Properties Of Heat-induced Gels Research Articles

Enhanced characterization and utilization of cowpea protein isolate: rheological and textural properties of heat-induced gels for plant-based egg omelet formulation

This study aimed to evaluate the potential of cowpea isolate (CPI) as an effective plant-based egg substitute by comparing its composition and physicochemical properties with those of commercial isolates, including mung bean, soy, and pea proteins. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis identified a distinctive vicilin-like globulin in CPI that is critical for the unique functional properties of CPI. CPI has a smaller particle size, resulting in superior gelation capacity and water retention, which are essential for egg substitute applications. Thermal analysis revealed the high stability of CPI, which is advantageous for food processing. Notably, the unique heat-induced gelation behavior of CPI, characterized by a smooth transition from solid- to liquid-like states, provided a strength not observed in its commercial counterparts. Microstructural analysis showed that the CPI gel closely resembled the egg gel, underscoring the potential of CPI to mimic the texture of eggs, particularly in omelets.

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.

Relationship between soybean protein composition and breaking load of heat-induced gel prepared from acid-precipitated soybean flour

To understand the effective soy protein composition for realizing appropriate meat substitute, we evaluated the contribution of four protein fractions separated from soybeans, two types of globulins and two types of lipophilic proteins, to textural properties of heat-induced gels prepared from an acid-precipitate of soybean flour (AP-SF). When we added these fractions sduring the preparation of AP-SF gels, which increased the protein content by 10%, the gel with 7S globulin displayed the highest breaking load (417.7 gf). With respect to combinatorial effects, the AP-SF gel that added with 5% 7S and 5% 11S globulin reached an even higher value (460.2 gf) than the value described above (417.7gf).To further support the contribution of fractions, we investigated the correlation between the content of these four protein fractions in soybean flour from different cultivars and the breaking load of the heat-induced gels. The breaking load shows a stronger correlation with the total amount of 7S and 11S (r = 0.86) than with 7S alone (r = 0.77), 11S alone (r = 0.70), or the total amount of acid-precipitated proteins (r = 0.80). Thorough this research, we obtained new findings suggesting a synergistic effect between both globulins.

Protein interactions and rheological properties of heat-induced gels containing soy and water-soluble mealworm (Tenebrio molitor larvae) protein mixtures

This study investigates the protein interactions, rheological properties, and gel characteristics of complex protein gels prepared using varying ratios of soy protein isolate (SPI) and water-soluble mealworm protein (WS-MP). After heat treatment, the particle size increased for all ratios, and the absolute zeta potential exhibited a decreasing trend with higher WS-MP ratios. A comparison of SDS-PAGE profiles before and after heating indicated that disappeared bands may be associated with gelation. Furthermore, as the WS-MP ratio increased, the dominant molecular forces within the gels shifted from hydrophobic interactions and disulfide (SS) bonds to ionic and SS bonds. The SS content decreased as the WS-MP ratio increased. The surface hydrophobicity displayed an initial decrease followed by increased gels. Rheological analysis revealed that gel elasticity decreased as the WS-MP ratio increased, although no significant difference in gel elasticity was observed when the WS-MP ratio exceeded 50%. Heat-induced gels with different SPI:WS-MP ratios exhibited different color and turbidity characteristics. Heat-induced gels comprising the SPI:WS-MP mixture exhibited lower hardness and gumminess than single SPI and WS-MP heat-induced gels. Furthermore, the water holding capacity and the uniformity of gel microstructure exhibited a decreasing trend with an increasing WS-MP ratio. In conclusion, the results suggest that WS-MP can enhance the texture of SPI gels, with the optimal ratio depending on the desired gel properties.

Effects of konjac glucomannan as a freeze-denaturation inhibitor or binder on the physiochemical properties of heat-induced gel of freeze-dried duck blood.

