Effects of β‐glucans on properties of soya bean protein isolate thermal gels

The effects of concentration and molecular weight of oat β‐glucans on properties of soya bean protein isolate (SPI) thermal gels prepared by heating at 90℃for 30 min were investigated. Compared with control (free of β‐glucan) formulations, the presence of β‐glucans (0.5–1.5%, w/v) largely enhanced storage modulus (G′) and texture properties of SPI (12%, w/v) thermal gels measured by dynamic oscillatory rheometry and texture profile analysis, which were developed as increasing β‐glucan concentration and molecular weight. It is possible that β‐glucans could cause the formation of protein aggregates to produce gels through hydrophobic interactions. Mixed gel systems at low ionic strength showed higher G′ resulting from the lower denaturation temperature of SPI, which was beneficial to the formation of gel structure. In addition, although adding a certain amount of β‐glucan into SPI reduced water‐holding capacity of mixed gels, high molecular weight of β‐glucan improved their water‐holding capacity compared to control formulations attributed to the improvement of the structural integrity of the mixed gel network.     

The effect of pH and calcium ion on rheological behaviour of β‐lactoglobulin‐basil seed gum mixed gels

Effect of pH (4.5–7.5) and Ca²⁺ (0.01–0.5 m ) on gelation of single and mixed systems of 10% β‐lactoglobulin (BLG) and 1% basil seed gum (BSG) was investigated. The gelling point of BLG and BSG gels was strongly pH‐dependent, and stiffer gels formed at higher pH. The BLG gels were formed upon heating to 90 °C and reinforced on cooling to 20 °C; however, the gelation of BSG occurred at temperatures below 70 °C. By increasing Ca²⁺ concentration, storage modulus of BLG and BSG gels were increased, although pH had a greater effect than Ca²⁺. In contrast, mixed systems showed two distinct types of behaviour: BLG gel formation and BSG network, suggesting that phase‐separated gels were formed. In addition, higher strength was obtained for BLG‐BSG mixture at higher Ca²⁺ concentration.     

Effect of CMC Molecular Weight on Acid‐Induced Gelation of Heated WPI‐CMC Soluble Complex

Acid‐induced gelation properties of heated whey protein isolate (WPI) and carboxymethylcellulose (CMC) soluble complex were investigated as a function of CMC molecular weight (270, 680, and 750 kDa) and concentrations (0% to 0.125%). Heated WPI‐CMC soluble complex with 6% protein was made by heating biopolymers together at pH 7.0 and 85 °C for 30 min and diluted to 5% protein before acid‐induced gelation. Acid‐induced gel formed from heated WPI‐CMC complexes exhibited increased hardness and decreased water holding capacity with increasing CMC concentrations but gel strength decreased at higher CMC content. The highest gel strength was observed with CMC 750 k at 0.05%. Gels with low CMC concentration showed homogenous microstructure which was independent of CMC molecular weight, while increasing CMC concentration led to microphase separation with higher CMC molecular weight showing more extensive phase separation. When heated WPI‐CMC complexes were prepared at 9% protein the acid gels showed improved gel hardness and water holding capacity, which was supported by the more interconnected protein network with less porosity when compared to complexes heated at 6% protein. It is concluded that protein concentration and biopolymer ratio during complex formation are the major factors affecting gel properties while the effect of CMC molecular weight was less significant.     

Improving the quality of meat‐free sausages using κ‐carrageenan,konjac mannan and xanthan gum

High consumption of processed red meat can cause health issues. Therefore, production of high‐quality meat‐free food alternatives is necessary. The main objective of this study was to use hydrocolloids including κ‐carrageenan, konjac mannan and xanthan gum at 0, 0.3, 0.6, 1.0 and 1.5% w/w to improve the quality of meat‐free sausages formulated by soy protein isolated, texturised soy protein, corn starch, vegetable oil and spices. With the addition of the tested hydrocolloids, the lightness of the sausages improved. κ‐Carrageenan and konjac mannan significantly improved the water‐holding capacity and texture and reduced the cooking loss of the samples, while xanthan gum showed no considerable effect on these parameters. Konjac mannan and κ‐carrageenan (up to 0.6%) improved the general acceptability of the sausages, while inclusion of xanthan gum made no significant difference. Unlike xanthan gum, κ‐carrageenan followed by konjac mannan was highly successful in improving the overall quality of meat‐free sausages.     

