Gel Hardness Research Articles

Gel properties of mung bean protein‑sodium caseinate hybrid yogurt: Physicochemical properties, microstructure, and intermolecular interactions

The study aimed to evaluate the gel properties of mung bean protein (MP)/sodium caseinate (NaCas) hybrid yogurt at various mixing ratios, such as rheology, texture, water holding capacity, microstructure, and formation mechanism. The gel hardness, storage modulus (G′) and water holding capacity of MP/NaCas yogurt increased and subsequently decreased as the NaCas level increased, maximum at a MP/NaCas ratio of 70:30. Meanwhile, as the MP/NaCas ratio was 70:30, the hybrid yogurt gel formed tighter and finer network structure. Moreover, the MP/NaCas hybrid yogurt slowed down the acidification rate with increasing NaCas ratio. Especially when NaCas was added at 50 %, the blend sample presented the longest fermentation time (280 min). Results showed that the optimal physicochemical characteristics of the yogurt gel were obtained when MP/NaCas ratio was mixed at 70:30. The results of the intermolecular forces indicated that hydrophobic interactions were the main factor causing yogurt gel formation.

Two-ways regulation of the emulsion gel properties of curdlan by dry ball milling treatment and their relationships with the microstructures, emulsification characteristics and gel properties of ball milled curdlan

Ball milling treatment could affect the microstructures, improve the emulsification properties of curdlan (CL) and regulate the emulsion gel properties of CL based emulsion gel in two-ways. With increasing ball milling time (1 h–8 h), the particle size first decreased and then increased, the relative crystallinity decreased, and the contact angle increased. Ball milled curdlan (BMCL)-6 h showed the best emulsifying property and stability, which was the combined effects of decreased particle size and increased hydrophobic property. Ball milling 1 h and 2 h significantly improved the hardness and chewiness of CL-based emulsion gels, while, ball milling 4 h–8 h could make the emulsion gels much softer and ice cream-like. When the emulsion gels were heated twice consecutively, the visual appearance and texture properties did not change significantly, indicating the excellent thermal stability of these emulsion gels. The BMCL based emulsion gel with adjustable gel properties and good thermal stability has a wide range of uses in the food system.

Impact of annealing and incorporation of vegetable oils on physicochemical and rheological properties of wheat starch

This study investigated the impact of annealing treatment and lipids (vegetable oils, such as palm, olive, and grapeseed oils) on the physicochemical and rheological properties of wheat starch. Annealing of wheat starch (WSANN45, WSANN55) under different temperatures (45 °C and 55 °C) and with added vegetable oil (WS-OilANN45, WS-OilANN55) were compared with untreated wheat starch (WS). Annealing at 45 °C resulted in slight changes in the physicochemical properties of starch. However, annealing at 55 °C significantly decreased the relative crystallinity, pasting viscosity, and swelling power. WS-OilANN45 showed a higher ΔH (dissociation peak) than WSANN45, indicating successful lipid incorporation, whereas WS-OilANN55 showed no significant difference from WSANN55, suggesting that lipid integration was not achieved. Rheological tests showed that WS-OilANN45 slightly reduced the shear-thinning behavior and viscoelastic properties of starch. The introduction of oils affected the swelling and pasting properties, weakened the gel network, and significantly reduced the gel hardness. This approach offers a potential method that uses food-grade oils and annealing to modify starch and alter its rheological and physical properties while retaining its native granular characteristics.

Soy protein gels based on ultrasonic treatment: Effects of Ca2+ and 11S/7S ratio on gel structures and digestive properties

This study aimed to explore the impact of varying Ca2+ concentrations and 11S/7S ratios on the gel performance of soybean protein gels (SPGs) under ultrasonication (400 W, 15 min) and to clarify the mechanisms involved. Results showed Ca2+ addition altered the structure of soybean 11S/7S protein gels. Low Ca2+ levels increased the turbidity, hardness, and water retention of the gels, whereas high levels disrupted the orderly aggregation of 11S/7S proteins, creating a rough, porous network. The effect of Ca2+ was more pronounced with a higher 11S ratio, significantly influencing turbidity, disulfide bonding, and gel hardness. Conversely, 7S-rich gels showed reduced sensitivity to Ca2+. In vitro digestion and SDS-PAGE results indicated that 7S globulin’s α, α’, and β subunits were more digestible than the A and B subunits of 11S globulin. In conclusion, ultrasound combined with Ca2+ can enhance the cross-linking degree between 11S and 7S globulin, forming a dense network structure.

