Changes In Gel Properties Research Articles

Analysis of changes in gel properties during retrogradation of four kinds of sorghum starch

SummaryIn this study, four kinds of sorghum starch gels containing different amylose were taken as the research objects and stored for 28 days. The parameter changes of gel properties during the retrogradation of different varieties of sorghum starches were observed using X‐ray diffraction, Low‐field nuclear magnetic resonance, textural, rheological and anti‐enzymatic hydrolysis capacity studies to construct kinetic models for the retrogradation. The results showed that the degree of retrogradation, crystallinity and anti‐enzymatic hydrolysis capacity of sorghum starch increased with the prolongation of storage time, and the crystal forms of H5 (Hongnuo No. 5 sorghum) and L13 (Longza No.13 sorghum) starch changed from type A to B. Among the four kinds of starch, L13 starch had the highest degree of retrogradation, and H5 starch had the strongest recrystallisation ability. The hardness of L13 retrograded starch gel grew fastest with increasing storage time, while the viscoelasticity of H1 (Hongnuo No.1 sorghum) retrograded starch showed a stable trend. Low‐field nuclear magnetic resonance was used to detect that the L1 (Longmiliang No.1 sorghum) retrograded starch gel had more free water. The crystallisation rate was positively correlated with hardness, resistant starch content and crystallinity and negatively correlated with springiness, gumminess and resilience.

Ultrasound-assisted processing: Changes in gel properties, water-holding capacity, and protein aggregation of low-salt Hypophthalmichthys molitrix surimi by soy protein isolate.

The effects of ultrasound combined (25kHz, 400±20W/L, ultrasonic time of 5, 10 and 15min) with soy protein isolate processing on gelling properties of low-salt silver carp surimi, aggregation and conformation of myofibrillar protein were investigated. The results revealed that, compared with only adding soy protein isolate components, ultrasound-assisted soy protein isolate had a more obvious effect on the protein structure in low-salt surimi, leading to the decrease in α-helix and total sulfhydryl contents, and the increase in β-sheet content and protein solubility. As a result, more proteins participated in the formation of the gel network, and significant improvements in hardness, gel strength and water-holding capacity of the low-salt surimi gel were observed, while the myosin heavy chain in SDS-PAGE was weakened. The low-field NMR results showed that the initial relaxation time of T2 was apparently shorter, the free water content decreased and the bound water content increased under the action of ultrasound. Scanning electron microscope observation found that the surimi gel treated by ultrasound exhibited smaller holes, and had a more stable and denser network structure. In conclusion, the results of our work demonstrated that ultrasound combined with soy protein isolate can significantly improve the gel quality properties of low-salt silver carp.

High Molecular Weight Fucoidan Loading Into and Release from Hyaluronate‐Based Prefabricated Hydrogel and its Nanogel Particles Controlled by Variable Pitch and Differential Extensional Shear Technology of Advanced Twin Screw‐Based System

AbstractEfficient incorporation of high molecular weight drug into prefabricated hydrogel and its delivery are big challenges in its applications to drug delivery and tissue regeneration using a 3D bioprinting system. In this work, a new method of loading a model high molecular weight drug (fucoidan with 200 kDa) into prefabricated hyaluronate‐based terpolymeric gel is developed by using an advanced screw‐based extrusion printing system. This system effectively incorporates the fucoidan biomolecules into the prefabricated crosslinked gel within 60 s at significantly higher percentages without much change in gel properties. Less damage in gel network is achieved through variable pitch and differential extensional shear mechanism by optimization of bioprinting conditions. Importantly, fucoidan‐loaded nanoparticles (NPs) are developed using the advanced extrusion system at high screw rpm and with increased residence time using recirculation. The encapsulation efficiency, sustained release of fucoidan, and in vitro cell culture studies confirm the nontoxic nature of the drug‐loaded gels and nanogels at lower doses, exhibiting the biomedical application potentials of this advanced screw‐based extrusion printing system and drug‐loaded NPs formation in pharmaceuticals, 3D bioprinting, tissue engineering as well as maximal drug loading into and sustained release from prefabricated gels.

