Xanthan Gum Dispersions Research Articles

Yogurt Enriched with Mango Peel Extracts (Mangifera indica) in Chitosan–Xanthan Gum Dispersions: Physicochemical, Rheological, Stability, and Antioxidant Activity

Different strategies have been developed to incorporate bioactive compounds into food products to improve their biological activity against degradation effects. The aim of this study was to develop natural yogurt enriched with mango (Mangifera indica) peel extracts (MPEs) in chitosan–xanthan gum dispersions and to evaluate their physicochemical, rheological, and antioxidant activity. A hydroethanolic extract of mango peel was obtained, with a yield of 33.24 ± 1.27%, a total content of phenolic compounds of 305.04 ± 10.70 mg GAE/g, and an antioxidant activity of 1470.41 ± 59.75 μMol Trolox/g. The encapsulation of the extracts was achieved using a chitosan–xanthan gum dispersion, resulting in the rheological characteristic of a strong gel. The incorporation of dispersions into yogurt did not modify the physicochemical properties and increased their bioactive properties. The rheological properties show samples with double yield points and a decrease in viscoelastic parameters. These results show dispersions as a strategy to incorporate bioactive compounds into dairy products, preserve the physicochemical and rheological properties of yogurt, and improve their biological activities (such as antioxidant activity) and activities related to the compounds found in the MPE.

A simple portable magnetic resonance technique for characterizing circular couette flow of non-Newtonian fluids

In this work, we expand on past portable magnetic resonance flow methods and propose a novel method for characterizing circular (laminar) Couette flow of non-Newtonian fluids. Symmetry of the flow system combined with a constant magnetic field gradient leads to phase interference, affecting the signal magnitude, and net phase cancellation when averaging across the excited slice, preventing the use of phase-sensitive methods. Therefore, we utilize the dependence of signal magnitude at variable echo times and shear rates to characterize rheological properties. Theoretical equations governing the velocity distributions of fluids that obey a simple power-law model are used to obtain integral expressions for signal magnitude. Integral expressions can be simplified by approximating a thin excited slice or complete excitation of the Couette cell depending on experimental parameters. With simple data acquisition and analysis procedures employed, our measurements of the flow behavior indices of non-Newtonian xanthan gum dispersions are in close agreement with conventional rheological magnetic resonance measurements.

Optimization of high-pressure-assisted xanthan gum dispersions for the maximization of rheological moduli: Application of time-pressure/ temperature superposition principle

The influence of high-pressure (HP) treatment (300–600 MPa) on the rheological behavior of xanthan gum (XG) dispersions was studied at ambient temperature. The pressure-treated samples were thereafter isothermally heated in situ in a rheometer to include the thermal effect on the oscillatory rheology. The main objective of this work was to study the influence of three independent variables, namely concentration (0.75, 1 and 1.25%), pressure (0.1, 300 and 600 MPa), and temperature (40, 55 and 70 °C) on the maximization of the oscillatory rheological moduli (G′, G″ and η*) of xanthan gum using central composite design (CCD) method. The developed quadratic regression model indicated that all the linear, two quadratics (concentration and temperature), and two interactions (concentration-pressure and concentration-temperature) terms were significant (P < 0.05) for oscillatory moduli (R2 = 0.99) and insignificant lack-of-fit. The mechanical rigidity produced by the pressure was higher than the thermally treated xanthan, which needs further in-depth structural analysis to confirm the pressure-assisted order-disorder transition. Both the time-pressure and time-temperature superposition principles were fitted well for the HP-treated xanthan dispersions.

Rheological Properties of Aqueous Dispersions of Xanthan Gum Containing Different Chloride Salts Are Impacted by both Sizes and Net Electric Charges of the Cations