Rheological and high gelling properties of mango (Mangifera indica) and ambarella (Spondias cytherea) peel pectins

Ambarella and mango peels are good sources of pectins (15–20%), with high degree of methylation (60–78%) and high molar masses. Ambarella and mango ( Améliorée and Mango varieties) peel pectins were extracted using HCl or oxalic acid/ammonium oxalate (OAAO). Purified pectins were analysed for their flow behaviour and phase diagrams were established at pH 3 as sucrose vs. pectin concentration. The gelation kinetics and mechanical spectra of these pectin gels were studied and compared to those of commercial citrus (lime) pectins. At a concentration of 1% (w/v), all pectic solutions had a shear thinning behaviour but at 0.6% (w/v), only OAAO-extracted pectins exhibited such behaviour. Phase diagrams showed that at pH 3, gelation of OAAO mango extracted pectins was possible at low polymer concentration (0.2%; w/w) for a sucrose concentration of 60% (w/w). OAAO-extracted pectins exhibited a higher gelling ability than HCl-extracted ones. Sucrose (45–50%) and pectin (0.2–0.6%) concentration had a deep impact on the gel strength. Our results enable to conclude that the OAAO extraction from mango and ambarella peels allowed the recovery of pectins that exhibit high gelling properties.     

Rheological and structural characterization of gels from whey protein hydrolysates/locust bean gum mixed systems

The gelling ability of whey proteins can be changed by limited hydrolysis and by the addition of other components such as polysaccharides. In this work the effect of the concentration of locust bean gum (LBG) on the heat-set gelation of aqueous whey protein hydrolysates (10% w/w) from pepsin and trypsin was assessed at pH 7.0. Whey protein concentrate (WPC) mild hydrolysis (up to 2.5% in the case of pepsin and 1.0% in the case of trypsin) ameliorates the gelling ability. The WPC synergism with LBG is affected by the protein hydrolysis. For a WPC concentration of 10% (w/w), no maximum value was found in the G′ dependence on LBG content in the case of the hydrolysates, unlike the intact WPC. However, for higher protein concentrations, the behaviour of gels from whey proteins or whey protein hydrolysates towards the presence of LBG becomes very similar. In this case, a small amount of LBG in the presence of salt leads to a big enhancement in the gel strength. Further increases in the LBG concentration led to a decrease in the gel strength.     

The effect of shear on the rheology and structure of heat‐induced whey protein gels

The influence of mechanical shearing on the small deformation properties and microstructure of heat‐induced whey protein gel has been studied. The viscoelastic properties of these gels at different concentrations of 10% and 20% (w/w) exposed to different shear rates of 0, 50, 100, 200 and 500 s^?1 during gelation were measured using dynamic oscillatory rheometry. The structure of both the shear treated and unsheared gels was then investigated using light microscopy. The results showed that the storage modulus of the gels at both concentrations was increased by increasing the shear rate exposure during gelation while the shear‐treated gels were more elastic and showed frequency‐independent behaviour. As the total protein concentration of the gel increased, the viscoelastic properties of the gels also increased significantly and the gels showed greater elasticity. The gels obtained from the higher shear rate exposure were stronger with higher elastic moduli at both protein concentrations. Images of the gels obtained using light microscopy showed that shearing resulted in phase separation and some aggregation in the structure of the gels at both concentrations. However, the shearing rates applied in this study were not enough to cause aggregation breakdown in the gel network.     

Effects of Cation Properties on Sol-gel Transition and Gel Properties of κ-carrageenan

The phase transition temperatures, rheological properties and gel‐network characteristics for gelation of κ‐carrageenan‐salt (NaCl, KCl and CaCl₂) solutions and their aged gels were investigated. The effectiveness of increasing gelling and gel‐melting temperatures at the salt concentrations examined followed the sequence of K⁺ > Ca2⁺ > Na⁺. This sequence was also true for the gel strength and the melting enthalpy (DH) of the most crosslinked junction zones of aged gels at low salt concentrations. Nonetheless, a different order (Ca⁺⁺ > K⁺ and Na⁺) was found for increasing storage modulus and gelation rate during early‐stage gelation, thermal hysteresis and the DH of aged gels in some salt‐carrageenan systems.     