Development of reduced-salt gel of silver carp meat batter using low frequency ultrasound: Effect on color, texture, cooking loss and microstructure

Purpose: To develop reduced-salt silver carp meat gels using low frequency ultrasound.
 Methods: Silver carp meat batters were prepared with 0.5, 1 (reduced-salt) and 2 % (regular salt), and sonicated (20 KHz, 500 W) for 30 and 40 min, or unsonicated (control). Changes in gel properties were evaluated in terms of color, texture, cooking loss and microstructure using color measurement, puncture test, cooking loss and scanning electron microscopic (SEM) analysis, respectively.
 Results: Ultrasound and salt exposure led to marked effects on color, texture and cooking loss in fish meat gels (p < 0.05). Reduction in salt content increased the lightness (L*) and cooking loss; and also decreased the sample values of greenness (-a*), breaking force, rupture distance and gel strength. Scanning electron microscopy (SEM) on regular-salt level samples showed that ultrasonic exposure decreased dense aggregates and increased the number and distribution of small cavity samples. Reduced-salt samples (1 % salt) subjected to 30 min sonication had better color (lighter) than control (0 min sonication), better texture (higher gel strength) and cooking loss comparable to that of regular-salt level sample subjected to 30 min sonication, and similar to microstructures from normal salt samples without ultrasound exposure.
 Conclusion: Low frequency ultrasound is suitable for preparing reduced-salt fish meat gels under suitable ultrasonic conditions.

Myofibrillar protein conformation enhance gel properties of mixed surimi gels with Nemipterus virgatus and Hypophthalmichthys molitrix

Marine and freshwater fish surimi exhibit a synergistic effect when mixed in a suitable ratio. In this paper, we investigated changing in myofibrillar protein conformation enhance the properties of mixed surimi gels formed by thermal processing. The mixtures of Nemipterus virgatus and Hypophthalmichthys molitrix surimi were prepared (N:H mass ratios of 0:1, 1:0, 3:1, and 1:5) and analyzed during thermal processing. In particular, changes in gel properties, microstructure, and protein conformation during gel formation were studied. The obtained results show that heating increases the fracture constant of the 3:1 and 1:5 surimi mixtures from 143.64 N/m and 68.40 N/m to 442.78 N/m and 320.99 N/m, respectively, and the fracture constant of the 1:0 and 0:1 surimi from 87.07 N/m and 56.71 N/m to 443.18 N/m and 237.42 N/m, respectively. Similarly, the water holding capacities, whiteness values, β-sheet, β-turn, and disulfide bond contents of these two gels increase with increasing processing time at 40 then 90 °C. Meanwhile, nonspecific association, hydrogen bonding, and α-helix contents in the N:H = 3:1 and N:H = 1:5 samples decrease under the effect of thermal processing. Microstructural images show that the network structure of the mixed surimi gel is tighter and more compact than that of the single-component gels. Based on these results, the synergistic effect is induced by the interactions between proteins from different sources in a suitable ratio.

Myofibrillar Protein Structure and Gel Properties of Trichiurus Haumela Surimi Subjected to High Pressure or High Pressure Synergistic Heat

The changes in gel properties and myofibrillar protein structure of Trichiurus haumela surimi subjected to high pressure (300–450 MPa; 5 min) or high pressure synergistic heat (90 °C; 30 min) treatment were investigated. The results showed that high pressure below 400 MPa could improve the gel properties. The water holding capacity of the 350 MPa group increased by 27.40% compared with the control group. Moreover, the gel strength of surimi gel induced by high pressure of 300 MPa and 350 MPa increased by 38.08% and 40.00%, respectively, and continually increased by 17.86% and 21.00% after further heating. Both of high pressure and heating affected the composition of myofibrillar protein and partially degraded the actin and myosin heavy chain. High pressure reduced the contents of α-helix and β-turn, but increased β-sheet and random coil in the myofibrillar protein. Subsequent heat treatment converted the partial β-sheet into the α-helix structure. In addition, in the gels of surimi subjected to high pressure, the secondary structure of myofibrillar protein was significantly correlated with the whiteness, gel strength, and texture characteristics of the gels. Collectively, the results supported an optimum pressure of 300–350 MPa for the induction of hairtail surimi gel.