During freeze-drying, the degradation or eutectic melting of duck blood proteins can reduce the quality of duck blood gels. However, the interaction between proteins and polysaccharides during drying can improve protein-based gel quality. Therefore, here, we investigated the physicochemical properties of heat-induced gels of freeze-dried duck blood (FDB) and FDB with different proportions of the polysaccharide konjac glucomannan (KG), which serves as a freeze-denaturation inhibitor agent (FDA) or binder (BG). The pH and water-holding capacity (WHC) of FDB + KG gels were higher than those of FDB gel without KG (control). Especially, the WHC increased from 11.00% for control to 55.65% for FDB gel with 1% KG as a BG. Consequently, cooking loss and texture parameters of FDB + KG gels decreased. The hardness of control was 2.14kg, which significantly reduced to 0.12-0.87kg with KG addition. The highest carbonyl content was observed in control gel, and the thiobarbituric acid reactive substance content was reduced by the addition of 1% KG as an FDA (T1) or 0.8% KG as an FDA with 0.2% KG as a BG (T2) (p<0.05). These changes might be induced by the alteration of tertiary structure and thermodynamic stability of gels. In conclusion, 1% KG can be used as an FDA to improve the quality and physicochemical properties of heat-induced gels of FDB. Optimized FDB gels with KG can be used as an innovative food ingredient to fortify nutrition and develop special dietary purposes.

Heat-induced gels from pea protein soluble colloidal aggregates: Effect of calcium addition or pH adjustment on gelation behavior and rheological properties

Heat-induced protein gels are appreciated due to their texture in a variety of food products. To support the shift to more sustainable protein consumption more knowledge is needed about plant protein gelation behavior and rheological properties of gels. In this study, the effect of calcium concentration (10 mM–100 mM) and pH (5.9–6.8) on heat-induced gelation behavior of 10 w/w% pea protein water-soluble extract separated from a commercial pea protein isolate (WSE-PPI) were for the first time investigated and compared. The rheological results show Gʹ values of around 3000 Pa for gels containing 20 mM calcium, and then a decrease in Gʹ by a factor ∼1.3 when the calcium concentration increased to 100 mM, whereas a continuous increase in gel strength was observed with the pH decrease of WSE-PPI dispersions. By comparison of calcium-addition and pH-adjusted heat-induced gels at the same pH, it was found that at low calcium concentrations (≤20 mM), the calcium-assisted gels exhibited higher gel strength. Contrariwise, at high calcium concentrations (≥50 mM), the pH-adjusted gels have higher gel stiffness and larger deformability before rupture. CLSM results verified this finding and show that the gel structure of pH-adjusted gels are more homogenous, containing significantly more compact structure. Overall, our findings show a systematic link between microstructure and rheological properties of heat-induced gels, which can be controlled by the calcium addition and pH adjustment. These results provide valuable information for the modulation, design, and customization of plant derived protein gels for specific food applications.

Quantitative proteomics provides insights into the mechanism of the differences in heat-induced gel properties for egg white proteins with different interior quality during ageing in laying hens.

The purpose of this study was to investigate the mechanism for the differences in heat-induced gel properties of egg white proteins with different interior quality during ageing in laying hens. Quantitative proteomic analysis revealed that the abundance of ovotransferrin, avidin, mucin 5B, and clusterin increased with decreasing Haugh units (HU), leading to the transition from disorder to order in the secondary and tertiary structure of egg white proteins, with the burial of hydrophobic groups and a reduction in the negative charge on the protein surface, rendering the egg white protein solution aggregated. These changes would accelerate the rate of aggregation of egg white proteins during heating, resulting in the loss of orientation of the molecular chains, forming coarse and porous gel structures and poor gel properties. This research provides a new idea for improving the gelling properties of egg whites from lower interior quality during ageing in laying hens.

