Heat-induced Gel Formation Research Articles

Heat-induced gel formation by whey protein isolate-deacetylated konjac glucomannan at varying pH conditions

This study explored the formation of composite gels via pH-modulated whey protein isolate (WPI) and deacetylated konjac glucomannan (KGM) solutions. The physicochemical properties, gelation characteristics, and microstructure of WPI-KGM gels were evaluated at varied pH levels (2−10). Findings revealed that WPI and deacetylated KGM failed to generate a stable gel at pH extremes (2 or 10). However, under optimal pH conditions (4 or 8), the WPI-KGM system yielded gels exhibiting superior water-holding capacity and hardness after heat treatment, with the composite gel at pH 4 demonstrating enhanced whiteness compared to that at pH 8. Textural and rheological assessments suggested that moderate pH levels favor the formation of well-structured gels. Scanning electron microscopy showed denser structures at pH 4 and 8, contrasting with disordered, coarse gel networks at pH 2 and 6. At pH 4, the WPI-KGM gel structure was primarily maintained by electrostatic and hydrophobic interactions, whereas at pH 8, disulfide bonds became pivotal. Overall, our findings underlined the importance of appropriate pH conditions in facilitating composite gel formation, offering practical insights for heat-induced gel material development in the food industry.

Ovomucin may be the key protein involved in the early formation of egg-white thermal gel

Clarification of the mechanism of heat-induced gel formation by proteins under natural food systems could provide important references for the regulation of food texture. In the present study, the proteins involved in the early stage (heating at 72 °C for 8 min) of egg-white thermal gel (EWG) formation were studied quantitatively through comparative proteomic analysis. We discovered that the abundance of ovalbumin and ovomucoid increased significantly (p < 0.01), whereas that of ovotransferrin, lysozyme, ovomucin (mucin 5B and mucin 6) decreased significantly (p < 0.01), in the supernatant of EWG. If the initial interaction of egg white proteins was altered by ultrasonic pretreatment, the abundance of ovomucin and lysozyme in the supernatant of EWG increased, and was accompanied by the change from a solid gel to a fluid gel. Based on these results, we hypothesize that ovomucin has a key role in the formation and regulation of EWG properties.

Heat-induced gel formation by whey protein isolate-Lycium barbarum polysaccharides at varying pHs

Effects of different levels (0, 0.1, 0.5, and 1% w/v) of Lycium barbarum polysaccharides (LBP) were investigated on the gel properties of heat-induced whey protein gels forming at varying pHs (3.0, 5.2 and 7.0). The textural, rheological, hydration properties and microstructure of gels were evaluated. Results exhibited that the composite gel containing 0.1% (w/v) LBP showed the greatest functional valorization, whereas higher concentrations of LBP (1% w/v) yielded hydrogels with higher porosity, which was confirmed by scanning electron microscopy. Moreover, whey protein formed white particulate gels and transparent fibrillar gels at pH values near to and far from the isoelectric point, respectively. As for hydration properties, no difference in water holding capacity and swelling property was observed at all pHs. This study simulated the conditions used in practical production, aiming to provide a theoretical basis for the application of LBP on composite gels and develop tunable gel-type food to satisfy different consumer preferences.

Structural changes induced by direct current magnetic field improve water holding capacity of pork myofibrillar protein gels

The study was to investigate the role of direct current magnetic field (DC-MF) for water-holding capacity (WHC) of myofibrillar protein gels and to understand potential mechanisms. Samples were subjected to DC-MF with different intensities (3.5, 3.8, 9.5 and 10.4 mT), and DC-MF treatment significantly improved WHC compared with control (46.09%), reaching the maximum value of 50.36% at 3.8 mT. The main reason for the increase in WHC might be that DC-MF modified the protein structure via unfolding, re-crosslinking and aggregation of proteins, which was supported by the increased intensity of tyrosine, aliphatic and tryptophan residues, and reduced reactive sulfhydryl (2.97 to 1.94). And the re-crosslinking between molecules was maintained mainly through hydrophobic interactions and disulfide bonds. Besides, DC-MF treatment helped to generate a relatively loose and uniform microstructure to trap more water as shown by electron microscope image, which was consistent with the highest WHC at 3.8 mT.