Optimization of cold-induced aerated gels formed by Maillard-driven conjugates of SPI-gellan gum as an oil substitute in mayonnaise sauce

This research aimed at chracaterization of composite cold-set aerated gels composed of SPI-gellan gum Maillard conjugates. The optimized gel was eventually incorporated in mayonnaise sauce as an oil substitute. The optimum conditions were statistically determined as 1.5% SPI, 300 mM CaCl2, and 90 min heating time. All of which resulted 35% glycation degree and high molecular weight conjugates on top of SDS-PAGE injection wells. Increasing CaCl2 concentration enhanced the adsorption of conjugates at air-water interface, decreasing the density but increasing the WHC and hardness. Increasing heating time facilitated gelation which improved gel hardness. The optimized gel was microstructurally homogeneous with increased overrun (20.8%) and H-bonds. The rheological measurements showed viscoelastic gel network which was thermally stable up to 90°C, besides increasing G’, G” and η* at 85°C. Substitution of optimized gel in mayonnaise sauce improved the nutritional value and thermal stability (77.13%), but declined calorie. The substituted mayonnaise sauce was greatly accepted by panelists. Thus, the aerated gel formed at optimum conditions had great structural and mechanical characteristics and its usage as an oil analogue induced a low-calorie mayonnaise sauce with acceptable sensory properties.

Effects of moderately oxidized lard on myofibrillar protein emulsion gels: Gel-forming properties, water distribution, and digestibility

Emulsion gels were prepared by adding lard with different degrees of oxidation (0, 1, 2, 3, 4, and 5 h, 110 °C) to porcine myofibrillar proteins (MP). The findings demonstrated that changes in sulfhydryl content and carbonyl content reflected that oxidized lard induced the oxidation of MP. Compared with the control (CON), moderately oxidized lard (2 h) led to the unfolding of the protein structure, increased β-sheet content, and exposed hydrophobic groups. These modifications facilitated interactions between the protein and lard at the interface, enhancing the emulsifying properties of MPs. Furthermore, the moderate oxidation of lard (2 h) enhanced the organization of the gel structure and improved the gel performance of MPs, resulting in uniform water distribution. In contrast, the hardness and springiness of MP gel treated with excessively oxidized lard (5 h) were significantly reduced (p < 0.05). The microstructure of MP gel also exhibited irregular aggregation, resulting in a decline in protein digestibility. In addition, lard oxidation (2 h) had a positive effect on maintaining gel stability during storage.

Regulating effect of glycated rice bran protein aggregates and resultant emulsions on the gelatinization and retrogradation properties of rice starch

The effects of the rice bran protein aggregates (RBPAs), glycated rice bran protein aggregates (gRBPAs) and resultant emulsions on the gelatinization and retrogradation characteristics of rice starch (RS) were investigated. The gelatinization and retrogradation properties of RS were determined by rapid viscosity analyzer (RVA), differential scanning calorimetry (DSC), dynamic rheology, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The addition of the protein aggregates and the emulsions reduced the swelling of starch during the gelatinization process and the enthalpy change (ΔH) of RS. Meanwhile, during the long-term storage (4 °C for 21 d), the existence of the protein aggregates and the emulsions decreased the storage modulus (G′) and hardness of RS gel, thereby decelerating the retrogradation of RS. Besides, XRD analysis proved that when heated for 2 h, the relative crystallinity of the RS-gRBPAs mixture decreased by 6.08%, and the relative crystallinity of the corresponding RS-emulsions mixture reduced by 6.85%, which indicated the grafting of Dex could impede the retrogradation of RS. The inhibitory effect of adding the emulsions was more pronounced than that of adding corresponding protein aggregates. Furthermore, SEM analysis confirmed that the gel network structures of mixture were more uniform and compact compared with RS, which resulted from the protein aggregates and the emulsions inhibiting the internal combination through hydrogen bonds between starch molecules. Overall, these findings suggested that the protein aggregates and the emulsions prevented the retrogradation of RS, and could be potently used as a natural substitutes to enhance the quality and nutrition of starch-based foods.

