Rheological interactions between Lallemantia royleana seed extract and selected food hydrocolloids

BACKGROUND: Lallemantia royleana (Balangu) is a mucilaginous endemic plant which is grown in different regions of world. The flow behaviour of Balangu seed extract (BSE) and its mixture with xanthan, guar and locust bean gums at 1:3, 1:1 and 3:1 ratios, in addition to control samples (0% BSE), were evaluated. To describe the rheological properties of samples, the power law model was fitted on apparent viscosity–shear rate data. To evaluate the interaction between BSE and selected hydrocolloids in dilute solutions, the relative viscosity was also investigated. RESULTS: There was no significant difference between the consistency coefficient of guar and locust bean solutions and their blends substituted with 250 g kg^?1 BSE. The BSE–xanthan mixture at 1:3 and 1:1 ratios had consistency index equal to xanthan solution. BSE–locust bean gum at all ratios, BSE–xanthan at 1:3 ratio and BSE–guar gum at 1:1 and 3:1 ratios indicated relative viscosity lower than values calculated assuming no interaction. The intrinsic viscosity value of BSE was determined 3.50 dL g^?1. CONCLUSION: The apparent viscosities of BSE, selected hydrocolloids and their blends were the same at a shear rate of 293 s^?1 and the commercial gums can be substituted by 250 g kg^?1 and 500 g kg^?1 BSE. Copyright © 2011 Society of Chemical Industry     

Comparison of the effects of gums on dynamic rheological properties of acetylated sweet potato starch

Dynamic rheological properties of acetylated sweet potato starch (ASPS) pastes mixed with 3 commercial gums (guar gum, locust bean gum, and xanthan gum) were investigated at different gum concentrations. The dynamic moduli of the ASPS-gum mixtures were higher than those of the control, and they increased with an increase in gum concentration. In particular, the G′ value of xanthan and G″ value of guar gum at a 0.6% gum concentration were much higher as compared to those of other mixtures. Tan δ values of ASPS-xanthan mixtures were much lower than those of other samples, indicating that the elastic properties in the ASPS-gum mixture systems were strongly affected by the additions of xanthan. These results suggest that the presence of gums in ASPS modifies the viscoelastic properties, and that these modifications are dependent on the gum type and gum concentration.     

Viscosity of guar gum and xanthan/guar gum mixture solutions

The viscosity of diluted guar gum solutions and the viscosity of xanthan and guar gum mixture solutions have been studied. Guar gum solutions showed pseudoplastic behaviour. Apparent viscosity increased with gum concentration and decreased with the temperature at which viscosity was measured. A maximum in the plot of viscosity versus increasing dissolution temperature was observed at 60 °C. This behaviour was related to differences in molecular structure of the polymers solved at different temperatures. Mixtures of xanthan and guar gum showed a higher combined viscosity than that occurring in each separate gum. This synergistic interaction was affected by the gum ratio in the mixture and dissolution temperature of both gums. The effect of polysaccharide concentration (1.0, 1.5 and 2.0 kg m⁻³), xanthan/guar gum ratio (1/5, 4/2, 3/3, 4/2 and 5/1) and dissolution temperature (25, 40, 60 and 80 °C for both gums) on the viscosity of solutions of mixtures were studied. The highest viscosities were observed when 2.0 kg m⁻³ gum concentration was used together with a ratio of xanthan/guar gum of 3/3 (w/w) and dissolution temperature of 40 and 80 °C for xanthan and guar gum, respectively. © 2000 Society of Chemical Industry     

Rheology of Mixed Systems of Sweet Potato Starch and Galactomannans

The effect of galactomannans (guar gum and locust bean gum) at different concentrations (0, 0.2, 0.4 and 0.6%, w/w) on rheological properties of sweet potato starch (SPS) was studied. The flow behaviors of SPS‐galactomannan mixtures were determined from the rheological parameters of power law and Casson models. The SPS‐galactomannan mixtures had high shear‐thinning fluid characteristics (n = 0.30‐0.36) exhibiting yield stress at 25°C. The presence of galactomannans resulted in the increase in consistency index (K), apparent viscosity (η_a,100) and Casson yield stress (σ_oc). In the temperature range of 25‐70°C, the mixtures followed the Arrhenius temperature relationship. Dynamic rheological tests at 25°C indicated that the SPS‐galactomannan mixtures had weak gel‐like behavior with storage moduli (G′) higher than loss moduli (G") over most of the frequency range (0.63‐62.8 rad/s) with frequency dependency. The magnitudes of dynamic moduli (G′, G" and η*) of the SPS‐galactomannan mixtures were higher than those of the control (0% gum), and increased with an increase in gum concentration. The tan δ (ratio of G"/G′) values (0.41‐0.46) of SPS‐guar gum mixtures were much lower than those (0.50‐0.63) of SPS‐locust bean gum mixtures, indicating that there was a more pronounced effect of guar gum on the elastic properties of SPS.     

Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (η_a,100) and yield stress (σ_oc) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η_a,100) was described by the Arrhenius equation. The activation energy values (E_a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that (E_a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E_a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage (G′) and loss (G′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G′ and G′′ increased with the increase in gum concentration. Dynamic rheological data of ln (G′, G′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G′ greater than G′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.     

Rheological behaviors of hydroxypropylated sweet potato starches influenced by guar,locust bean,and xanthan gums

This study examined the steady flow and dynamic rheological behaviors of hydroxypropylated sweet potato starch (HPSPS) pastes mixed with guar gum (GG), locust bean gum (LBG), and xanthan gum (XG) at different concentrations (0, 0.3, and 0.6%). The HPSPS–gum mixtures had higher shear‐thinning fluid characteristics than the control (0% gum) at 25°C. The addition of the gums resulted in an increase in the consistency index (K) and apparent viscosity (η_a,100). The dynamic moduli (G′, G″) and complex viscosity (η*) values of the HPSPS–gum mixtures were higher than those of the control, and they increased with an increase in gum concentration. In particular, the presence of XG at 0.6% in the HPSPS–gum mixture systems gave rise to the greatest viscoelastic properties among the gums examined at different concentrations. The tan δ (ratio of G″/G′) values (0.35–0.57) of the HPSPS–GG and HPSPS–XG mixtures were much lower than those of the control (0.82) and HPSPS–LBG (0.88–1.06), indicating that the elastic properties in the HPSPS–gum mixture systems were strongly affected by the additions of GG and XG. These steady flow and dynamic rheological parameters indicated there were synergistic interactions between the HPSPS and gums. The synergistic effects of the gums and modified starch were hypothesized by considering the molecular incompatibility and molecular interactions between the gums and HPSPS.     

Rheological behaviour of pullulanase-treated guar galactomannan on co-gelation with xanthan

The present study involves the use of non-specific enzyme pullulanase (from Bacillus acidopullulyticus) to remove galactose residues from guar galactomannan to obtain modified guar galactomannan mimicking the functional properties of locust bean gum. The modified guar galactomannan blended with xanthan exhibited the rheological behaviour of elastic modulus (G′) greater than viscous modulus (G″) with a decrease in tan δ value similar to locust bean gum/xanthan blend. Also a twofold increase in the magnitude of elasticity compared to xanthan alone suggested the synergistic interaction with formation of three dimensional networks. The modified guar galactomannan with galactose content of 21% and M:G ratio 1:3.8, almost akin to locust bean gum, showed a better interaction with xanthan. Dynamic stress sweep study of modified guar galactomannan/xanthan blend with increased yield stress of 800 dynes/cm² also indicated the synergistic behaviour. Modified guar galactomannan also revealed the maximum synergistic interaction with xanthan at a mixing temperature of 60 °C than at 20 °C, 30 °C, 40 °C and 50 °C, respectively. Modification of guar galactomannan by pullulanase is an alternative route to produce galactose-depleted guar galactomannan with enhanced rheological functionalities on co-gelation with xanthan, as a cost effective replacement to locust bean gum.     

Rheological properties of whey protein isolate stabilized emulsions with pectin and guar gum

Dynamic oscillatory and steady-shear rheological tests were carried out to evaluate the rheological properties of whey protein isolate (WPI) stabilized emulsions with and without hydrocolloids (pectin and guar gum) at pH 7.0. Viscosity and also consistency index of emulsions increased with hydrocolloid concentration. At γ = 20 s⁻¹, the value of viscosity of the emulsion with 0.5% (w/v) pectin was about fivefold higher than that of the emulsion without pectin. Flow curves were analyzed using power law model through a fitting procedure. Flow behaviour index of all emulsions except for containing 0.5% (w/v) guar gum was approximately in the range of 0.9–1.0, which corresponds to near-Newtonian behaviour. The shear thinning behaviour of emulsions containing 0.5% (w/w) guar gum was confirmed by flow behaviour index, n, of 0.396. Both storage (G′) and loss modulus (G″) increased with an increase in frequency. Emulsions behaved like a liquid with G″ > G′ at lower frequencies; and like an elastic solid with G′ > G″ at higher frequencies. Effect of guar gum was more pronounced on dynamic properties. Phase angle values decreased from 89 to <10° with increasing frequency and indicated the viscoelasticity of WPI-stabilized emulsions with and without pectin/guar gum.     