Enhancement of freezing stability in mashed potatoes by the incorporation of kappa‐carrageenan and xanthan gum blends

BACKGROUND: To ameliorate the detrimental effects of freezing and thawing, blends of κ‐carrageenan (κ‐C) and xanthan gum (XG) were added to frozen/thawed mashed potatoes (F/TM potatoes). Product was tested by textural and rheological measurements, other quality parameters and sensory analyses. The effects of variation in levels of κ‐C (1.5–4.5 g kg^?1) and XG (0.5–2.5 g kg^?1) concentrations were studied. RESULTS: Instrumental measurements and sensory analyses indicated that 4.5 g kg^?1κ‐C and 2.5 g kg^?1 XG provided better thickening. κ‐C provided the appropriate texture, while XG imparted creaminess to the product, which could be associated with an increase in the amount of XG–water interactions. Addition of κ‐C had a major impact on textural properties, gel strength and viscoelastic behaviour, whereas XG influenced steady properties, colour, water‐holding capacity (WHC) and overall acceptability (OA). CONCLUSION: The OA of F/TM potatoes was mostly improved by addition of cryoprotectant blends, which is ascribed to improvement of F/TM potatoes texture by retarding starch retrogradation, increasing WHC, and enhancing the principal characteristics determining consumer acceptance. Creaminess was the most crucial factor for OA of the products. Addition of both polysaccharides at a low concentration (each cryoprotectant at 1.5 g kg^?1) is recommended. Copyright © 2009 Society of Chemical Industry     

Evaluation of the effect of Gleditsia amorphoides gum on the properties of rennet-induced milk protein gels

The study and characterisation of food gels obtained from phase-separated systems has gained interest since a wide variety of gel structures and textures can be developed. In this study, the phase and rheological behaviour of milk protein/espina corona gum (MP/ECG) mixtures were evaluated. These mixtures presented a segregative phase separation and a rheological behaviour proportional to the ECG concentration. Microstructural analysis, textural parameters and water-holding capacity of gels obtained from MP/ECG mixed systems using rennet as gelling agent were determined. At high ECG concentrations (≥0.05%, w/v), the gel microstructure changed from a coarse strand to a bicontinous microstructure. Such microstructural changes affected the textural parameters, firmness and break point, and the water-holding capacity of the gels. The results obtained in this work could be explained by the interplay between the segregative interaction of the biopolymers and the rennet-induced gelation rate.     

Milk-based Gels Made with κ-Carrageenan

ABSTRACT: The gel strength of κ‐carrageenan (0.1 to 0.4% w/w) ‐ reconstituted skim milk (2.5 to 20% w/w milk solids) mixtures was influenced by the concentrations of milk solids, κ‐carrageenan and cations. Particle size measurements showed that particle interactions in diluted skim milk‐κ‐carrageenan mixtures were dependent on the conformation of the κ‐carrageenan. Heat treatment of milk, resulting in alteration of the casein micelle, did not affect the interaction of κ‐carrageenan with casein in dilute solutions or the gel strength of milk‐κ‐carrageenan mixtures. κ‐Carrageenan must be available in the random coil form in solution, prior to cooling to its coil to helix transition temperature, for effective gelation of milk‐κ‐carrageenan mixtures.     

Formulation and in vitro evaluation of κ‐carrageenan‐pregelatinized starch‐based mucoadhesive gels containing miconazole

The aim of this work was to investigate the effects of using κ‐carrageenan (κ‐Carr) with pregelatinized starch (PGS) in the improvement of swelling and erosion behaviors of mucoadhesive gels containing 2% of miconazole. Polymer blends containing carrageenan and PGS were used for the formulation, and the effect of varying polymer concentrations on the drug release was studied. The matrices were prepared using different biopolymer (starch hydrogel) concentrations. Swelling and erosion characteristics of the matrices were carried out in various media and their impact on drug release were studied. The swelling action of the gel matrix was controlled by the rate of its hydration in the medium. Release studies have showed that the swelling and erosion of matrices influence the drug release. In addition, the presence of κ‐Carr in the gel formula improves the bioadhesive properties. The release data showed a good fit into the power law or Korsmeyer–Peppas equation indicating the combined effects of diffusion and erosion mechanisms of drug release. Most of the formulations released miconazole by an anomalous (non‐Fickian) transport mechanism, except those matrices that contained PGS alone which showed zero‐order release.     