Effects of carboxymethyl chitosan on the gelling properties, microstructure, and molecular forces of Pleurotus eryngii protein gels

Protein-polysaccharide interactions play a crucial role in development of plant-based food products. This study aimed to investigate the effects of different carboxymethyl chitosan (CMCS) concentrations (0–5.0%) on the gelation, structural properties, molecular interactions, and microstructure of the Pleurotus eryngii protein (PEP) gels. The results showed that the addition of CMCS could improve the rheological, textural properties and water holding capacity of the PEP/CMCS composite gels. Fluorescence spectra, fourier transform infrared spectrum and chemical interaction forces analysis suggested that the formation of the CMCS/PEP complex occurred by static quenching mechanism. The addition of CMCS changed the secondary structure and molecular conformation of the protein, also significantly enhanced the hydrophobic interaction and disulfide bonds of PEP molecules, thus increased the gel properties of PEP. Scanning electron microscopy revealed a denser and uniform network structure with small pores in the CMCS/PEP composite gels. Overall, these results provided an important basis for CMCS to improve the heat-induced gel properties of PEP, and also provided information on the potential use of composite gel as meat analogs in the food processing industry.

Synergistic improvement of quinoa protein heat-induced gel properties treated by high-intensity ultrasound combined with transglutaminase.

Quinoa protein is enriched with a wide range of amino acids, including all nine essential amino acids necessary for the human body, and in appropriate proportions. However, as the main ingredient of gluten-free food, it is difficult for quinoa to form a certain network structure for lack of gluten protein. The aim of this work was to enhance the gel properties of quinoa protein. Therefore, the texture characteristics of quinoa protein treated with different ultrasound intensities coupled with transglutaminase (TGase) were investigated. The gel strength of quinoa protein gel increased markedly by 94.12% with 600 W ultrasonic treatment, and the water holding capacity increased from 56.6% to 68.33%. The gel solubility was reduced and free amino content increased the apparent viscosity and the consistency index. Changes in the free sulfhydryl group and hydrophobicity indicated that ultrasound stretched protein molecules and exposed active sites. The enhanced intrinsic fluorescence intensity at 600 W demonstrated that ultrasonic treatment affected the conformation of quinoa protein. New bands emerged in sodium dodecylsulfate-polyacrylamide gel electrophoresis indicating that high-molecular-weight polymers were generated through TGase-mediated isopeptide bonds. Furthermore, scanning electron microscopy showed that the gel network structure of TGase-catalyzed quinoa protein was more uniform and denser, thereby improving the gel quality of quinoa protein. The results suggested that high-intensity ultrasound combined with TGase would be an effective way to develop higher-quality quinoa protein gel. © 2023 Society of Chemical Industry.

Soluble-protein-aggregate-assisted improvements in heat-induced gel properties: Effect of genipin-mediated crosslinks on egg white protein

Genipin, a covalent crosslinker, has attracted significant attention from the food industry. Herein, the color, heat-induced gelling properties, and soluble aggregate character of the genipin-treated egg white were investigated to clarify the impact of soluble protein aggregates on the gel properties of egg white protein.After genipin pretreatment, the egg white protein turned dark blue and retained this color after heat-induced gelling. The genipin-pretreated egg white protein gel exhibited up to 2.9-fold and 13% higher breaking strength and strain, respectively, compared to non-treated egg white gel. The gel-breaking strength and strain correlated well with the color, before and after gelling. Gel electrophoresis, size exclusion, and anion exchange high-performance liquid chromatography revealed that a soluble protein aggregate with a negatively charged surface formed during pretreatment. The genipin-treated egg white protein formed a finely structured gel with high breaking strength and strain at all tested NaCl concentrations, indicating that the enhanced negative charge of the surface did not contribute to improving the gel properties.The soluble protein aggregates formed via covalent crosslinking are important for improving gel properties. The proposed method is a novel environmentally friendly method for enhancing the gel properties of egg white protein.