Heat-induced gel formation of a protein-rich extract from the microalga Chlorella sorokiniana

Abstract Microalgae proteins are an underutilized biomass source for foods with unknown technofunctionalities. Heat-induced gel formation was used in this study to investigate the gelation properties of a protein-rich extract from the microalga Chlorella sorokiniana. Gel formation was achieved at a minimum protein concentration of 9.9 g/100 mL and a temperature of 61 °C was necessary to produce a stable gel network. Small-amplitude oscillatory shear measurements revealed that a weak gel was formed with tan δ > 0.1, which was also evident during backward extrusion measurements. The elasticity of the gels increased when the final Tset was increased and a maximum gel elasticity was obtained at Tset = 80 °C and a heating rate of 1 °C min−1. Increasing the heating rate to 5 and 15 °C min−1 negatively affected the gel strength. Additionally, increasing the ionic-strength and increasing or decreasing the pH negatively affected the gel network, which was related to a change in electrostatic interactions. The results obtained showed that it is possible to produce protein gels from water-soluble protein-rich extracts from Chlorella sorokiniana, which may simplify application of protein extracts from this microalga in foods.

Comparative study of thermal gelation properties and molecular forces of actomyosin extracted from normal and pale, soft and exudative-like chicken breast meat.

ObjectiveThe objectives of this study were to investigate the thermal gelation properties and molecular forces of actomyosin extracted from two classes of chicken breast meat qualities (normal and pale, soft and exudative [PSE]-like) during heating process to further improve the understanding of the variations of functional properties between normal and PSE-like chicken breast meat.MethodsActomyosin was extracted from normal and PSE-like chicken breast meat and the gel strength, water-holding capacity (WHC), protein loss, particle size and distribution, dynamic rheology and protein thermal stability were determined, then turbidity, active sulfhydryl group contents, hydrophobicity and molecular forces during thermal-induced gelling formation were comparatively studied.ResultsSodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that protein profiles of actomyosin extracted from normal and PSE-like meat were not significantly different (p>0.05). Compared with normal actomyosin, PSE-like actomyosin had lower gel strength, WHC, particle size, less protein content involved in thermal gelation forming (p<0.05), and reduced onset temperature (To), thermal transition temperature (Td), storage modulus (G′) and loss modulus (G″). The turbidity, reactive sulfhydryl group of PSE-like actomyosin were higher when heated from 40°C to 60°C. Further heating to 80°C had lower transition from reactive sulfhydryl group into a disulfide bond and surface hydrophobicity. Molecular forces showed that hydrophobic interaction was the main force for heat-induced gel formation while both ionic and hydrogen bonds were different significantly between normal and PSE-like actomyosin (p<0.05).ConclusionThese changes in chemical groups and inter-molecular bonds affected protein-protein interaction and protein-water interaction and contributed to the inferior thermal gelation properties of PSE-like meat.

Effect of electron irradiation and heat on the structure of hairtail surimi

Abstract Hairtail surimi was treated with electron radiation and heat, the chemical interactions, thermal properties and the structural changes were determined. The chemical interaction data indicate that the contribution of disulfide bonds to heat-induced gel formation was decisive. Irradiation promoted the formation of disulfide bonds during the cooking. Differential scanning calorimetry showed that the myosin and actin thermal transitions of irradiated surimi shifted to lower temperatures. And the myosin thermal stability of irradiated surimi was lower than unirradiated surimi. The Fourier transform infrared and Raman results showed the irradiation and heat treatments decreased the α-helix structure content and increased β-sheet structure content. This study may provide useful information for the effect of irradiation on the surimi gel properties.