Phase and Gelation Behavior of 2‐Hydroxy‐3‐(N,N‐dimethyl‐N‐dodecylammonium)propyloxy Starches

Some starches containing quaternary dimethylalkylammonium groups exhibit an unique phase behavior. A solid phase or gel phase is formed upon cooling, i.e. they are temperature‐responsive polymers. The aim of this study was to investigate the phase and gelation behavior of hydrophobically modified quaternary ammonium starch ethers in aqueous solutions. The mechanisms behind the phase behavior and hydrophobic character were investigated by light scattering (turbidity) and rheological measurements. A relatively large increase in the complex viscosity at higher concentrations was observed when the solutions were cooled to room temperature. The phase angle decreased drastically at a certain critical temperature. The decrease in the phase angle depended on the concentration of starch in solution, higher concentrations showing the greatest decrease and lower concentrations showing no significant change. Turbidity measurements indicated that a solid‐like highly concentrated phase was precipitated. The starch with zero net charge showed a larger increase in turbidity than the starch with a positive net charge, which indicates that particular precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules.     

Effects of inulin/oligofructose on the thermal stability and acid-induced gelation of soy proteins

ABSTRACT:  Differential scanning calorimetry (DSC) and dynamic oscillatory shear testing were performed to study the influence of inulin (Raftiline^® HP-gel and Raftiline^® ST-gel) and oligofructose (Raftilose^® P95) on the thermal stability and gelation (using glucono-δ-lactone [GDL] as a coagulant) of soy protein isolate (SPI) dispersions. Addition of 10% (w/v) inulin/oligofructose or sucrose increased ( P < 0.05) the peak denaturation temperatures ( T_m ) of 7S and 11S soy proteins in SPI dispersion (5%[w/v], pH 7.0) by an average of 1.9 and 2.3 °C, respectively. GDL induced SPI thermal gelation, and the gel rheology was affected by both the pH decline and the specific temperature of heating. Addition of inulin/oligofructose (8%, w/v) improved the gelling properties of preheated SPI dispersion (8%, w/v) coagulated with GDL, showing 14.4 to 45.6% increase ( P < 0.05) in gel rigidity ( G ' value) at the end of heating (81 °C). Microstructural examination revealed a denser protein cross-linking structure and reduced pore sizes in SPI gels containing inulin/oligofructose. In general, inulin was more capable of improving SPI gelation than oligofructose, suggesting that the degree of fructose polymerization in the fructans was of thermal and rheological importance.     

Impact of phase separation of whey proteins/hydroxypropylmethylcellulose mixtures on gelation dynamics and gels properties

This work constitutes a study of the impact of phase separation behaviour on the gels properties of a low viscosity hydroxypropylmethylcellulose and whey protein concentrate (WPC) mixed system. The phase separation was characterized by drawing the limit of thermodynamic compatibility, i.e. binodal curve, at pH 6.5 and room temperature (25 °C). Gelling properties were studied under thermodynamic compatibility (WPC 12% (w/w)/E50LV 0.25% (w/w) mixed system) and incompatibility conditions (WPC 12% (w/w)/E50LV 4% (w/w) and WPC 20% (w/w)/E50LV 4% (w/w) mixed systems)Under thermodynamic compatibility the WPC/E50LV mixed system shows gelling parameters similar to WPC. Confocal scanning laser microscopy (CSLM) micrographs showed a regular pattern of microdomains of proteins imbibed into E50LV matrix.Confocal microscopy of WPC/E50LV mixture under thermodynamic incompatibility offered details about the constitution of continuous and non-continuous phase and characteristics of non-continuous phase domains. Related to gelling parameters, the solid character upon heating was reinforced in mixed systems since they reflected the concentrating effect arising from phase separation. On the other hand, the solid character of gels upon cooling correlated with the component constituting the continuous phase, and the gelation temperature was similar to polysaccharide-rich phase predicted gelation temperature.Regarding to textural properties, the presence of the polysaccharide diminished the hardness of the mixed gels inducing less resistance to small and large deformation. WPC 20% (w/w)/E50LV 4% (w/w) mixed gel presented an interesting particulated macrostructure. This result would find application in food design and technology if the E50LV concentration is chosen to finely control the rate and extent of WPC aggregation-gelation-particulation. These results could be used in microparticulation or microencapsulation application of whey proteins.     

Strength of Protein Gels Prepared with Microbial Transglutaminase as Related to Reaction Conditions

Influence of gelling reaction conditions on the strength of several protein gels prepared with microbial transglutaminase (TGase) was investigated. A method was developed to gel proteins and measure gel breaking strength in a micro well plate. Enzyme concentration range for maximum gel breaking strength varied from 10 to 40 units/g protein. Maxima gel breaking strengths were achieved at 50°C for SPI, caseinate and gelatin and 65°C for egg yolk and egg white proteins. Optimum pH resulting in strong gels was pH 9 for SPI, caseinate, and egg yolk, and pH 6 for gelatin and egg white. Adjusting pH was promoted in egg white the formation of ?-(γ-glutamyl)lysine crosslinks and increased its gel breaking strength.     