Structural and gelling properties of whey proteins influenced by various acids: Experimental and computational approaches

Five different acids, i.e., hydrochloric acid (HCl), acetic acid, lactic acid, γ-aminobutyric acid (GABA) and taurine were applied to investigated their effects on heat-induced gelation properties of whey protein isolate (WPI) at pH = 5.5. All WPI gels were found to have self-similar structures with the fractal dimension, df = 2.40. Those denatured WPI formed strong physical gels that were susceptible to shear and strain. Of all the acids, HCl, GABA and taurine significantly strengthened WPI gels. Moreover, denser packing of protein aggregates was observed from the gels with GABA and taurine. Besides experimental approaches, molecular dynamics (MD) simulations were also applied to investigate the effects of various acids on denaturation of β-lactoglobulin (β-LG). GABA and taurine were found to protect β-LG from denaturation and delayed the molecular heat-induced unfolding. Moreover, presence of HCl, GABA and taurine conserved the rigidity of unfolded β-LG and localized the residue –SH121, which was believed to result in promoted reaction-limited clustering aggregations (RLCA) of β-LG molecules and strengthened WPI gels. Further studies suggested that there was no strong binding or aggregation between cations (Na+) or anions/zwitterions and β-LG molecule. Therefore, the effects from various acids (anions/zwitterions) on β-LG and WPI were supposed to result from long-distanced electrostatic interactions and/or their effects on the protein hydration shells.

Rheological and textural properties of heat-induced gels from pulse protein isolates: Lentil, mungbean and yellow pea

The molecular structure and conformation of the plant-based proteins dominate their gelation behaviour. These aspects have been mostly overlooked for underutilised pulse proteins such as lentils and mungbean that differ structurally with soy and pea proteins. Rheological and textural properties of heat-induced gels of lentils (LPIs) (green, red and black lentils), mungbean (MBPI) and yellow pea (YPPI) were compared with commercial soy (CSPI) and pea (CPPI) protein isolates. On investigation of the dynamic rheological parameters, the critical protein concentration (CPC) of MBPI was the lowest (14% w/v) followed by LPIs (18% w/v) and YPPI (22% w/v). Also, vicilin-rich MBPI showed a lower gelation temperature (Tgel 77 °C) and developed stronger gels compared to LPIs and YPPI. On the other hand, commercial isolates with larger particle size, water holding capacity and denatured state showed lower CPC (CPPI, 14% w/v) than their folded and more soluble counterparts (YPPI 22% w/v). Hence, the study of thermo-rheological properties of pulse proteins with distinct molecular and conformation characteristics has yielded a structure-gelation paradigm. These findings support the development of plant protein-gelled products not limited to meat and dairy analogues.

Evaluation of ionic calcium and protein concentration on heat- and cold-induced gelation of whey protein isolate gels as a potential food formulation for 3D food printing

3D food printing (3DFP) is an innovative food process, but developing foods with ideal printability can prove challenging. Whey protein isolate (WPI) gels can be difficult to print due to their rigidity. This study evaluated the cold- and heat-induced gelation properties of WPI for use in 3DFP. Initially, the effect of WPI concentration ([WPI]) (8–12% (w/w)) and ionic calcium concentration ([Ca2+]) (0–8 mM) was evaluated on the heat-induced gelation capability and thermal reversibility. Treatments were categorised into three groups: thermo-irreversible, thermo-reversible, and non-gelling. Non-gelling treatments were used for cold-induced gelation by mixing the denatured WPI solution with 150 mM Ca2+ solution. Thermo-reversibility and cold-induced gelation properties were assessed using oscillatory rheometry. Finally, thermo-irreversible gels (TIRG) were characterised using extrudability and texture profile analysis. The thermo-reversible gels had an unsuitable range of G' (5–60 Pa) and δ (40–60°) for obtaining a self-standing object. Cold gelation using [WPI] = 10%, G' > 500 Pa and δ < 10°, may be suitable for 3DFP but requires an adapted extrusion-based 3D printer, i.e., co-extrusion, cooling or support bath. The extrusion force of TIRG decreased during heating and was mainly affected by [WPI]. Upon re-cooling, the force recovered (>85%) with the addition of [Ca2+] > 4 mM. TIRG using the following treatments [WPI]-[Ca2+] = 12% - 2 mM, 11% - 4 mM, and 10% - 6 mM demonstrated good printability. Principal component analysis showed TIRG with low hardness, resilience, and extrusion force loss during heating are potentially suitable for 3DFP.