Effect of hydrocolloids on gel properties and protein secondary structure of silver carp surimi.

Hydrocolloids are the most commonly used additive in the processing of surimi products. However, the effect of hydrocolloids on surimi protein conformation has not been reported, and the level of hydrocolloids may be a key factor influencing the quality of surimi. Therefore, this study investigated the effect of curdlan, xanthan gum, κ-carrageenan, and gelatin at various levels on gel properties and protein conformation of surimi from silver carp. Addition of curdlan, κ-carrageenan, or gelatin at lower level could significantly promote gel strength, textural profiles, and water holding capacity (WHC) of the surimi gels. However, gel strength and WHC gradually decreased with increasing amount of xanthan gum added. The addition of curdlan or κ-carrageenan remarkably increased the whiteness of surimi gel, but the whiteness decreased when the concentration of κ-carrageenan reached 5 g kg-1 . Along with the increase of curdlan, κ-carrageenan, or gelatin concentration, the index of hydrophobic interaction and hydrogen bonds first increased and then decreased, whereas index of ionic bonds first decreased and then increased. According to Raman spectroscopy data, a small content of curdlan or κ-carrageenan promoted the conformational transition of surimi protein from α-helix to β-sheet, leading to the changes in gel properties of surimi gels. Scanning electron microscopy photographs showed surimi gels added with 4 g kg-1 curdlan or 2 g kg-1 κ-carrageenan had a finer and denser network structure. Curdlan or κ-carrageenan at an appropriate concentration is a potential modifier to effectively improve the quality of surimi products. © 2020 Society of Chemical Industry.

The effect of modified starches on the gel properties and protein conformation of Nemipterus virgatus surimi.

The study investigated the effect of native cassava starch (NCS), hydroxypropylated starch, acetic acid esterification starch (AAES), acetylated distarch phosphate on gel properties and protein conformation of Nemipterus virgatus surimi. Addition of 10 g kg-1 NCS or 20 g kg-1 AAES could significantly promote the gel strength and textural profiles of the surimi gels (p < .05). The water holding ability and whiteness of surimi were remarkably increased when the four types of starch were added at all concentrations (p < .05). In rheological test, the lower G' was observed in surimi samples added with starch at low temperature, suggesting starch played an inactive filler role in surimi. Along with the increase of starch additive amount, ionic bond and hydrophobic interaction first increased and then decreased, while hydrogen bond first decrease and then increased. According to Raman spectroscopy data, small content of starch promoted the heat-induced conformational transition of surimi protein from α-helix to β-sheet, leading to the change in gel properties of surimi gels. Scanning electron microscopy photographs showed surimi gels added with 20 g kg-1 starch had the finer and denser network structure. Therefore, 20 g kg-1 AAES or 10 g kg-1 NCS or 10 g kg-1 HS could be proposed to a potential modifier to effectively improve the quality of surimi products.

Effect of Reducing Agent TCEP on Translational Diffusion and Supramolecular Assembly in Aqueous Solutions of α-Casein.

The translational diffusion coefficient is highly sensitive to the size change of diffusing species and is ideally suited for the study of molecular association. Here, we used translational diffusion measurements by a pulsed-field gradient nuclear magnetic resonance (PFG NMR) technique to investigate the role of disulfide bonds in the formation of a supramolecular gel-like structure in the concentrated solution of α-casein. To reduce disulfide bonds, we added a commonly used reducing reagent tris(2-carboxyethyl)phosphine (TCEP) to α-casein solution. We found that the disruption of a disulfide bond Cys36-Cys40 in αs2-casein does not alter the translational diffusion or secondary structure of α-casein in dilute, 1 and 3% (wt %) solution. On the contrary, in concentrated, 15% (wt %) α-casein solution, in addition to the disruption of disulfide bonds, TCEP induced significant changes in gel properties. New long-lived intermolecular interactions formed, leading to the irreversible gel formation. While a few side reactions of TCEP (as well as other reducing agents, e.g., dithiothreitol) have been reported, this area is still understudied. Here, we provide new data on the side reaction of the reducing agent TCEP in concentrated protein solution, suggesting that at high protein concentrations TCEP should be used with caution.

