Tabletted soy protein cold-set hydrogels as carriers of nutraceutical substances

The swelling of soy protein filamentous hydrogels and tablets thereof and the release of riboflavin from these drug delivery devices were investigated under simulated gastrointestinal conditions in the presence or absence of digestive proteases. Microscopic examination showed riboflavin arranged into crystals dispersed randomly throughout the hydrogel and the tablet powder. Swelling experiments showed a comparable behavior of water uptake for hydrogel and tablet at pH 1.2 as well as tablet at pH 7.5, featuring a low swelling rate. Hydrogel at intestinal pH began to shrink after 1 h, which coincided with a loss its structure. Riboflavin release was faster at pH 7.5 than at pH 1.2 for both devices. Swelling was the principal mechanism of riboflavin release from tablets at pH 7.5, while drug-polymer interactions slowed this release at pH 1.2. In the presence of pepsin at pH 1.2, both devices showed slow zero-order release of riboflavin for 6 h, while both were digested completely in the presence of pancreatin at pH 7.5. These results suggest that these tabletted hydrogels and the hydrogels themselves might both be useful for transporting bioactive molecules through the gastrointestinal tract and delivering them in the small intestine. Considering their non-synthetic nature, they should be of great interest for the development of innovative functional foods.     

燕麦蛋白-结冷胶冷诱导凝胶微观结构与控释特性的关联性研究

热变性后的燕麦蛋白(oat protein isolate,OPI)与结冷胶(gellan gum,GG)通过添加不同浓度的葡糖酸-δ-内酯(glucono-delta-lactone,GDL)形成OPI-GG冷诱导凝胶,通过质构分析、扫描电子显微镜、激光共聚焦显微镜以及傅里叶红外光谱,研究不同条件下形成的凝胶微结构以及分子构象的变化,探究不同凝胶微结构与凝胶控释特性的关联性。结果表明,在GG添加量为0.1%、pH 5时,凝胶硬度最大,随着GG浓度升高,凝胶硬度逐渐变弱。通过扫描电镜和激光共聚焦的观察可知OPI-GG凝胶可形成两种网络微结构,在pH 4和pH 5时,OPI与GG之间由于静电引力使其相互作用力增强,形成致密且均匀的单网络微结构;在pH 6和pH 7时,OPI与GG由于静电斥力的作用产生相分离,从而形成双网络结构。具有不同微结构的OPI-GG凝胶可作为基质包埋核黄素,双网络结构的凝胶可有效提高核黄素的包埋率(75%),其在pH 1.2磷酸缓冲溶液(phosphate buffer saline,PBS)中浸泡2 h后核黄素的释放率为33%;致密的单网络结构OPI-GG凝胶包埋率为61%,在pH1.2 PBS中可有效阻止核黄素的释放,其释放率为18%,并在pH 7.4 PBS中使核黄素逐步释放,8 h后释放率为53%。该研究结果表明,在中性条件下制备的OPI-GG双网络结构冷凝胶具有较好的核黄素包埋能力,在酸性条件下制备的OPI-GG单网络冷凝胶具有较好的控释能力,因此,不同微结构的OPI-GG冷凝胶具有作为营养素包埋和递送体系的潜力。     

Mixed gels of gelatin and whey proteins, formed by combining temperature and high pressure

Mixed and pure gels of gelatin and whey protein concentrate (WPC) were formed by using temperature and high pressure simultaneously. Combining these gel formation methods enables the two polymer networks to set at the same time. The microstructure of the gels was studied by means of light microscopy and transmission electron microscopy, and the rheological properties by means of dynamic oscillatory measurements and tensile tests. The pH values investigated were 5.4, 6.8 and 7.5. The isoelectric point of the WPC is around pH 5.2 and that of gelatin between pH 7.5 and 9. At pH 5.4, the mixed gel formed a phase-separated system, with a gelatin continuous network and spherical inclusions of the WPC. The storage modulus (G) of the mixed gel was similar to that of a pure gelatin gel. At pH6.8, the mixed gel formed a phase-separated system, composed of an aggregated network and a phase with fine strands. The aggregated network proved to be made up of both gelatin and WPC, and the fine strands were formed of gelatin. The mixed gel at pH 6.8 showed a high G compared with the pure gels, which decreased significantly when the gelatin phase melted. At pH 7.5 the mixed gel was composed of one single aggregated network, in which gelatin and WPC were homogeneously distributed. It was impossible to distinguish the gelatin from the WPC in the mixed network. The mixed gel at pH 7.5 showed a significantly higher G than the pure gels. As the gelatin phase was melted out for the mixed gel, a large decrease in G was observed. The pure gelatin gels, formed by a temperature decrease under high pressure, proved to be pH-dependent, showing an increase in aggregation as the pH increased from 5.4 to 7.5. A fine-stranded, transparent gelatin gel was formed at pH 5.4, while an aggregated, opaque gel was formed at pH 7.5. The stress at fracture for the gelatin gels decreased as the aggregation, and consequently the pore size, increased.     