Microstructural and rheological properties of heat-induced gels from mung bean protein aggregates

Microstructural and rheological properties of heat-induced gels from mung bean protein aggregates

L-histidine inhibits the heat-induced gelation of actomyosin in a low ionic strength solution.

The heat-induced gelation of actomyosin plays a key role in meat processing. Our previous study showed that L-histidine could affect the characteristics of a heat-induced gel of myosin on a low ionic strength. To apply the specific effect of L-histidine to meat processing, the heat-induced gel properties of actomyosin in the presence of L-histidine were investigated. Actomyosin in a low ionic strength solution containing L-histidine did not form a gel upon heating. The dynamic rheological properties of actomyosin in low ionic strength solutions were distinct depending on the presence or absence of L-histidine. Electron microscopy showed that, heated at 50°C, actomyosin in a low ionic strength solution containing L-histidine remained a filamentous structure. The surface hydrophobicity of actomyosin was stable up to 50°C in a low ionic strength solution containing L-histidine. In conclusion, L-histidine might suppress the aggregation of actomyosin and inhibit heat-induced gelation in a low ionic strength solution.

Understanding the differences in heat-induced gel properties of twelve legume proteins: A comparative study

This study aimed to investigate the rheological and textural properties of heat-induced gels from twelve legume protein isolates at pH 3.0 and 7.0, including black kidney bean (BKPI), speckled kidney bean (SKPI), panda bean (PDPI), cowpea (CPPI), mung bean (MPI), adzuki bean (API), rice bean (RPI), black soybean (BPI), soybean (SPI), chickpea (CPI), broad bean (BRPI) and pea (PPI). SDS-PAGE revealed that 7S globulin was prominent protein in BKPI, SKPI, PDPI, CPPI, MPI, API and RPI, the main protein fraction of CPI was 11S globulin, and BPI, SPI, BRPI and PPI contained both 7S and 11S globulins as major components. Based on the gel’s Power Law constant (K’) and hardness, twelve legume proteins were divided into three categories with high, medium and low gel strength. BKPI, SKPI and PDPI with Phaseolin being the major protein fraction showed high gel strength regardless of pH. Electrostatic interactions, hydrophobic interactions and hydrogen bonds were the most important intermolecular forces in the formation of legume protein gel networks, of which gel strength at pH 3.0 and pH 7.0 was significantly affected by electrostatic interactions and hydrogen bonds, respectively. Moreover, gel strength was also remarkably negatively influenced by the non-network proteins. SEM observation indicated that the microstructure of gels at pH 7.0 was denser and more homogeneous than that at pH 3.0, leading to better water holding capacity. These findings would be of great importance for understanding the differences in legume protein gels, and also laid the scientific support for expanding applications of legume proteins in gel-based foods.

Improvement of the gel properties and flavor adsorption capacity of fish myosin upon yeast β-glucan incorporation

The potential effects of yeast β-glucan (YG) on heat-induced gel properties, microstructure and flavor adsorption capacity of fish myosin at different NaCl concentrations were investigated in this study. The incorporation of YG significantly improved the texture properties, gel strength, water holding capacity (WHC), storage modulus and loss modulus of myosin gels, especially at a high salt level, whereas the whiteness declined. Furthermore, myosin gels containing YG displayed a more compact and ordered three-dimensional network structure, accompanied by the increasing immobilization of water in gels. The binding abilities of gels to selected flavor compounds at high salt content were inferior to those at the low salt content. Regardless of the salt level, YG addition boosted the flavor binding capacity of gels, which might be attributed to the unfolding of the protein conformation by exposing more flavor-binding sites, as well as the porous sponge structure of YG with unique adsorption capacity.