Effect of the critical melting treatment on the short/long-term retrogradation behaviour of maize starch

The shortand long-term retrogradation properties in normal maize starch (N-S) by critical melting treatment (CMT; including TO (onset temperature) melting (OM), TP (peak temperature) melting (PM), and TC (conclusion temperature) melting (CM)) were studied. Results indicated that CMT promoted short-term (1 day) and long-term (7 days) retrogradation of N-S in the following order: PM > CM > OM. After storage for 7 days, following the PM treatment, the gel hardness, the retrogradation degree, and relative crystallinity increased to 4.67 N, 13.191%, 8.58% from 2.87 N, 9.972%, and 6.20%, respectively. PM treatment resulted in harder starch granules, promoting the rearrangement of the starch crystalline structure during cold storage. This was confirmed by the increased storage modulus, decreased iodine blue value, reduced gap in the gel network, and compact aggregate formation. Results indicated that CMT can promote the retrogradation properties of N-S.

Frabrication of carboxymethylchitin nanofibers and fish gelatin hybrid gels with robust gel performance

Compared to animal gelatin, the application of fish gelatin (FG) in the food industry is limited due to its lower gel hardness, gelation temperature, and melting temperature. To address these issues, we developed hybrid gels using carboxymethyl chitin nanofibers (CMC-NFs) with FG to enhance its gel properties. The chitin was carboxymethylated by monochloroacetic acid, increasing the negative potential from −6 mV to −35 mV. This modified chitin was then defibrillated into CMC-NFs through high-pressure homogenization to improve its water dispersibility. The addition of 0.1% CMC-NFs significantly increased the hardness of FG gels from 533 g to 989 g, which was notably higher than the ∼600 g hardness of porcine gelatin. Additionally, the gelation and melting temperatures of FG reached 17 °C and 32 °C, respectively, which are very close to the 20 °C and 35 °C of porcine gelatin. Mechanistic studies revealed that FG and CMC-NFs (0.1%) molecules formed a synergistic gel network, facilitated by hydrogen bonding and hydrophobic interactions. This interaction significantly increased the α-helix content in the secondary structure of the FG protein from 15.26% to 21.18%, thereby enhancing the FG-dominated three-dimensional network structure with CMC-NF molecules. Increasing the concentration of CMC-NFs further elevated the gel's melting temperature while reducing its hardness due to phase separation. This study not only presents a viable method for enhancing the gelling properties of modified FG but also offers a feasible solution for expanding FG's applications in the food industry.

Fucoidan-Vegetable Oil Emulsion Applied to Myosin of Silver Carp: Effect on Protein Conformation and Heat-Induced Gel Properties.

How to improve the gel properties of protein has become a research focus in the field of seafood processing. In this paper, a fucoidan (FU)-vegetable oil emulsion was prepared, and the mechanism behind the effect of emulsion on protein conformation and the heat-induced gel properties was studied. The results revealed that the FU-vegetable oil complex caused the aggregation and cross-linking of myosin, as well as increased the surface hydrophobicity and total sulfhydryl content of myosin. In addition, the addition of the compound (0.3% FU and 1% vegetable oil) significantly improved the gel strength, hardness, chewiness, and water-holding capacity of the myosin gel (p < 0.05). In particular, when the addition of camellia oil was 1%, the gel strength, hardness, chewiness, and water-holding capacity had the highest values of 612.47 g.mm, 406.80 g, 252.75 g, and 53.56%, respectively. Simultaneously, the emulsion (0.3% FU-1% vegetable oil) enhanced the hydrogen bonds and hydrophobic interaction of the myosin gels. The image of the microstructure showed that the emulsion with 0.3% FU-1% vegetable oil improved the formation of the stable three-dimensional network structure. In summary, the FU-vegetable oil complex can promote unfolding of the protein structure and improve the gel properties of myosin, thus providing a theoretical basis for the development of functional surimi products.