Rheological properties of gluten-free bread formulations

In this study, the rheological properties of rice bread dough containing different gums with or without emulsifiers were determined. In addition, the quality of rice breads (volume, firmness and sensory analysis) was evaluated. Different gums (xanthan gum, guar gum, locust bean gum (LBG), hydroxyl propyl methyl cellulose (HPMC), pectin, xanthan–guar, and xanthan–LBG blend) and emulsifiers (Purawave^™ and DATEM) were used to find the best formulation for gluten-free breads. Rice dough and wheat dough containing no gum and emulsifier were used as control formulations. The rice dough containing different gums with or without emulsifiers at 25 °C showed shear-thinning behavior with a flow behavior index (n) ranging from 0.33–0.68 (except pectin containing samples) and consistency index (K) ranging from 2.75–61.7 Pa sⁿ. The highest elastic (G′) and loss (G″) module were obtained for rice dough samples containing xanthan gum, xanthan–guar and xanthan–LBG blend with DATEM. When Purawave^™ was used as an emulsifier, dough samples had relatively smaller consistency index and viscoelastic moduli values compared to DATEM. The viscoelastic parameters of rice dough were found to be related to bread firmness. Addition of DATEM improved bread quality in terms of specific volume and sensory values.     

Influence of selected hydrocolloids on triticale starch rheological properties

The aim of the study was to define the influence of selected nonstarch polysaccharides (guar gum, xanthan gum and arabic gum) on several rheological properties of triticale starch pastes/gels, at constant polysaccharide concentration (6.5 g/100 g). These included pasting characteristics, flow curves at 50 °C and mechanical spectra at 25 °C. It was found that the presence of a gum in a system modified the rheological properties of triticale starch gels/pastes, depending on the type and concentration of the gums. In the case of guar and xanthan gums, higher pasting viscosity was observed and the shear stress was increased compared with native starch. The presence of guar gum reduced the degree of thixotropy hysteresis, negative values for this being found for systems with xanthan in spite of their shear‐thinning behaviour. Systems containing arabic gum displayed lower values of pasting and flow viscosity. The type and concentration of gums added to the polysaccharide influenced the viscoelastic properties of the gels.     

Viscosity of solutions of xanthan/locust bean gum mixtures

Xanthan and locust bean gums are polysaccharides able to produce aqueous solutions with high viscosity and non‐Newtonian behaviour. When these solutions are mixed a dramatic increase on viscosity is observed, much greater than the combined viscosity of the separated polysaccharide solutions. In this work the influences of different variables on the viscosity of solutions of mixtures of xanthan/locust bean gum have been studied. Total polysaccharide concentration, xanthan and locust bean ratio on mixture and temperature at which the gum was dissolved (dissolution temperature) for both xanthan and locust bean gums have been considered. Under these different operational mixture conditions shear rate and time have also been considered to describe the rheological behaviour of the solutions studied. The high viscosity increase observed in these mixtures is due to the interaction between xanthan gum and locust bean gum molecules. This interaction takes place between the side chains of xanthan and the backbone of the locust bean gum. Both xanthan molecule conformation in solution – tertiary structure – and locust bean gum structure show great influence on the final viscosity of the solution mixtures. Xanthan conformation changes with temperature, going from ordered structures to disordered or chaotic ones. Locust bean gum composition changes with dissolution temperature, showing a dissolved galactose/mannose ratio reduction when temperature increases, ie the smooth regions – zones without galactose radicals – are predominantly dissolved. The highest viscosity was obtained for the solution mixture with a total polysaccharide concentration of 1.5 kg m⁻³ and a xanthan/locust ratio of 2:4 (w/w) and when xanthan gum and locust bean gum were dissolved at 40°C and 80°C, respectively. © 1999 Society of Chemical Industry     