Solubility, Heat-Induced Gelation and Pepsin Susceptibility of Cruciferin Protein as Affected by Subunit Composition

This study examined the solubility, heat-induced gel formation ability, and pepsin susceptibility of cruciferin with mixed (wild type, WT) or identical subunits (CRUA, CRUB, or CRUC). All cruciferin species exhibited minimal solubility at pH 4.0 and slight solubility between pH 7.5 and 8, which was not influenced by the presence of NaCl. Increasing temperature to 90 °C did not affect the solubility of CRUC, but affected the solubility of other cruciferins between pH 4.0 and 8.0. Changes of secondary structure of cruciferins in a range of pH suggested structural alterations of the hexameric assembly might occur at pH 2.0. Near neutral pH was suitable to form heat-induced gels of WT, CRUA, and CRUB species. Although pH 2.0 was suitable for CRUC to form a strong gel, the same pH inhibited CRUB gel formation. High salt content (0.5 M NaCl) at neutral pH did not change the gel formation ability of WT, CRUA, or CRUB, but affected the gel characteristics. All cruciferins were hydrolyzed by pepsin, but the CRUC was degraded at a slower rate than the others. Trimer surface characteristics and the orientation and interaction of the HVR-I region of the hexameric assembly could be main structural factors for these property differences. Although the CRUC subunit showed properties that deviated from other species, the influence of CRUA and CRUB subunits seemed more prominent in the mixed subunit hexamer of WT.

Gel properties and molecular forces of lamb myofibrillar protein during heat induction at different pH values

The gel properties and molecular forces of the Aohan Merino lamb myofibrillar protein (MP) were investigated during heat induction at different pH levels. The effects of pH values (from 5.0 to 8.5) on the lamb MP gel textures and water-holding capacities were analyzed. The protein gels had the lowest water-holding capacity and a disordered microstructure at pH 5.5 (P<0.05) and had the lowest level of hardness at pH 6.5 (P<0.05). The hardness and water-holding capacity were found to be the highest at pH 8.0 (P<0.05), which coincided with a compact and ordered microstructure. At these three representative pH values, hydrophobic interactions were the main forces that were observed during gel formation, but the pH level also influenced the formation of ionic and hydrogen bonds. Different mechanisms of gel formation were therefore observed at different pH values. In conclusion, the formation of heat-induced gels with different properties was a result of the dominant molecular forces that are regulated by pH. These findings provide a theoretical basis for the innovation of heat-induced gel lamb products.

加熱誘導卵白アルブミンゲルの形成に及ぼす乳&lt;i&gt;α&lt;/i&gt;-カゼインおよびカプリン酸ナトリウム添加の影響

加熱誘導卵白アルブミンゲルの形成に及ぼす乳&lt;i&gt;α&lt;/i&gt;-カゼインおよびカプリン酸ナトリウム添加の影響

Improved heat stability by whey protein–surfactant interaction

One of the main changes that occur during heat treatment of milk is whey protein denaturation, which in its turn may lead to protein aggregation and gelation. In this contribution, the effect of lysophospholipids, the main components of lysolecithins, as well as alternative surfactants, on heat-induced whey protein aggregation has been studied. Hereby, attention was paid to the relation between polar lipid molecular structure (e.g. effect of alkyl chain length, effect of polar head group) and heat-stabilising properties. Residual protein determination in the supernatant obtained after centrifugation of heated whey protein solutions learned that whey protein aggregation was at least partly prevented in the presence of surfactants. As the short alkyl chain lysophospholipids were particularly effective heat stabilisers, hydrophilic surfactants seemed to be most effective, which may be ascribed to their higher critical aggregation concentration. Upon more severe heat treatment, protein aggregation was probed either in-situ by oscillatory rheology, or ex-situ by yield rheometry. As some surfactants significantly reduced the gel strength, or even prevented heat-induced gel formation, these experiments corroborated the heat-stabilising effect of hydrophilic surfactants. Nuclear Magnetic Resonance (NMR) enabled a more direct evaluation of the protein–surfactant interaction. A strong hydrophobic interaction between small molecular weight surfactants and whey proteins became obvious from the chemical shift of the surfactant hydrophobic groups in the NMR spectrum and could be quantified by pulsed field gradient NMR (pfg-NMR) diffusiometry. The results indicated that protein–surfactant interaction did not occur upon thermal denaturation, but already took place at room temperature. However, the effect of this interaction became mainly obvious during thermal treatment. Overall, this work indicated that bound surfactants largely minimise heat-induced protein intermolecular interactions and hence prevent heat-induced protein aggregation. As the surfactant molecular structure plays a decisive role, it follows that the heat stability of whey protein containing products may be optimised by appropriate selection of ingredients such as (lyso)phospholipids.

