGCG and β-carotene had higher stability when encapsulated simultaneously than individually.

Influence of two functional dextrins on the gel properties of kappa-carrageenan

The physicochemical properties of κ-carrageenan (KC) can be improved by incorporation with small-molecule cosolvents. The texture and rheological properties, micromorphology, and crystallinity of KC incorporating indigestible dextrin (IDD) and beta-limit dextrin (BLD) were investigated. The rheological properties and sol-gel transition temperatures of the gels were slightly improved and the hardness of KC gels was significantly increased after the two dextrins were mixed in. Fourier transform infrared spectroscopy results indicated hydrogen-bonding interactions were strengthened in the presence of the dextrins. Confocal laser scanning microscope images revealed that a more homogenous structure was formed of the KC gel after the addition of dextrins. Moreover, X-ray diffraction patterns indicated the crystallinity of KC gel decreased upon dextrin addition. At the same dextrin content, IDD exerted a greater influence than BLD. IDD contents exceeding 3% (w/w) led to undesirable effects, whereas up to 5% (w/w) of BLD could be added. The two dextrins affected the rearrangement of the KC random coils in the sol state, and facilitated aggregation of the KC chains during cooling to form gel network structures after gelation. Therefore, the appropriate addition of these two dextrins can improve the texture and stability of KC gels and expand their application in functional foods.

Effect of preheating-induced denaturation during protein production on the structure and gelling properties of soybean proteins

To explore the effect of preheating-induced denaturation during protein production on the structure and gelling properties of soybean protein isolates (SPI), protein neutralization solutions were preheated at various temperature for various periods and then spray-dried. The pre-denaturation degree (PDD) of SPI was quantitatively characterized by the change in the AB subunit using non-reducing SDS-PAGE. The onset denaturation time was 180 s, 40 s, and 10 s at preheating temperatures of 80 °C, 90 °C and 100 °C. As PDD increased, the contents of free sulfhydryl group and the ordered secondary structure gradually decreased, accompanied by the unfolding of the tertiary structure. Gel hardness, G′ and G″ increased at high PDDs, where the heating time required for gel formation decreased. The highly pre-denatured proteins (e.g., SPI86.11%, and SPI100%) formed gel network structures without heating. SEM images showed that the partially pre-denatured gels (SPI22.28% and SPI86.11%) were denser and had more uniform gel networks than the native protein (SPI0) and the completely pre-denatured protein (SPI100%). This work will provide guidelines for the control of heating conditions during SPI production process to improve gelling properties.

Distribution of short to medium amylose chains are major controllers of in vitro digestion of retrograded rice starch

In many cultures, rice is let to cool for a while after cooking before being consumed, which results in some retrogradation of the starch. The in vitro digestibility of 16 cooked rice starches after extended cold (4 °C) storage, which leads to extensive retrogradation, was investigated from the perspective of their starch molecular fine structure. Size-exclusion chromatography (SEC) and fluorophore-assisted carbohydrate electrophoresis (FACE) were used to characterize the starch chain-length distributions (CLDs) and whole molecular size distributions. The retrograded starch gel network was studied by differential scanning calorimetry and scanning electron microscopy. Pearson correlation analysis with in vitro digestibility revealed that the starch digestion rate was positively correlated with cell size and cell wall thickness within the formed gel network, which was mainly derived from the interactions of amylose short-medium chains and not strongly related to amylopectin molecular structure. This suggests that rather than just altering amylose content, modification of amylose fine molecular structure (e.g. increasing the amount of short-medium amylose chains) can also slow rice starch digestibility.

Supramolecular Amino Acid Based Hydrogels: Probing the Contribution of Additive Molecules using NMR Spectroscopy.

Supramolecular hydrogels are composed of self‐assembled solid networks that restrict the flow of water. l‐Phenylalanine is the smallest molecule reported to date to form gel networks in water, and it is of particular interest due to its crystalline gel state. Single and multi‐component hydrogels of l‐phenylalanine are used herein as model materials to develop an NMR‐based analytical approach to gain insight into the mechanisms of supramolecular gelation. Structure and composition of the gel fibres were probed using PXRD, solid‐state NMR experiments and microscopic techniques. Solution‐state NMR studies probed the properties of free gelator molecules in an equilibrium with bound molecules. The dynamics of exchange at the gel/solution interfaces was investigated further using high‐resolution magic angle spinning (HR‐MAS) and saturation transfer difference (STD) NMR experiments. This approach allowed the identification of which additive molecules contributed in modifying the material properties.

Acid-induced gelation properties of heated whey protein−pectin soluble complex (Part II): Effect of charge density of pectin

As a direct continuation of the first part of our study, here we investigate the effect of charge density of pectin on acid-induced gelation properties of heated whey protein–pectin soluble complex which was formed by heating protein and pectin together at pH 7.0 and 85 °C for 30 min. The gelation properties of complex were also compared with polymer/pectin, where whey protein and pectin were heated separately and then mixed together before acid-induced gelation. Four different types of pectin with charge density ranging from low to high were chosen. For pectin with high charge density, complex gels showed enhanced gel strength and water holding capacity compared to polymer/pectin gels. For those with low charge density pectin, polymer/pectin could not form gel network at highest pectin concentrations, whereas complex still formed gel at high pectin concentrations and showed improved water holding capacity at low pectin concentrations. Confocal micrograph showed pronounced difference in gel microstructure between complex and polymer/pectin gels. An obvious increase in the coarsening of the protein network was observed as pectin concentration increased from 0.1% to 0.5% for polymer/pectin gels. Complex gels showed much smoother network with less phase separation. At 0.25% pectin a change from a homogeneous to a coarse strand, phase separated microstructure upon decreasing charge density of pectin was observed for polymer/pectin gels, while complex gels were homogeneous even with low charged pectin. Results from scanning electron microscopy confirmed that complex gels were composed of larger protein strands and higher interconnectivity between biopolymers due to higher degree of interaction between protein and pectin.

Self-Assembling Semiconducting Polymers—Rods and Gels from Electronic Materials

In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.