Dynamic Rheology of Rice Starch‐Galactomannan Mixtures in the Aging Process

The effect of galactomananns (guar gum and locust bean gum) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) on the dynamic rheological properties of aqueous rice starch dispersions (5%, w/w) was investigated by small‐deformation oscillatory measurements during aging. Magnitudes of storage (G′) and loss (G′′) moduli measured at 4°C before aging increased with the increase in gum concentration in the range of 0.2–0.8%. G′ and G′′ values of rice starch‐locust bean gum (LBG) mixtures, in general, were higher than those of rice starch‐guar gum mixtures. G′ values of rice starch‐guar gum mixtures as a function of aging time (10 h) at 4°C increased rapidly at initial stage and then reached a plateau region at long aging times. However, G′ values of rice starch‐LBG mixtures increased steadily without showing a plateau region. Increasing the guar gum concentration resulted in an increase in plateau values. The rate constant (K) for structure development during aging was described by first‐order kinetics. K values in rice starch‐guar gum mixtures increased with the increase in guar gum concentration. G′ values of rice starch‐galactomannan mixtures after aging were greater than those before aging.     

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.     

Steady and dynamic shear rheology of sweet potato starch–xanthan gum mixtures

The effect of xanthan gum at different concentrations (0.2–0.6% w/w) on the rheological properties of sweet potato starch (SPS) pastes was evaluated under steady and dynamic shear conditions. The presence of xanthan resulted in an increase in the consistency index and vane yield stress of SPS. The effect of temperature on the apparent viscosity of SPS–xanthan mixtures is well described by the Arrhenius equation. Dynamic moduli (G′, G″, and η^*) values of the mixtures increased with an increase in xanthan concentration while the tan δ values decreased. The addition of xanthan appeared to contribute to the elastic properties of the weak network of the SPS pastes. The structure development rate constant (k) of gelation during ageing was strongly influenced by the presence of xanthan. This suggests that the phase separation process caused by the incompatibility phenomena between the amylose component in starch and xanthan can increase the elastic characteristics of the SPS–xanthan mixtures.     

Influence of guar gum addition on physicochemical,microbial, rheological and sensory properties of stirred yoghurt

This study investigated the effects of adding guar gum (0, 0.6 and 0.8 g/100 mL) on the physicochemical, microbial, rheological and sensory properties of stirred yoghurt. Incorporation of guar gum into the yoghurt significantly affected the pH and colour, but did not significantly influence the lactic acid bacteria counts. The magnitudes of apparent viscosity (η_a,100), consistency index (K), yield stress (σ_oc), storage modulus (G′) and loss modulus (G″) for yoghurt samples containing guar gum (0.6–0.8 g/100 mL) were significantly greater than those for the control (without guar gum), indicating that guar gum can improve the steady and dynamic shear rheological properties of yoghurt.     

Effects of Fat Replacers and Sweeteners on the Time-Dependent Rheological Characteristics and Emulsion Stability of Low-Calorie Pistachio Butter: A Response Surface Methodology

The effect of three fat replacers (xanthan gum, Reihan seed gum, and Balangu seed gum) and two sweeteners (sucrose and isomalt) on time-dependent rheological properties of low-calorie pistachio butter were analyzed using response surface methodology. The steady shear behavior of all samples was shear thinning (n = 0.156–0.6175), and power law model was fitted the upward and downward curves properly (R ² = 0.847–0.998). Balangu seed gum (0.01–0.04 wt.%), Reihan seed gum (0.01–0.023 wt.%), xanthan gum (0.06–0.1 wt.%), isomalt (0–1 wt.%), and sucrose (0.25–1 wt.%) were the levels investigated. A central composite design was used to develop models for the responses. The obtained experimental data were fitted to a second-order polynomial equation and also analyzed by appropriate statistical methods. In most cases, increasing the sweetener level led to a significant decrease in consistency coefficients. However, the effect on the flow behavior index was not significant. The effect of gum concentration on the rheological parameters was not significant (p ≤ 0.1), except for formulas prepared using Balangu seed gum. All formulas studied were stable on shelf.     

Intrinsic viscosity and viscoelastic properties of xanthan/guar mixtures in dilute solutions: Effect of salt concentration on the polymer interactions

An oscillating capillary rheometer was used to investigate the dynamic viscoelastic and intrinsic viscosity properties of deacetylated xanthan (0.025%), native xanthan (0.025%), guar gum (0.075%), and xanthan–guar mixtures in dilute solutions. Influence of ionic strength on xanthan conformation and interaction with guar gum was elaborated. As the salt concentration increased, a significant (P < 0.05) decrease in viscosity (η′) and elasticity (η″) values was observed for both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures. In water and 2 mM NaCl solution, the relative viscosity and η″ of both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures were much higher than of those calculated for mixtures assuming no interaction, whereas no pronounced increase was found for polysaccharide mixtures in 40 mM NaCl. The intrinsic viscosities of deacetylated xanthan–guar mixtures in water and 2 mM NaCl were higher, whereas the intrinsic viscosities of native xanthan–guar mixtures were lower than those calculated from the weight averages of the two individually, assuming no interaction. These results demonstrated that intermolecular interaction has occurred between xanthan and guar mixtures in water and 2 mM NaCl, but may not occur in 40 mM NaCl, and mutual incompatibility may occur. The results suggest that the degree of disordering of xanthan played a critical role in xanthan–guar interaction and may explain the differences in η′, η″, and intrinsic viscosity measurements between 2 and 40 mM NaCl.     