Xanthan gum (XG) is one of the most effective thickener agents used worldwide. In foods products, one of the factors affecting its physical properties is the ionic strength of the medium. Though it is well known that XG rheological properties in aqueous media depend on both type and concentration of electrolytes, correlations between such dispersion properties and molecular aspects of dispersed XG chains are still to be more deeply studied. Thus, in the present study, aqueous XG dispersions [200 mg⋅(100 mL)−1] added of Na, K, Mg or Ca chlorides (ionic strength 50 mM or 100 mM) were rheologically characterized, and the corresponding results were explained based on different physicochemical analyses. Comparing to the control (unsalted XG dispersion), KCl and CaCl2 tended to produce a more drastic decrease of apparent viscosities of XG dispersions than NaCl and MgCl2. In dynamic-oscillatory assays, the predominance of elastic character over viscous character was more evident for XG dispersions containing KCl and CaCl2, in particular at frequencies > 0.1 Hz. XG dispersions containing KCl or CaCl2 also presented smaller pH and |ζ-potentials| values, as well as greater densities and average hydrodynamic diameters of dispersed XG chains, when compared to respective counterparts containing NaCl or MgCl2. As the decreasing order of the cations radii is K+ > Ca2+ ≈ Na+ > Mg2+, our results allowed deducing that not only the net electric charges of the cations, but also their sizes, should be considered when analyzing the effect of chloride salts on rheological properties of XG aqueous dispersions, according to the desired for this hydrocolloid (weak thickener, strong thickener or pro-gelling agent).

Rheological Characterization of Bentonite Dispersions with Xanthan for Oil Well Drilling Fluids

Shear tests using a coaxial cylinders viscometer were performed in order to determine the rheological and thixotropic properties of xanthan gum dispersions with sodium bentonite in the presence of high salt concentrations of sodium and calcium chlorides. The dispersions rheology with different temperatures and concentrations of NaCl, CaCl2 and xanthan gum were prepared by fixing the bentonite concentration of 1%. The dispersions showed a good fit to power law model through linear regressions with the lowest coefficient of determination value of 0,98. A screening was made initially to decide which independent variables potentially affect the rheological and thixotropic parameters. The independent variables were temperature, the xanthan gum and sodium and calcium chlorides concentrations. Then a full factorial design in duplicate with the remaining variables on the same tracks was performed. The results eliminated calcium chloride as an independent variable and revealed a strong dependence of the rheological and thixotropic parameters with temperature and xanthan gum and NaCl concentrations.

Rheology of dispersions of xanthan gum, locust bean gum and mixed biopolymer gel with silicon dioxide nanoparticles.

Mixed xanthan gum (XG) and locust bean gum (LBG) biopolymers form thermally reversible gels of interest in tissue engineering and drug delivery. 1% solutions of XG, LBG and 1:1 ratio XG/LBG mixed gels (LX) containing silicon dioxide (SiO2) nanoparticles were rheologically characterized with respect to nanoparticle concentration and temperature. 10% nanoparticles in XG created larger domains of associated polymer, resulting in enhanced viscosity and viscoelastic moduli. In LBG with 10% particles, transient viscosity and a gel-sol transition occurred due to particle bridging and aggregation. In the LX gel, 10% SiO2 particles caused an increase in elasticity. When ramping temperature from 25°C to 85°C, the complex modulus for all solutions containing 10% SiO2 was relatively constant, indicating that nanoparticles counteracted the effect of temperature on the material properties. Understanding the influence of nanoparticle loading on material properties is necessary for biopolymer material development where property prediction and control are critical.

Yield stress components of waxy corn starch–xanthan mixtures: Effect of xanthan concentration and different starches

Yield stress of 6% (w/w) waxy maize (WXM), cross-linked waxy maize (CLWM), and cold water swelling (CWS) starches in xanthan gum dispersions: 0%, 0.35%, 0.50%, 0.70%, and 1.0% was measured with the vane method at an apparent shear rate of 0.05 s −1. The intrinsic viscosity of the xanthan gum was determined to be: 112.3 dL/g in distilled water at 25 °C. Values of the static ( σ 0s) and dynamic ( σ 0d) yield stress of each dispersion were measured before and after breaking down its structure under continuous shear, respectively. The WXM and CWS starches exhibited synergistic behavior, whereas the CLWM starch showed antagonistic effect with xanthan gum. The difference ( σ 0s − σ 0d) was the stress required to break the inter-particle bonding ( σ b). The contributions of the viscous ( σ v) and network ( σ n) components were estimated from an energy balance model. In general, values of σ b of the starch–xanthan gum dispersions decreased and those of σ n increased with increase in xanthan gum concentration.