Effect of hydroxyl-radical on the biochemical properties and structure of myofibrillar protein from Alaska pollock (Theragra chalcogramma)

The aim of the study was to investigate the effect of hydroxyl-radical on myofibrillar protein properties. Myofibrillar protein isolated from Alaska pollock muscles were incubated with oxidant agents containing different H2O2 concentrations of 0, 0.1, 1, 5, 10 and 20 mmoL/L for 1, 3 and 5 h respectively. Incubation at higher concentrations of H2O2 induced a significant decrease of protein total sulfhydryl group and an increase in protein carbonyl content in the myofibrillar fraction. Moderate H2O2 concentration (1 mmoL/L) enhanced water-holding capacity and textural properties of a gel, while lower (0.1 mmoL/L) and higher (5, 10 & 20 mmoL/L) H2O2 concentrations significantly reduced the water-holding capacity. At higher H2O2 concentration, oxidized gel revealed some resistance toward the change in gel properties. Additionally, the results from SDS-PAGE and microstructure confirmed the structural changes through aggregation and denaturation of myofibrillar components that induced changes on gelation of myofibrillar protein. The whiteness of the myofibrillar protein gel decreased significantly (p < 0.05) with increasing the concentration of H2O2. Oxidation of myofibrillar protein revealed the slight improvement of textural properties of the heat set gel at a moderate concentration of oxidant agent.

Cobalt Cross-Linked Redox-Responsive PEG Hydrogels: From Viscoelastic Liquids to Elastic Solids

We describe cobalt cross-linked redox-responsive 4-arm histidine-modified PEG (4A-PEG-His) hydrogels, which can be switched from self-healing viscoelastic liquids to form stable elastic solids through a simple oxidation step from Co2+ to Co3+. The dramatic change in gel properties is quantified in rheological measurements and is associated with the altered ligand exchange rate of the cross-linking cobalt ions. While Co2+ forms kinetically labile coordination bonds with low thermodynamic stability, Co3+ forms kinetically inert and highly stable coordination bonds. Unlike the Co2+ cross-linked hydrogels, the Co3+ cross-linked hydrogels do not dissolve in buffer and swell overtime, where they remain intact longer with increasing gel connectivity, increasing polymer concentration and decreasing temperature. Remarkably, these gels can even resist the strong chelator EDTA and withstand both low and high pH due to the low ligand exchange rates in the primary coordination sphere. Overall, the Co2+/3+ redox pair p...

Photoresponsive elastic properties of azobenzene-containing poly(ethylene-glycol)-based hydrogels.

The elastic modulus of the extracellular matrix is a dynamic property that changes during various biological processes, such as disease progression or wound healing. Most cell culture platforms, however, have traditionally exhibited static properties, making it necessary to replate cells to study the effects of different elastic moduli on cell phenotype. Recently, much progress has been made in the development of substrates with mechanisms for either increasing or decreasing stiffness in situ, but there are fewer examples of substrates that can both stiffen and soften, which may be important for simulating the effects of repeated ECM injury and resolution. In the work presented here, poly(ethylene glycol)-based hydrogels reversibly stiffen and soften with multiple light stimuli via photoisomerization of an azobenzene-containing cross-linker. Upon irradiation with cytocompatible doses of 365 nm light (10 mW/cm(2), 5 min), isomerization to the azobenzene cis configuration leads to a softening of the hydrogel up to 100-200 Pa (shear storage modulus, G'). This change in gel properties is maintained over a time scale of several hours due to the long half-life of the cis isomer. The initial modulus of the gel can be recovered upon irradiation with similar doses of visible light. With applications in mechanobiology in mind, cytocompatibility with a mechanoresponsive primary cell type is demonstrated. Porcine aortic valvular interstitial cells were encapsulated in the developed hydrogels and shown to exhibit high levels of survival, as well as a spread morphology. The developed hydrogels enable a route to the noninvasive control of substrate modulus independent of changes in the chemical composition or network connectivity, allowing for investigations of the effect of dynamic matrix stiffness on adhered cell behavior.