Effects of fermentation with Lactobacillus plantarum on rice flour: The role of granular characteristics

This study examined the effects of lactic acid bacteria fermentation on the physicochemical and functional properties of the flours from two rice varieties, Shindongjin (SF) and Hitomebore (HF), both with similar amylose content. Fermentation with Lactobacillus plantarum over 48 h resulted in significant changes. Protein content decreased substantially in both varieties, especially in SF, and amylose content increased. Swelling power and solubility also increased more in SF. The gel hardness of fermented SF increased by approximately 22 %, whereas HF showed minimal change. These differences are due to variations in granule rigidity and starch molecule leaching. SF granules maintained rigidity and a robust external network due to higher amylose leaching. In contrast, the lower initial rigidity and higher amylopectin leaching in HF hindered strong gel network formation. These findings offer insights into the structural and molecular mechanisms of rice fermentation with lactic acid bacteria.

Double-Chamber Underwater Thruster Diaphragm with Flexible Displacement Detection Function.

The purpose of this paper is to develop a self-detecting diaphragm integrated with a flexible sensor, which is utilized in an underwater thruster. Resistive strain sensors are easy to manufacture and integrate due to their advantages in reliable stretchability and ductility. Inspired by the structure of neurons, we fabricated resistive flexible sensors using silica gel as the matrix with carbon black and carbon nanotubes as additives. All fabricated sensors demonstrated positive resistance characteristics under 60% strain conditions, with the sensor containing a mass ratio of 9 wt % carbon black and carbon nanotubes exhibiting the best resistance-strain linearity. To verify the anti-interference capability of sensors with silica gel substrates of varying hardness values under changing environmental pressure, we tested the pressure sensitivity of the sensors by altering the hardness of the silica gel. The results indicate that silica gel with the highest hardness value provides the best resistance to environmental pressure interference. To detect the motion and deformation of the internal functional components of the thruster, we combined strain detection with the movement operation function of a silica gel diaphragm, resulting in a new integrated diaphragm with sensor detection capabilities. The integrated diaphragm was evaluated by using a tensile testing machine and an LCR tester. The results demonstrate that the mechanical properties of the diaphragm are stable, exhibiting reliable resistance characteristics and a sensitive response during underwater operation. This research can also be applied to the detection of motion amplitudes of other types of soft robots.

Composite starch/fermented protein emulsion gels for plant-based cheese applications

This work investigated the effect of incorporating lipids and proteins on the properties of starch-based gels relevant for plant-based cheese analogues. Gels were prepared by first fermenting protein-based emulsions to create primary gels, and subsequently using the water of these primary gels as starch hydration media to produce secondary, starch-based, pea protein-rich composite emulsion gels. Fermentation appeared to increase gel hardness compared to non-fermented protein addition. Compared to natural and crosslinked/acetylated starches, the acid-hydrolysed/acetylated starch produced firmer gels and was selected for further experimentation. Gels were macroscopically homogeneous but microscopically showed lipid coalescence at increasing lipid content (>8%), which was reduced by ultrasonicating the emulsion prior to fermentation. Dry matter content was key in determining textural and rheological properties of the gels, with starch/protein gels of 36% dry matter showing hardness and viscoelastic properties similar to those of the dairy cheese Danbo. However, the composite gels did not melt on increasing temperature up to 80 °C (delta below 20°). Proton dynamics were found to depend on gel properties and lipid addition. Overall, this work contributes towards the development of plant-based cheeses with desired characteristics by increasing their protein content and modulating their properties through fermentation and syneresis.

Effect of three polysaccharides with different charge characteristics on the properties of highland barley starch gel

Highland barley, a nutritious whole grain, faces limited market utilization due to the poor heating stability of its starch. The aim of this study was to investigate the effects of three differently charged ionic polysaccharides—guar gum (GG), xanthan gum (XG), and carboxymethyl chitosan (CMC)—on the gel properties of highland barley starch (HBS). GG and XG notably increased pasting viscosity, viscoelasticity, hardness, and strength of HBS gels. Conversely, CMC resulted in decreased gel properties. All three polysaccharides enhanced OH tensile vibration (3000–3800 cm−1), with GG and XG promoting denser honeycomb network structures and lower spin–spin relaxation time (T2), indicating improved structural integrity. In contrast, low concentrations of CMC led to disorder and loose structure. Hydrogen bonding and electrostatic interactions were the main forces by which polysaccharides influenced the properties of starch gels. This research contributes to enhancing the properties of HBS gel during heating and expanding its commercial applications. It also provides some insights to understand the interaction between different charged polysaccharides and starch.