Chemical and rheological properties of an extracellular polysaccharide produced by the cyanobacteriumAnabaena sp. ATCC 33047

The cyanobacterium (blue-green alga) Anabaena sp. ATCC 33047 produces an exopolysaccharide (EPS) during the stationary growth phase in batch culture. Chemical analysis of EPS revealed a heteropolysaccharidic nature, with xylose, glucose, galactose, and mannose the main neutral sugars found. The infrared (IR) spectrum of EPS showed absorption bands of carboxylate groups. The average molecular mass of the polymer was 1.35 MDa. Aqueous dispersions at EPS concentrations ranging from 0.2% to 0.6% (w/w) showed marked shear-thinning properties (power-law behavior). Linear dynamic viscoelastic properties showed that the elastic component was always higher than the viscous component. Viscous and viscoelastic properties demonstrated the absence of conformational changes within the concentration range studied. Stress-growth experiments revealed that 0.4% and 0.6% (w/w) EPS dispersions showed thixotropic properties. A detailed comparison of the linear dynamic viscoelasticity, transient flow, and decreasing shear rate flow curve properties was made for 0.4% (w/w) dispersions of xanthan gum (XG), Alkemir 110 (AG), and EPS. Viscoelastic spectra demonstrated that the EPS dispersion turned out to be more "fluidlike" than the AG and XG dispersions. The flow indexes indicated that the EPS dispersion was less shear-sensitive than that of XG, showing essentially the same viscosity, that is, >50 s(-1). The fact that viscosities of EPS and AG dispersions were not substantially different within the shear-rate range covered must be emphasized, in relation to EPS potential applications. The rheological behavior of EPS dispersions indicates the formation of an intermediate structure between a random-coil polysaccharide and a weak gel.

Chemical and rheological properties of an extracellular polysaccharide produced by the cyanobacterium Anabaena sp. ATCC 33047

The cyanobacterium (blue-green alga) Anabaena sp. ATCC 33047 produces an exopolysaccharide (EPS) during the stationary growth phase in batch culture. Chemical analysis of EPS revealed a heteropolysaccharidic nature, with xylose, glucose, galactose, and mannose the main neutral sugars found. The infrared (IR) spectrum of EPS showed absorption bands of carboxylate groups. The average molecular mass of the polymer was 1.35 MDa. Aqueous dispersions at EPS concentrations ranging from 0.2% to 0.6% (w/w) showed marked shear-thinning properties (power-law behavior). Linear dynamic viscoelastic properties showed that the elastic component was always higher than the viscous component. Viscous and viscoelastic properties demonstrated the absence of conformational changes within the concentration range studied. Stress-growth experiments revealed that 0.4% and 0.6% (w/w) EPS dispersions showed thixotropic properties. A detailed comparison of the linear dynamic viscoelasticity, transient flow, and decreasing shear rate flow curve properties was made for 0.4% (w/w) dispersions of xanthan gum (XG), Alkemir 110 (AG), and EPS. Viscoelastic spectra demonstrated that the EPS dispersion turned out to be more “fluidlike” than the AG and XG dispersions. The flow indexes indicated that the EPS dispersion was less shear-sensitive than that of XG, showing essentially the same viscosity, that is, >50 s−1. The fact that viscosities of EPS and AG dispersions were not substantially different within the shear-rate range covered must be emphasized, in relation to EPS potential applications. The rheological behavior of EPS dispersions indicates the formation of an intermediate structure between a random-coil polysaccharide and a weak gel. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 67: 283–290, 2000.

Chemical and physical properties of yellow mustard ( Sinapis alba L.) mucilage

The yield of crude mucilage (CM) obtained from yellow mustard ( Sinapis alba, L.) was 5% of the total seed weight. CM was separated into a water-soluble fraction (WS, 55·6%) and a water-insoluble fraction (WI, 38·8%). Proximate analysis of CM and its fractions revealed carbohydrates as the major component (80–94%) with ash (1·7–15·0%) and protein (2·2–4·4%) as minor constituents. Glucose (22–35%) was the major monosaccharide present followed by galactose (11–15%), mannose (6·0–6·4%), rhamnose (1·6–4·0%), arabinose (2·8–3·2%) and xylose (1·8–2·0%). All mucilage fractions exhibited interfacial activity and shear thinning behaviour typical of xanthan gum dispersions. Of the mucilage fractions studied, the WS fraction was least affected by pH, temperature and solutes (NaCl, sucrose).