Mixed gels of fine-stranded and particulate networks of gelatin and whey proteins

Mixed gels of gelatin and whey protein concentrate were investigated, as well as their pure systems, by tensile tests and by dynamic oscillatory measurements. The systems were studied for homogeneous particulate whey protein gels at pH 5.4 and for inhomogeneous particulate whey protein gels at pH 4.6. The influence on the systems of the Bloom number of the gelatin component has also been investigated. Results of the fracture properties, such as stress and strain at fracture, indicate a transition in rheological properties. Results of the elastic modulus, obtained by tensile measurements, as well as the storage modulus, obtained by dynamic oscillatory measurements, both agree with predictions for phase inversions from the Takayanagi models as modified by Clark, which are in agreement with the fracture properties. The transition points are different for the different mixed gel series but take place between 1 and 3 wt% gelatin and 8 wt% whey protein concentrate, depending on factors such as the microstructure of the whey protein concentrate. Dynamic oscillatory measurements showed that gel formation of whey protein concentrate is unaffected by the presence of gelatin, which is in agreement with light microscopy results. Light microscopy revealed that the mixed gel systems were bicontinuous and that the whey protein network structure was unaffected by the presence of gelatin. It is postulated that the predicted phase inversions of the mixed gels are due to a shift in rheological properties without any phase inversions in the microstructure.     

Influence of ultrasound and enzymatic cross-linking on freeze-thaw stability and release properties of whey protein isolate hydrogel

This study investigated the effect of ultrasound and enzymatic cross-linking on the freeze-thaw (FT) stability and release properties of whey protein isolate hydrogels. We evaluated the FT stability by the changes in the microstructure, riboflavin retention, syneresis, water holding capacity (WHC), and texture of gels subjected to 3 FT cycles. High-intensity ultrasound (HUS) and transglutaminase (TGase)-mediated cross-linking improved the FT stability of whey protein isolate hydrogels loaded with riboflavin (WPISAR), as demonstrated by a more uniform and denser porous structure, significantly higher riboflavin retention, WHC, and textural properties, and lower syneresis after 3 FT cycles than those of untreated hydrogels. Furthermore, HUS- and TGase-mediated cross-linking decreased protein erosion and swelling ratio of WPISAR in simulated gastrointestinal fluids (SGIF) and reduced the riboflavin release rate in SGIF both with and without the addition of digestive enzymes. After 3 FT cycles, faster riboflavin release occurred due to a more porous structure induced by ice crystal formation compared with their unfrozen counterparts as detected by confocal laser scanning microscopy. High-intensity ultrasound- and TGase-mediated cross-linking alleviated the FT-induced faster riboflavin release rate in SGIF. High-intensity ultrasound- and TGase-treated gel samples showed that both diffusion and network erosion were responsible for riboflavin release regardless of FT. These results suggest that HUS- and TGase-mediated cross-linking improved the FT stability of WPISAR with a high riboflavin retention, and might be a good candidate as a controlled-release vehicle for riboflavin delivery to overcome undesired FT processing.     

Viscoelastic and fragmentation characters of model bolus from polysaccharide gels after instrumental mastication

Model bolus from polysaccharide gels was investigated by the stress-relaxation tests and particulate size analyses. Using two gelling agents, gellan gum and a composite of gellan/psyllium seed gums, gels with different physical properties (i.e., elastic gellan single gels and plastic composite gels) and gel hardness were prepared. Gels were masticated instrumentally in the presence or absence of artificial saliva to prepare model bolus. Data from the stress-relaxation tests analyzed by 5-element mechanical model showed that difference between two Maxwell-bodies in the elasticity for the composite gels was generally smaller than that for gellan single gels when compared at equivalent gel hardness and was less influenced by the addition level of saliva. For each gel sample, cumulative particulate size distribution of model bolus was reduced logarithmically with a normal curve regardless of the addition level of saliva. Mean particulate size of model bolus from the composite gels was generally larger than that for gellan single gels when compared at equivalent gel hardness and was less influenced by the addition level of saliva. Based on the particulate size distribution of model bolus, coefficients of skewness and kurtosis calculated for the composite gels tended to be larger than those for gellan single gels when compared at equivalent gel hardness. Results indicated higher structural homogeneity of model bolus from the composite gels, which is related to higher miscibility with saliva. Structural homogeneity should be the key for texture design of nursing-care foods, particularly for dysphagia.     