Effect of whey protein on the formation, structure and gastrointestinal breakdown of quinoa flour-based composite gels

Whole grain flours have captured increasing attention due to their health benefits. Herein, the quinoa flour-based composite gels were fabricated by heating quinoa flour dispersions containing 0–7 w/w% whey protein isolate (WPI). The thermal properties and gel formation of the dispersions were determined, along with the large deformation and fracture properties, microstructure, and molecular reorganization of the resulting gels. Protein hydrolysis, solid loss, glucose release and microstructural changes were monitored to characterize the gastrointestinal breakdown of the gels. Results showed that gelatinization of quinoa starch occurred at 60–70 °C. Upon heating, quinoa starch was segregated into microparticles of ∼3 μm, which aggregated into the starch phase, whereas protein aggregates filled the gap of the starch gel network. A bicontinuous structure was formed with increasing WPI concentration to 7 w/w%. Meanwhile, the storage modulus, gel hardness and fracture stress of the gels increased by 5–8 times. The addition of WPI inhibited gel disintegration during in vitro digestion. However, intestinal glucose release was not delayed because of the phase-separated structure of the gels. With increasing WPI concentration, larger protein aggregates survived after 5 min of intestinal digestion, demonstrating that the enhanced protein network was the main contributor slowing down gel disintegration during in vitro digestion. This work would promote the development of quinoa flour-based products with controlled digestion.

Lactic acid bacteria fermentation-induced egg white protein structure deformation influencing gelling properties, with membrane concentration as a strategy to improve texture.

Egg white (EW), a rich protein source, holds promise for creating a high-protein, low-fat gel product. However, browning issues during heating and sterilization have hindered its wider application. In this study, lactic acid bacteria fermentation was employed to eliminate reducing sugar in EW, and its impact on the molecular structure and gelling properties was explored. The results revealed that fermentation would trigger protein structural unfolding and aggregation, evident from higher fluorescence intensity and enlarged protein particle diameters, resulting in the decrease in gelling hardness. In comparison, Streptococcus thermophilus-fermented EW (under 6×108CFU/mL incubation rate, fermented for 6h) exhibited the highest gel hardness, ascribed to the relatively weaker structure transformation, with high water holding capacity and stronger intermolecular hydrophobic interaction. To further enhance the gelling properties of fermented EW, membrane concentration treatment was applied, exhibiting superior characteristics in appearance, aroma, and taste. In summary, lactic acid bacteria fermentation and concentration are feasible solutions to improve appearance and texture of EW gels simultaneously. The research findings offer eco-friendly and practical strategies for enhancing the quality of EW gels, providing valuable theoretical insights for the development of innovative, texture-rich, and healthy nutritional foods.

Fabrication and characterization of novel curcumin-loaded thermoreversible high amylose maize starch emulsion gel

This study developed a novel thermoreversible emulsion gel system based on high amylose maize starch (HAMS) and investigated the impact of the oil-to-water ratio on its physicochemical properties and encapsulation performance (using curcumin as model guest molecule). Electron microscopy showed a tightly porous network structure of the HAMS-based emulsion gels. Thermal results revealed a sol-gel transition occurring in the range of 59.41 to 67.64 °C for the prepared emulsion gels. Rheological analysis suggested that all samples displayed shear-thinning behavior and HAMS-based emulsion gels exhibited typical gel-like behavior with the gel strength bolstered by higher aqueous phases. Particle size analysis showed that droplet size of emulsion gel decreased from 245 to 184 nm with increased starch aqueous phase content. Texture profile analysis indicated enhanced strength, hardness, and chewiness of the emulsion gel with increased aqueous phases. Curcumin encapsulation efficiency in the HAMS-based emulsion gel also improved with higher aqueous phase content, reaching up to 93.82 %, which attributed to the smaller droplets caused increased interfacial area. The novel HAMS-based emulsion gel system showed considerable encapsulation capacity and desirable mechanical properties. It provided valuable insights into the application of starch-based emulsion gels in food and medical area.