Casein gelation under simultaneous action of transglutaminase and glucono‐δ‐lactone

Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono‐δ‐lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G ′) and gelation time of the gels were measured by oscillation rheometry, while protein cross‐linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G ′ values were interrelated with the formation of MTG‐induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration.     

Physicochemical properties and emulsion stabilization of rice dreg glutelin conjugated with κ‐carrageenan through Maillard reaction

BACKGROUND: Rice dreg is an underutilized source of cereal protein with good potential for application in the food industry. Glutelin represents about 850 g kg^?1 of total storage protein in rice dreg. The objective of this study was to characterize the physicochemical properties and emulsion stabilization of the Maillard type conjugate formed with rice dreg glutelin (RDG) and κ‐carrageenan (1:2 weight ratio) dry‐heated at 60 °C and 79% relative humidity for 24 h. RESULTS: Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and Fourier transform‐infrared analysis provided evidence on the formation of the Maillard type conjugation. Amino acid analysis suggested that the major locus during the Maillard reaction were lysine and arginine. Circular dichroism spectra showed decreasing amounts of α‐helix and β‐strand in the products with increment in the amount of turns and random coil. Conjugation with κ‐carrageenan could significantly improve solubility of RDG (P < 0.05). Measurements of mean droplet size and creaming stability in oil‐in‐water emulsions showed that the conjugate was more effective at stabilizing emulsions at low pH or in the presence of high ionic strength. CONCLUSION: The Maillard reaction can be successfully used as a coupling method for RDG and κ‐carrageenan to form the conjugate with improved solubility and emulsion stabilization. Copyright © 2012 Society of Chemical Industry     

Emulsifying properties of ovalbumin in mixtures with sulphated polysaccharides: effects of pH,ionic strength,heat and high‐pressure treatment

The influence of sulphated polysaccharides (dextran sulphate (DS), ι‐carrageenan (ι‐CAR) and κ‐carrageenan (κ‐CAR)) on the emulsifying properties of ovalbumin (OVA) has been investigated over a range of pressures and temperatures. Oil‐in‐water emulsions (10 g l⁻¹ protein, 200 ml l⁻¹ n‐tetradecane, pH 6.2) prepared with heat‐treated (80 °C for 10 min) mixtures of OVA + DS (1:0.25 by weight) had increased creaming stability but unchanged average droplet size compared to those made with untreated OVA and OVA + DS. Emulsions made with pressure‐processed (600 MPa for 20 min) OVA + DS (1:0.25 or 1:0.5 by weight) mixtures had the best emulsifying efficiency and stability. Under similar experimental conditions, replacement of DS with either ι‐ or κ‐CAR gave emulsions with larger droplets and more rapid serum separation, probably owing to depletion flocculation. High‐pressure treatment (600 MPa) of the OVA and mixed biopolymer solutions at pH 6.2 in the presence of salt (>0.04 M ) led to unstable emulsions, and so the protective effect of DS was lost. High‐pressure treatment (600 MPa) of emulsions prepared with native OVA or OVA + DS mixtures induced significant levels of flocculation, as indicated by changes in the average droplet size and creaming behaviour. © 2000 Society of Chemical Industry     

Improvement in emulsifying properties of soy protein isolate by conjugation with maltodextrin using high‐temperature,short‐time dry‐heating Maillard reaction

Soy protein isolate (SPI)–maltodextrin (MD) conjugates were synthesised using Maillard reaction under high‐temperature (90, 115 and 140 °C), short‐time (2 h) dry‐heating conditions. The loss of free amino groups in proteins and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) profile confirmed that SPI‐MD conjugates were formed and higher dry‐heated temperatures could increase the glycosylation degree. The emulsifying properties of SPI and SPI‐MD conjugates were evaluated in oil‐in‐water emulsions. The emulsions stabilised with SPI‐MD conjugates synthesised at 140 °C exhibited higher emulsifying stability and excellent storage stability against pH, ionic strength and thermal treatment compared with those synthesised at 90 °C, 115 °C and SPI stabilised emulsions. This might be due to a greater proportion of conjugated MD in SPI‐MD conjugates synthesised at 140 °C because of the higher glycosylation degree, and more conjugated MD on the droplet surface could provide steric effect and enhance the stability of the droplets in the emulsions.