Changes in gel properties and water properties of Nemipterus virgatus surimi gel induced by high-pressure processing

The effects of high-pressure processing (HPP) on gel properties and water properties of Nemipterus virgatus (N. virgatus) surimi gel, the correlation among spin–spin relaxation time (T2), water holding capacity (WHC) and gel properties were studied. The results show that breaking force, breaking displacement, rupture work and WHC of surimi gels increased and then decreased significantly as the pressure increased, and reached the maximum values at 400 MPa, larger than that from 0.1 MPa and heat-set samples. It was noteworthy that cooking loss, spin–spin relaxation time (T2), solubility and myosin heavy chain (MHC) bands intensity of N. virgatus surimi gel decreased and then increased significantly as the pressure increased, lower than that from 0.1 MPa and heat-set samples, and reached the minimum values at 400 MPa. In addition, a denser network structure of N. virgatus surimi gel was achieved at 400 MPa. It indicated that high pressure of 400 MPa not only contributed to WHC improvement of N. virgatus surimi gels, decreased cooking loss and solubility, but also forming a denser, micromesh-like, more uniform, and hierarchical 3D network structure via cross-linking of MHC. This structure resulted in the increase in WHC and improvement of gel properties.

Effects of Composition of Iron-Cross-Linked Alginate Hydrogels for Cultivation of Human Dermal Fibroblasts

We investigated the suitability of ferric-ion-cross-linked alginates (Fe-alginate) with various proportions of L-guluronic acid (G) and D-mannuronic acid (M) residues as a culture substrate for human dermal fibroblasts. High-G and high-M Fe-alginate gels showed comparable efficacy in promoting initial cell adhesion and similar protein adsorption capacities, but superior cell proliferation was observed on high-G than on high-M Fe-alginate as culture time progressed. During immersion in culture medium, high-G Fe-alginate showed little change in gel properties in terms of swelling and polymer content, but the properties of high-M Fe-alginate gel were altered due to loss of ion cross-linking. However, the degree of cell proliferation on high-M Fe-alginate gel was improved after it had been stabilized by immersion in culture medium until no further changes occurred. These results suggest that the mode of cross-linkage between ferric ions and alginate differs depending on alginate composition and that the major factor giving rise to differences in cell growth on the two types of Fe-alginate films is gel stability during culture, rather than swelling of the original gel, polymer content, or protein adsorption ability. Our findings may be useful for extending the application of Fe-alginate to diverse biomedical fields.

The effects of concentration and sodium hydroxide on the rheological properties of potato starch gelatinisation

The effects of starch concentration on the gelatinisation of starch in the presence of sodium hydroxide (NaOH) were studied in dispersions containing either fixed NaOH/water ratios or fixed NaOH/starch ratios. Microscopic studies revealed that addition of NaOH to a starch dispersion induced immediate and rapid swelling of the starch granules at room temperature. On heating, granule swelling was more pronounced in the presence of NaOH. At high temperature, the granule remnants were smaller and more disperse in the presence of NaOH. Dynamic rheological measurements revealed a change in gel properties as the ratio of NaOH/water was increased. The storage modulus ( G′) showed a c 2-concentration dependence (where c is the wt% of starch as a percentage of the total sample weight), at high starch concentrations, in the absence of NaOH. As the NaOH/water ratio was increased, G′ decreased for equivalent starch concentrations, probably due to the combination of effects of the size and strength of the filler particles, the influence of ionic strength on solvent quality and charge screening, and the hydrolytic effect of NaOH on the starch chains. In the presence of NaOH and at high starch concentrations, deviations from the c 2-dependence were observed. These may be linked to incomplete chemical gelatinisation by the NaOH. In dispersions with a fixed NaOH/starch ratio of 5:95 measurements of the steady shear ( η) and complex viscosities ( η ∗) were fitted to power law equations and the fitting parameters were then plotted versus starch concentration, c. These data can then be used in the prediction of the viscosity of starch dispersions.