Heat-induced gel formation of plasma proteins: New insights by FTIR 2D correlation spectroscopy

Generalized 2D correlation spectroscopy (COS) has been applied to FTIR spectra of porcine plasma proteins to elucidate the sequence of events leading to pH- and/or thermal-induced protein unfolding and aggregation. Changes in the amide I′ region of the infrared spectra (in the pH range between 7.5 and 4.5, at 0.5 pH intervals) at 30 °C were especially evident as the pH approached the p I of serum albumin (4.8), with the globulin fraction in the plasma proteins undergoing denaturation prior to serum albumin. The effect of increasing temperature (from 30 to 90 °C, in increments of 5 °C) on the secondary structure of the plasma proteins at pHs in the range of 7.5–6.0 revealed that a decrease in alpha-helical structures is taken place previously to diminish native beta-sheets. So, the overall results of this study demonstrate that serum albumin and the globulin fraction differ in their sensitivity to pH and temperature.

Rheological Characteristics of Heat-Induced Custard Pudding Gels with High Antioxidative Activity

Custard pudding gels were prepared from fresh whole egg, milk and sugar. The effects of D-psicose (Psi), a non-calorie rare hexose, on the antioxidative activity and rheological properties of the custard pudding gels were investigated at different temperatures for comparison with those of control sugars (sucrose, Suc; D-fructose, Fru). The rheological behavior of the heat-induced pudding gels was evaluated by using breaking and creep tests. During the heat-induced gel formation, custard pudding containing Psi (15%, wt/wt) demonstrated a stronger breaking strength and higher viscoelasticity than those containing Fru and Suc. The thermodynamic parameters obtained from DSC indicated that the egg white (EW) proteins were made less thermally stable when heated in the presence of Psi than in the presence of Fru and Suc. These findings are consistent with enhanced aggregation of the EW solution in the presence of Psi. Furthermore, the Psi pudding gels possessed higher antioxidative activity than the control sugar pudding gels by using an analysis of the scavenging activity on DPPH radicals and the ferric-reducing antioxidative power. These results suggest that Psi favored cross-linking of Psi-protein molecules through the Maillard reaction which increased the formation of intermediate products to improve functionality. Custard pudding containing Psi could therefore be an effective functional sweet desert with high antioxidative activity and the outstanding gelling characteristics.

Physicochemical and textural properties of heat-induced pea protein isolate gels

Chemical and thermal properties of pea protein isolates (laboratory prepared or native; PPIn and commercial; PPIc) and textural properties of heat-set gels obtained from pea protein isolates were compared with homologous soy protein isolates (laboratory prepared, or native; SPIn and commercial; SPIc). The protein banding pattern resulting from electrophoresis separation confirmed the presence of predominant storage proteins of pea and soy seeds in the respective protein products. PPIc and SPIc had lower nitrogen solubility than their native counterparts, likely due to their denaturated state which was further confirmed by the absence of distinct endotherms in these commercial materials compared to the laboratory prepared ones. Addition of NaCl at 1.0–2.0% (w/w) to PPIn and SPIn slurries increased thermal transition temperatures for both proteins. The optimal conditions for formation of strong heat-induced gels from PPIc were 19.6% (w/w) protein content, pH 7.1, 2.0% (w/w) NaCl, and heating at 93 °C. SPIc gels prepared under the same conditions were stronger and more elastic than PPIc gels as denoted by texture indictors.

Heat-Induced Gel Formation by Soy Proteins at Neutral pH

Heat-induced gel formation by soy protein isolate at pH 7 is discussed. Different heating and cooling rates, heating times, and heating temperatures were used to elucidate the various processes that occur and to study the relative role of covalent and noncovalent protein interactions therein. Gel formation was followed by dynamic rheological measurements. Heat denaturation was a prerequisite for gel formation. The gelation temperature (84 degrees C) was just above the onset denaturation temperature of glycinin. The stiffness of the gels, measured as the elastic modulus, G', increased with the proportion of denatured protein. An increase in G' was also observed during prolonged heating at 90 degrees C. This increase is explained by the occurrence of rearrangements in the network structure and probably also by further incorporation of protein in the network. The increase in G' upon cooling was thermoreversible indicating that disulfide bond formation and rearrangements do not occur upon cooling.