Maillard-Type Cross-Linked Soy Protein Hydrogels as Devices for the Release of Ionic Compounds: An In Vitro Study

The contribution of cross-linking degree on soy protein hydrogels release properties was studied in vitro using a Maillard-type cross linker and amaranth and methylene blue as tracers. Increased cross-linker concentration or salt presence in the gel generally led to decreased swelling/release rates in the absence of digestive enzyme. Surprisingly, at pH 1.2, amaranth was not released. In the presence of pepsin or pancreatin, increased cross-linker concentration or the presence of salt in the gel was also shown to decrease compound release, particularly for methylene blue at pH 7.5. Compound release was strongly dependent on medium pH and compound ionic status. Amaranth, an anionic molecule, showed slower release in gastric conditions, whereas methylene blue, a cationic drug, showed the opposite result. Partition coefficients of these compounds matched these results. This paper demonstrates the potential of food proteins as carriers of ionic compounds.     

Heat-induced gelation of porcine blood plasma proteins as affected by pH

Porcine plasma is a by-product of the meat industry that can be used as a food ingredient. It is a protein mixture, hence its composition can be modified to meet specific functionality requirements. In the present paper, the gelation properties of plasma and its two major fractions (serum and albumin) have been studied at pH 4.5, 6.0 and 7.5. Polyacrylamide gel electrophoresis (SDS-PAGE) revealed that albumin was the constituent that remained soluble to a larger extent during heat-treatments, and that acidic coagulation occurred at pH 4.5, making weak interactions the predominating ones between protein aggregates. Differential scanning calorimetry (DSC) and rheological tests showed that both the thermal stability and the gelation point of protein solutions were lower as pH decreased. The textural properties and water-holding capacities of plasma and albumin gels were more pH-dependent than serum. Albumin gels were the weakest and those of plasma at pH 7.5, the strongest. It has been determined that interactions between protein fractions play a key role in the gelling properties due to synergistic effects. This knowledge should be useful in the engineering of a plasma derivative product designed for specific food requirements, by reformulating its natural composition and enhanced by controlling pH.     

The roles of disulphide and non-covalent bonding in the functional properties of heat-induced whey protein gels

Heat-induced gelation (80 degrees C, 30 min or 85 degrees C, 60 min) of whey protein concentrate (WPC) solutions was studied using transmission electron microscopy (TEM), dynamic rheology and polyacrylamide gel electrophoresis (PAGE). The WPC solutions (150 g/kg, pH 6.9) were prepared by dispersing WPC powder in water (control), 10 g/kg sodium dodecyl sulphate (SDS) solution or 10 mM-dithiothreitol (DTT) solution. The WPC gels containing SDS were more translucent than the control gels, which were slightly more translucent than the gels containing DTT. TEM analyses showed that the SDS-gels had finer aggregate structure (approximately equal to 10 nm) than the control gels (approximately equal to 100 nm), whereas the DTT-gels had a more particulate structure (approximately equal to 200 to 300 nm). Dynamic rheology measurements showed that the control WPC gels had storage modulus (G) values (approximately equal to 13,500 Pa) that were approximately equal to 25 times higher than those of the SDS-gels (approximately equal to 550 Pa) and less than half those of the DTT-gels after cooling. Compression tests showed that the DTT-gels were more rigid and more brittle than the control gels, whereas the SDS-gels were softer and more rubbery than either the control gels or the DTT-gels. PAGE analyses of WPC gel samples revealed that the control WPC solutions heated at 85 degrees C for 10 min contained both disulphide bonds and non-covalent linkages. In both the SDS-solutions and the DTT-solutions, the denatured whey protein molecules were in the form of monomers or small aggregates. It is likely that, on more extended heating, more disulphide linkages were formed in the SDS-gels whereas more hydrophobic aggregates were formed in the DTT-gels. These results demonstrate that the properties of heat-induced WPC gels are strongly influenced by non-covalent bonding. Intermolecular disulphide bonds appeared to give the rubbery nature of heat-induced WPC gels whereas non-covalent bonds their rigidity and brittle texture.     