The Impact of Adding a Cationic Metal Salt and Curcumin to Monoammonium Glycyrrhizic Acid on Its Solubilizing Capacity and Gelation.

Monoammonium glycyrrhizic acid (MAG), a glycyrrhizic acid monoammonium salt, is a naturally derived low-molecular-weight gelling agent with surface-active properties. It has the capacity to individually facilitate the preparation of gel-solubilized drugs. As MAG is an anionic surfactant with carboxyl groups, the addition of counterions may affect micelle formation and gelation. In this study, the solubilization and gelling properties of MAG were investigated following the addition of metal salts (NaCl and KCl). The addition of metal salts resulted in a decrease in the critical micelle concentration and an increase in gel hardness. Supersaturation of curcumin (CUR) was maintained by the addition of metal salts because of increased micelle number and viscosity. When the gel hardness was compared between formulations with and without CUR, a significant reduction in hardness was observed with the solubilization of CUR. The addition of KCl prevented the decrease in the hardness of gels containing CUR compared to the addition of NaCl. Put together, the addition of metal salts had a noteworthy impact on micelle and gel formation of MAG. In particular, the addition of KCl was more effective in the preparation of gel-solubilized CUR.

Impact of ultrasonic and heat treatments on the physicochemical properties and rennet-induced coagulation characteristics of milk from various species

This study investigates the effects of heat and ultrasonic treatments on the physicochemical parameters and rennet-induced coagulation properties of milk from a variety of species, including cow, goat, buffalo, and donkey. Milk samples were subjected to heat treatments at different temperatures (65 °C, 80 °C, 90 °C, 100 °C) and ultrasonic treatment at varying power levels (200 W, 400 W, 600 W, 800 W, 1000 W). The results revealed that changes in turbidity, particle size, zeta potential, secondary structure, and surface hydrophobicity were altered by both ultrasonic and heat treatments, as well as the kind of milk. Ultrasonic treatment of cow milk decreased α-helix content while increasing β-turn content. Under similar ultrasonic treatment, goat milk showed a considerable increase in β-sheet content, whereas β-turn and random coil contents decreased compared to control samples. Notably, the water-holding capacity of gels formed from all four types of milk increased significantly with the intensity of ultrasonic and heat treatments. The hardness of buffalo milk gels increased significantly after ultrasonic and thermal treatments, ranging from 63 °C for 30 min to 90 °C for 15 min, but the hardness of cow and goat milk gels increased in varying degrees compared to their control samples. Furthermore, gels from cow and goat milk had higher storage modulus (G’) and loss modulus (G’’) than those from buffalo and donkey milk, and changes in G’ and G’’ from the examined milk were altered by ultrasonic and heat treatments. These findings offer important insights into refining milk processing procedures to improve dairy product quality and usefulness.

Construction of mixed gels of yolk granules and salted ovalbumin driven by pH: phase behavior and calcium bioaccessibility

Mixed gels of egg yolk granules (EYGs) and salted ovalbumin (SO) with different pH values were constructed to design gels of great quality and nutritional properties. However, the formation and dietary properties of mixed gels may be affected by the phase behavior of the mixed protein solution. In this study, the pH was adjusted from 3.0 to 8.0 to tune phase behavior of mixed protein solution before heating. The results demonstrated the presence of a collapsed gel and a dense phase network at pH 3.0 caused by phase separation. As the pH increased and phase separation disappeared, the EYGs-SO gel network showed a filling network structure and then changed to a loose interpenetrating network gel structure with a decreased fractal dimension (from 2.94% to 2.89%). The interpenetrating network improved gel hardness and water-holding capacity. During gelation, the phase separation reduced the gelation transition temperature. The main forces that support EYGs-SO gel were hydrogen and disulfide bonds. Moreover, EYGs-SO showed greater calcium bioaccessibility (7.85%–8.08%) at pH 3.0, 4.0, and 5.0. In summary, the phase behavior in mixed solution modulates the gelation of mixed gels. The construction of mixed gels also provides ideas and strategies for the value-added utilization of salted egg whites.