ＴＧａｓｅ製剤の添加によるスケトウダラとサケの予備加熱ゲルと二段加熱ゲルの品質変化

Frozen surimis of walleye pollack and chum salmon were ground with 3% NaCl and 0.3% food additive containing microbial transglutaminase (TGase). The salt-ground meats were heated at 25°C or 40°C for various periods to prepare preheated gel and subsequently heated at 90°C for 30 min to obtain two-step heated (kamaboko) gel. Quality of the gels was evaluated from the changes in gel properties (breaking strength and breaking strain) as a function of preheating time. Subunit composition of myofibrillar proteins in the gels was also analyzed by SDS-PAGE and densitometry. Results were as follows:1) Gel formation of the salt-ground meat from both frozen surimis was largely enhanced by the addition of TGase.2) The characteristic gel forming profile of each salt-ground meat induced by heating at 25, 40°C, and subsequent heating at 90°C, changed nearly the same as with TGase.3) The cross-linking reaction of myosin heavy chains markedly proceeded in the preheating gels by the addition of TGase. During the subsequent heating at 90°C, the cross-linking reaction did not proceed further.It is evident that the kamaboko gel forming nature of the salt-ground meats from walleye pollack and chum salmon frozen surimis was essentially altered by the addition of TGase. The possible non-covalent type forces between myofibrillar proteins contributing to gel formation in the presence and absence of TGase are discussed.

牛血しょう粉末を加えたスケトウダラとサケの予備加熱ゲルと二段加熱ゲルの品質

Frozen surinis of walleye pollack and chum salmon were ground with 3.0% NaC1 in the presence and absence of 0.5% food additive containing bovine plasma. Each salt-ground meat was heated at 25°C or 40°C for varied durations (preheated gel), followed by heating at 90°C for 30 min to produce two-step heated (kamaboko) gel. Quality of the gels was evaluated from the change in gel properties as a function of the preheating time. The cross-linking profile of myosin heavy chains in each gel was also investigated. The results were as follows:1) The gel properties (breaking strength and breaking strain) of the two-step heated gel were greatly enhanced by the addition of plasma powder to the salt-ground meat from both frozen surimis.2) The gel-forming profile of the salt ground meats from both surimis induced by heating at 25, 40, and by subsequent heating at 90°C, were virtually unchanged by the addition of plasma powder.It is thus evident that the characteristic gel-forming nature of the salt-ground meats from walleye pollack and chum salmon remained even if the plasma powder was added, although the gel properties of the two-step heated gel were mostly enhanced.

Role of actin filament organization in cell volume and ion channel regulation.

The actin cytoskeleton is an intracellular structure, which is involved in the onset and control of cell shape and function. In order for this relevant network to control its own and thus cell volume, specific interactions between the actin cytoskeleton and ion channel regulation controlling intracellular salt and water homeostasis may be invoked. The hypotonic shock-induced, cell volume regulatory decrease (RVD) of most eukaryotic cells is a particularly useful example, as it is initiated and regulated by concerted processes involving both adaptive changes in actin filament organization and bulk fluid extrusion triggered by saline movement and the consequent decrease in cell water. The onset of RVD is linked to the selective activation of osmotically-sensitive ion channels and other relevant ion transport mechanisms involved in the net ionic movement from the cytosol. Such regulatory processes, entailing effector changes in actin filament organization which target the plasma membrane, are largely unknown. In this report, recent studies are summarized implicating dynamic changes in gel properties of the actin cytoskeleton as the effector mechanism in the regulation of ion channel activity, and thus cell volume, in human melanoma cells. Based on the characterization of the hypotonic cell volume regulatory response of human melanoma cells devoid of a functional actin-binding protein (ABP-280, a filamin homolog) and their genetically rescued counterpart transfected with a functional ABP, a hypothesis is raised which is consistent with a regulatory "sensory" mechanism based on the ability of actin networks to respond to changes in the intracellular water-salt homeostasis, which in turn effects signals controlling membrane function, including ion channel activity.