Aerated whey protein gels as a controlled release system of creatine investigated in an artificial stomach

A controlled creatine-release system has been developed from whey protein-based gels. Their functionalization was carried out by aeration and sodium ions induced “cold gelation” processes. The effect of protein concentration in the aerated whey protein gels at pH 7.0 and 8.0 was analyzed. Physicochemical properties of the aerated gels were evaluated. It was possible to obtain the ions induced whey protein aerated gel with well distributed creatine and different microstructure as well as rheological properties. Different protein concentrations and pH enabled obtaining gels with different rheological properties, texture, air fraction, diameter of air bubbles, microstructure and surface roughness. An increase in the protein concentration enhanced the hardness of the samples, regardless of their pH. The mechanical strength of gels prepared at pH 8 were higher than those obtained at pH 7, as was manifested by the smaller storage modulus of the latter. The former gel exhibited a microstructure between particulate and fine-stranded. A stronger gel matrix produced smaller air bubbles. Aerated gels produced at pH 7.0 had higher roughness than those obtained at pH 8.0. Optimal conditions for inclusion of air bubbles into the gel matrix were: 9% protein concentration at pH 8.0 and this aerated gel was selected for digestion in the artificial stomach. There is a small conversion of creatine to creatinine in the artificial stomach digestion process (9.6% after 6 h). The diffusion of creatine crystals from the aerated gel matrix was the mechanism responsible for the release process. Aerated whey protein gels can be used as matrices for time extended releasing of creatine in the stomach.     

Rheology of whey protein isolate-xanthan mixed solutions and gels. Effect of pH and xanthan concentration

Flow properties at pH 5.5-7.5 of whey protein isolate (WPI)-xanthan solutions containing 0-0.5 w/w% xanthan were studied by viscosimetry, although rigidity and fracture properties of the corresponding heat-set gels (90°C, 30 min) were determined by uniaxial compression. All the studied solutions displayed generalized shearthinning flow behaviour. Synergistic WPI-xanthan interactions has been revealed by observing that rheological parameters [σ_msf, K, n, η (γ)] characterizing blends were larger than those calculated from the two separated solutions. Such a behaviour was attributed to segregative phase separation of whey proteins and xanthan. Effects of xanthan on WPI-xanthan gel properties both depended on pH and xanthan concentration. Simultaneous increased xanthan concentration and decreased pH inhibited gelation of WPI-xanthan blends. Regarding gel strength, synergistic WPI-xanthan interactions were observed at pH >7.0 and low xanthan concentration (0.05 or 0.1 w/w%). Antagonism between the two macromolecules occurred at low xanthan concentration and pH ≤6.5, and high xanthan concentration (0.2 or 0.5 w/w%) at all pH tested. Low xanthan concentration rendered mixed gels more brittle than protein gels, and high xanthan concentration decreased pH effects on gel stress-strain relationships. The balance between strong thermal aggregation of concentrated whey proteins - in presence of incompatible xanthan -, high viscosity of blends and repulsive surface forces of protein molecules was thought to be at the origin of WPI-xanthan gel mechanical properties.     

RHEOLOGY OF ACID-INDUCED SODIUM CASEINATE STABILIZED EMULSION GELS

The storage modulus G', loss modulus G", and phase angle δ of acidinduced sodium caseinate emulsion gels were measured at 25C for a certain period of time after the addition of glucono-δ-lactone (GDL). Comparison between pure protein gels and emulsion gels revealed that the presence of emulsion droplets greatly enhanced the gel strength. Acidification by mixing an emulsion with a GDL solution caused immediate gelation but the emulsion gel had similar mechanical properties to the gel formed by direct addition of GDL granules. The viscoelasticity of the gel was strongly related to the pH value of the system. There was no evidence for a three-dimensional network when the pH value was higher than 5.8 or lower than 3.2. The largest storage and loss moduli were observed for gels formed at pH values near the isoelectric point of sodium caseinate (pH 4.6). Rheological differences for gels made at different pH values became distinguishable at low frequencies, where a much smaller phase angle was determined for a gel made at a pH value below the isoelectric point. Partial recovery of the three-dimensional gel network was observed for disrupted gels formed at a pH near the isoelectric point.     