Impact of Phytase Treatment and Calcium Addition on Gelation of a Protein-Enriched Rapeseed Fraction

Rapeseed press cake was upcycled as a protein-enriched ingredient through dry fractionation. The protein-enriched fraction contained higher amounts of phytic acid compared to press cake, and phytase treatment was applied to decrease the phytic acid content from 6.8 to 0.5%. The effect of phytase treatment leading to the release of cations was also mimicked by extrinsic calcium addition. Both phytase treatment and calcium addition significantly improved the heat-induced gel properties but had a minor effect on protein solubility and dispersion stability at pH 8. Water and protein holding capacities of the gels were the highest for the phytase-treated sample (91 and 97%, respectively), followed by the sample with added calcium (86 and 94%, respectively) and control sample (60 and 86%, respectively). Gel firmness followed the same pattern. Scanning electron microscopy images revealed an interconnected structured network in the phytase-treated gel, while in the control gel, a more rigid and open structure was observed. The improved gelation properties resulting from the phytase treatment suggest that the protein and soluble dietary fibre-enriched rapeseed press cake ingredient serve as a promising raw material for gelled food systems. The positive effect of calcium addition on gel properties proposes that part of the improvement observed after phytase treatment may be caused by cations released from phytate.

Relationship between Molecular Structure and Heat-Induced Gel Properties of Duck Myofibrillar Proteins Affected by the Addition of Pea Protein Isolate.

This paper investigates the relationship between the molecular structure and thermally induced gel properties of duck myofibrillar protein isolate (DMPI) as influenced by the addition of pea protein isolate (PPI). The results showed that b* value of the gels increased; however, a* value decreased with the increase of PPI content (p < 0.05). The whiteness of the gels decreased significantly with the addition of pea protein compared with 0% vs. 0.5% addition. Nuclear magnetic resonance tests showed the area of immobilized water also increased with increasing PPI addition (0–2%), thus consistent with the increased water-holding capacity (p < 0.05). The penetration force of the gels increased with increasing PPI addition (p < 0.05), while the storage modulus and loss modulus of the gels were also found to increase, accompanied by the transformation of the α-helix structure into β-sheet, resulting in better dynamics of gel formation. These results indicated the gel-forming ability of DMPI, including water retention and textural properties, improves with increasing PPI addition. Principal component analysis verified these interrelationships. Thus, pea protein could improve the properties of duck myofibrillar protein gels to some extent and improve their microstructure, potentially facilitating the transition from a weak to a non-aggregated, rigid structure.

Impact of incorporations of various polysaccharides on rheological and microstructural characteristics of heat-induced quinoa protein isolate gels

This study aimed to investigate the properties of heat-induced gels (85 °C for 30 min) of quinoa protein isolate (QPI) in the presence and absence of various polysaccharides including guar gum (GG), locust bean gum (LBG), and xanthan gum (XG) at pH 7. For this purpose, samples with three gum concentrations (0.05, 0.1, and 0.2 wt%) at a fixed QPI concentration (10 wt%) and a fixed ionic strength (50 mM NaCl) were studied in terms of their gelation behaviour, small and large deformation rheological properties, water holding capabilities, and microstructural characteristics. Rheological measurements revealed that all polysaccharides incorporation could improve gel strength (complex modulus, G*) and breaking stress, accelerate gel formations, and more stiffer gels were obtained at greater polysaccharide concentrations. The XG exhibited the most gel strengthening effect followed by LBG and GG. Incorporation of 0.2 wt% XG led to a 15 folds increase in G* compared to the control. Confocal laser scanning microscopy observation revealed that the polysaccharides also altered gel microstructures, with the gels containing XG showing the most compact gel structures. The findings of this study may provide useful information for the fabrication of novel QPI based food gel products with improved texture.