Dynamic Viscoelastic Study on the Gelation Properties of β-Conglycinin-Rich and Glycinin-Rich Soybean Protein Isolates

Preheated soybean protein isolates (SPIs) were prepared from new soybean lines that have extremely different compositions of β-conglycinin and glycinin by a typical method for manufacturing commercial SPI. The gelation properties of these SPIs were investigated by dynamic viscoelastic measurements. The storage modulus G‘ of 12% SPI was measured at pH 7.0 when the temperature was increased from 30 to 80 °C and then lowered to 20 °C at 2 °C/min. Gelation properties of the preheated SPI were different from those of the non-pre-heated SPI. In the absence of NaCl, an increase in the storage modulus G‘ was observed for preheated β-conglycinin-rich SPI and preheated control SPI, but not for preheated glycinin-rich SPI. On the other hand, in the presence of 2.5% NaCl, an increase in the storage modulus G‘ was observed for all preheated SPIs in the order β-conglycinin-rich SPI > control SPI > glycinin-rich SPI. These results suggest that β-conglycinin plays an important role in the heat-induced gel formation of co...

Heat-Induced Gel Formation of .beta.-Lactoglobulin: A Study on the Secondary and Tertiary Structure As Followed by Circular Dichroism Spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeat-Induced Gel Formation of .beta.-Lactoglobulin: A Study on the Secondary and Tertiary Structure As Followed by Circular Dichroism SpectroscopyJames E. Matsuura and Mark C. ManningCite this: J. Agric. Food Chem. 1994, 42, 8, 1650–1656Publication Date (Print):August 1, 1994Publication History Published online1 May 2002Published inissue 1 August 1994https://doi.org/10.1021/jf00044a013RIGHTS & PERMISSIONSArticle Views789Altmetric-Citations74LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (735 KB) Get e-Alerts Get e-Alerts

Gelation of bovine serum albumin and β-lactoglobulin; effects of pH, salts and thiol reagents

The formation of heat-induced gels from bovine serum albumin (BSA) and β-lactoglobulin (β-Lg) under different conditions was studied. The minimum protein concentration required for formation of self-supporting gels in 100 m m Tris-HCl buffer (pH 8·0) following heating at 90°C for 15 min was 4% for BSA and 5% for β-Lg. Maximum gel hardness for both BSA and β-Lg occurred at pH 65. The hardness of β-Lg gels reached a maximum with the addition of 20–40 m m NaCl or 2 m m CaCl 2, while BSA was at a maximum with 5 m m CaCl 2 but were unaffected by NaCl. The hardness of β-Lg gels decreased slightly upon addition of various anions of sodium (between 50 and 100 m m). The effects followed the lyotropic series. Addition of N-ethyl-maleimide (NEM) decreased gel strength of BSA, while the gel hardness of β-Lg increased slightly with 5 m m NEM but decreased at higher NEM levels. Dithiothreitol (DTT), at 5 and 2 m m, respectively, enhanced gel hardness of BSA and β-Lg gels. Higher DTT levels significantly decreased gel hardness for both BSA and β-Lg. These results indicated that disulfide bonds are important in BSA gels, while electrostatic interactions and disulfide bonds are involved in the formation and maintenance of β-Lg gels.

THE FORMATION OF HEAT AND ENZYME INDUCED (PLASTEIN) GELS FROM PEPSIN-HYDROLYZED SOY PROTEIN ISOLATE

A gel prepared by heating pepsin-hydrolyzed soy protein isolate (HSPI) had a higher turbidity and viscosity and less solubility than did its starting hydrolyzate. The gelling characteristics of the heated hydrolyzate were possibly due to hydrophobic interactions, as opposed to peptide bond reformation. The presence of pepsin was found to be necessary for gel formation at 37°C but could be successfully replaced by heat. Incubation of the concentrated HSPI at 95°C for 30 min was optimal for heat-induced gel formation. When soy protein isolate (SPI) was hydrolyzed with papain or bacterial protease, little gelation occurred (either by heat or enzyme induced gelation treatments).

ホシザメ筋肉の加熱ゲル化反応に及ぼす温度の影響

ホシザメ筋肉の加熱ゲル化反応に及ぼす温度の影響