Formation of Elastic Whey Protein Gels at Low pH by Acid Equilibration

Abstract: Whey protein gels have a weak/brittle texture when formed at pH ≤ 4.5, yet this pH is required to produce a high-protein, shelf-stable product. We investigated if gels could be made under conditions that produced strong/elastic textural properties then adjusted to pH ≤ 4.5 and maintain textural properties. Gels were initially formed at 15% w/w protein (pH 7.5). Equilibration in acid solutions caused gel swelling and lowered pH because of the diffusion of water and H⁺ into the gels. The type and concentration of acid, and presence of other ions, in the equilibrating solutions influenced pH, swelling ratio, and fracture properties of the gels. Swelling of gels decreased fracture stress (because of decreased protein network density) but caused little change to fracture strain, thus maintaining a desirable strong/elastic fracture pattern. We have shown that whey protein isolate gels can be made at pH ≤ 4.5 with a strong/elastic fracture pattern and the magnitude of this pattern can be altered by varying the acid type, acid concentration, pH of equilibrating solution, and equilibrating time. Practical Application: Low-pH shelf-stable whey protein gels having the strong/elastic texture can be made by forming gels at high pH and equilibrating in acid solutions. Acid equilibration causes the gel to swell and lower the gel pH. Moreover, gel properties can be altered by varying the acid type, acid concentration, pH of equilibrating solution, and equilibrating time.     

EFFECTS OF pH ON WHEY PROTEIN CONCENTRATE GEL PROPERTIES: COMPARISONS BETWEEN SMALL DEFORMATION (DYNAMIC) AND LARGE DEFORMATION (FAILURE) TESTING

The effects of pH on the properties of gels prepared from commercially available whey protein concentrate were investigated by nondestructive dynamic shear testing with a Bohlin Rheometer and by large deformation compression, tension and penetration tests with an Instron Universal Testing Machine. Dynamic storage modulus, G', and the slopes of force-deformation curves from all three types of large deformation test exhibited maxima at or near both pH 4 and pH 7. Electrostatic interactions were the dominant factor in explaining this behaviour. Failure displacements in the large deformation tests generally increased with increase in pH. It is proposed that the formation of disulphide bonds at pH values above 6.5 is the dominant factor in explaining this behaviour. Failure forces in the large deformation tests remained low up to pH 6.5, increased rapidly to a maximum at pH 7–7.5 and then decreased again. The variation in both electrostatic interactions and disulphide bonds with pH is necessary to explain this behaviour. The combination of penetration failure force, penetration failure displacement and penetration rigidity (slope of force-displacement curve) provided as much qualitative understanding of the variation of gel properties with pH as similar information from any other single test.     

pH值对11S球蛋白结构与凝胶性的影响

研究了豫豆-25 11S球蛋白凝胶质构特性与pH值的关系。结果表明:pH值对豫豆-25 11S球蛋白凝胶的形成及质构特性影响较大,酸性条件下的凝胶与碱性条件下的有较大的差异。扫描电子显微镜(SEM)观察及傅立叶交换红外光谱(FTIR)分析显示:在远离等电点的碱性条件下,11S球蛋白凝胶具有较高有序性的微观结构,它们的微观结构均匀,只有少量的聚合物;酸性条件下的凝胶的微观结构有序性低于碱性条件下的凝胶,离等电点较近pH的凝胶聚合物较多,微观结构有序性低;pH4.15的凝胶要比pH7.5的含有更多的无规则卷曲结构。凝胶蛋白二级结构中无规则卷曲向有序结构的转化,微观结构趋于有序。     

Involvement of Disulfide Bonds in Bovine β-Lactoglobulin B Gels Set Thermally at Various pH

To obtain information on forces important for maintenance of the structure of heat-set β-lactoglobulin gels, gels set from pure β-lactoglobulin at pH 3.0, 5.0, and 7.0 were solubilized in dissociating buffers, and solubilized material was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion high performance liquid chromatography. The gel formed at pH 7.0 was largely soluble in urea (or SDS), and this gel seemed to be built from covalently linked soluble aggregates, associating into a gel network mainly by strong noncovalent interactions. The gel set at pH 5.0 was solubilized only in the presence of a reducing agent, indicating that this gel structure was supported mainly by covalent disulfide bonds. The gel set at pH 3.0 was almost completely solubilized in SDS or urea without a reducing agent, showing the importance of noncovalent interactions in maintaining the gel structure.     