Oleogel production based on binary and ternary mixtures of sodium caseinate,xanthan gum,and guar gum: Optimization of hydrocolloids concentration and drying method

We report the optimization of oleogel formulation based on sodium caseinate (CN, 0–4 g/100 g), xanthan gum (XG, 0–1 g/100 g), guar gum (GG, 0–1 g/100 g), and drying method (freeze and oven drier) using response surface methodology to achieve the desired oil binding capacity, textural, and rheological attributes. All the selected responses were successfully fitted by a quadratic model with determination coefficient values higher than .95 with the exception of firmness values which was fitted by linear model. There were considerable increases in all the responses for the samples containing ternary mixtures of protein-gum (CN:XG:GG) as well as binary mixtures (CN:GG and CN:XG) compared to samples containing protein or gums alone due to the synergistic effect of CN and gums on formation of highly ordered and strong gel network. Regression modeling demonstrated that freeze drying method led to significantly greater structure recovery values than those of oven drying method. The best formulation was the freeze dried oleogel containing 4 g/100 g CN, 0.43 g/100 g XG, and 0.98 g/100 g GG. Results showed that fabrication of oleogels with at least 94.5 g/100 g sunflower oil and characteristics similar to industrial shortening is feasible.     

Viscoelastic characterization of fluid and gel like food emulsions stabilized with hydrocolloids

Food emulsions exhibit a great diversity of rheological characteristics; hydrocolloids are usually added to deal with creaming instability. Viscoelastic measurements provide information about the microstructure of the system. The objectives of this work were: a) to determine the viscoelastic behavior of two different low in fat oil-in-water food emulsions: a gel like and a fluid type emulsions stabilized with hydrocolloids (gellan gum and xanthan-guar mixtures respectively) b) to model and predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Low-in-fat oil-in-water emulsions (20 g/100 g) were prepared using sunflower oil and Tween 80 (1 wt.%). Fluid emulsions containing xanthan and guar gums were formulated using a synergistic ratio 7:3, with total hydrocolloid concentration ranging between 0.5 to 2 wt%. The aqueous phases contained NaCl (2 wt.%) and acetic acid (2 wt.%). The effect of hydrocolloids was studied using oscillatory measurements (G’ and G” vs. frequency) within the linear viscoelastic range previously determined by stress-sweeps. Time-Concentration Superposition principle was applied to find the master curves that describe the mechanical spectra of the viscoelastic materials. Superposition allows to obtain a wide spectrum of nearly ten decades of frequencies in emulsions containing xanthan–guar mixtures, whereas gellan gum systems did not show a significant frequency displacement. Viscoelastic behavior of the systems was satisfactorily modeled using Baumgaertel-Schausberger-Winter (BSW) equation. This empirical model was used to predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Validation of the predicted spectra was carried out through creep compliance data for emulsion-filled gels and steady-state flow curves for emulsions containing xanthan–guar mixtures.     

Influence of type,concentration and flow behaviour of hydrocolloid solutions on aroma perception

The effects of the addition of two hydrocolloids—locust bean (LBG) and xanthan gums—at two concentrations (0.2 and 0.5%, w/v) on the intensity of the aroma of limonene and of isopentyl acetate solutions was studied using the pairwise ranking test. Previously, the rheological behaviour of the studied gums was analysed, finding that while LBG solutions were slightly pseudoplastic at the lower concentration and more so at the higher one, the xanthan solutions were clearly pseudoplastic at both concentrations. Addition of 0.2% LBG did not alter the limonene aroma intensity perceived, but on adding 0.5% LBG, above the coil overlap concentration (c*), the decrease in aroma intensity was significant. Addition of xanthan gum at any concentration did not modify the limonene aroma intensity perceived by judges, which can be attributed to the low value of c* for solutions of this gum. No difference in isopentyl acetate aroma was found among samples.