How micro-phase separation alters the heating rate effects on globular protein gelation

This study was conducted to determine how the combination of heating rate and pH can be used to alter viscoelastic properties and microstructure of egg white protein and whey protein isolate gels. Protein solutions (1% to 7% w/v protein, pH 3.0 to 8.5) were heated using a range of heating rates (0.2 to 60 °C/min) to achieve a final temperature of 80 °C. The gelation process and viscoelastic properties of formed gels were evaluated using small strain rheology. Single phase or micro-phase separated solution conditions were determined by confocal laser scanning microscopy. In the single phase region, gels prepared by the faster heating rates had the lowest rigidity at 80 °C; however, a common G' was achieved after holding for 4 h at 80 °C . On the other hand, under micro-phase separation conditions, faster heating rates allowed phase separated particles to be frozen in the network prior to precipitation. Thus, gels produced by slower heating rates had lower rigidities than gels produced by faster heating rates. The effect of heating rate appears to depend on if the solution is under single phase or micro-phase separated conditions. PRACTICAL APPLICATION: The effect of heating rate and/or time on protein gel firmness can be explained based on protein charge. When proteins have a high net negative charge and form soluble aggregates, there is no heating rate effect and gels with equal firmness will be formed if given enough time. In contrast, when electrostatic repulsion is low, there is a competition between protein precipitation and gel formation; thus, a faster heating rate produces a firmer gel.     

多糖基颗粒稳定的Pickering乳液凝胶研究进展

近年来,乳液凝胶由于能够提高乳液稳定性、保护生物活性物质、控制生物活性物质释放等优点,引起了人们极大的兴趣.多糖基颗粒稳定的Pickering乳液凝胶是指将多糖基颗粒稳定的Pickering乳液嵌入凝胶网络中,或者由多糖基颗粒稳定的Pickering乳液液滴聚集、相互作用形成连续的乳液颗粒型凝胶网络结构.这种乳液凝胶具...     

Rheological,surface and colorbvietric properties of egg albumen gel affected by pH

Abstract

Studies were conducted to evaluate the effects of albumen at naturally existing pH ranges on the functional and gel characteristics. Albumen was obtained from freshly laid shell eggs. The pH of albumen was altered using either IN NaOH or IN HC1 to obtain a pH of 7.5, 8.0, 8.5, 9.0, 9.5 and 10.0. The altered albumen was tested for its foaming capacity (FC), foam stability (FS), and bake volume (BV). Albumen gels were prepared and tested for firmness (FM), strain at failure (NF), and stress at failure (SF) as well as their color attributes (Hunter L, a, and b). In general, FC and BV of the albumen decreased (P<0.05) as the pH increased. The BV of the albumen was affected by FS than FC for all the adjusted pH ranges. A denser structure was observed for albumen gels as the pH increased. The FM, NF and SF of albumen gels increased, and Hunter L and a values decreased with the increasing adjusted pH. The FM, NF, SF and Hunter L value of albumen gel could be used as quality indicators in evaluating the changes of texture and color with pH.     

Gel formation by β-conglycinin and glycinin and their mixtures

Gel formation and gel properties of β-conglycinin, glycinin and their mixtures were studied as a function of pH using small and large deformation rheology and differential scanning calorimetry. We conclude that heat denaturation is a prerequisite for gel formation. Gelation temperatures of β-conglycinin were lower than those of glycinin and more dependent on protein concentration. At pH 7.6, protein solutions gelled at a higher temperature than at pH 3.8.Glycinin gels were stiffer than β-conglycinin gels at the same pH and protein concentration, and fractured at a higher strain and stress. At pH 7.6, G′ is lower than at pH 3.8 for both proteins and the gels could be deformed to a larger extent. Based on the appearance of the gels (turbid at pH 7.6, white at pH 3.8) and the fracture properties, we conclude that different network structures are formed as a function of pH. The reason why glycinin gives a better gel than β-conglycinin is believed to be due to a difference in network structure as well as in strength of interaction between the protein molecules.Mixing of both soy proteins resulted in improved gelling properties at pH 3.8. The elastic modulus of the mixture was larger than the weighed sum of the separate contributions. Furthermore, mixing reduced the protein dispersability at pH 7.6. This strongly indicates the presence of an interaction between the proteins. Gels of the 1:1 mixture (pH 3.8) had a fracture stress and strain in between those of the gels of the separate proteins.