High shear rate flow behavior of xanthan gum dispersions

The high shear rate flow behavior of aqueous xanthan gum dispersions of 0.05, 0.10, 0.25, 0.50 and 1.0% w/w concentration, was determined at 5, 15, 25 and 35°C by capillary rheometry. Viscosity declined with increasing shear rates and approached a constant infinite shear viscosity, over a shear rate range of 1000–250 000/s. This viscosity decline was modeled using non-linear regression to relate apparent viscosity to shear stress and infinite shear viscosity. Arrhenius and Huggins models were then used to describe the variation of infinite shear viscosity with temperature and concentration respectively. Multiple regression was used to express the logarithm of infinite shear viscosity as a function of the logarithm of concentration and reciprocal of the absolute temperature. Examination of the data revealed that xanthan solution viscosities at high rates of shear were less dependent on gum concentration than on solvent viscosity.

Injectivity Improvement of Xanthan Gums by Enzymes: Process Design and Performance Evaluation

Summary. Injectability and filterability of xanthan gum dispersions, especially in hard brines, can be considerably improved by successive use of cellulose and alkaline protease enzyme treatments. A thorough optimization of the different parameters controlling enzymatic activity has led to an original clarification process. Improvements observed in flow behavior of treated xanthan gum solutions through reservoir rocks is the result of almost complete elimination of both insoluble bacterial cells and microgels. Introduction Aqueous xanthan gum dispersions prepared either by dilution of raw fermentation broths or by dissolution of xanthan powders still contain insoluble particles and microgels. Different treatments, including, diatomaceous earth filtration or the action of protease enzynes, have been proposed to improve the limpidity and thereby the injectability of diluted xanthan gum solutions. These clarification procedures were shown to be unable to reduce the plugging, capacity of shear-deformable microgets at a very short distance from the injection well. The result is a poor sweeping efficiency of reservoir rocks by imperfectly clarified polysaccharide solutions. Plugging by microgels can be reduced by subjecting xanthan gum dispersions to the action of polysaccharase enzymes. This treatment is considered satisfactory it applied to xanthan powder dispersions containing, a limited amount of residual dead bacterial cells. The higher biomass content of raw xanthan broths renders the cellulose treatment less efficient. A synergetic effect in elimination of both microgels and insoluble particles is obtained by application of polysaccharase and protease treatments either successively or simultaneously. This paper describes the process resulting, from previous studies and enables these treatments to be performed previous studies and enables these treatments to be performed either in the field or at the factory site at the end of the biopolymer fermentation process. Performance evaluation of the enzymatic treatments on xanthan broths and Powders, respectively, was carried out by injection of the resultant solutions at high and low flow rates through both calibrated filters and natural cores. Fundamentals of Enzymatic Treatments Recent publications have shown that it is easy to hydrolyze the main chain of the xanthan molecule by polysaccharase enzymes, commonly called celluloses. As a polysaccharase enzymes, commonly called celluloses. As a consequence, glucose or reducing sugars are released in solution, and both molecular weight and viscosity diminish. Nevertheless. hydrolysis through cellulases occurs only if the xanthan molecule is in an unordered conformation. This conformation prevails at room temperature in low-salinity brines and at higher temperatures if salinity is high. Similar treatments applied to raw xanthan gum dispersions in brines with an overall salinity greater than 5 × 10 mol/L and at temperatures lower than 65 degrees C [149 degrees F] were shown to contribute to the clarification of these solutions and to the progressive microgel elimination. With this treatment. the main xanthan chain remains unaltered, the viscosity of the polymer solution is unchanged, and the xanthan gum' s injectability is improved. Treatments by cellulases performed on xanthan gum dispersions in brines exhibiting greater hardness were nevertheless found to be unsatisfactory. A synergetic treatment was therefore developed consisting of two successive enzymatic treatments, one at pH 4.5 and 50 degrees C [122 degree F] with a cellulase and the second at pH 9 and 50 degrees C [122 degrees F] with an alkaline protease. This process allows almost total microgel elimination and improvement in the filterability of the resultant xanthan gum solutions. Experimental Polymers. The main characteristics of the xanthan gums Polymers. The main characteristics of the xanthan gums tested throughout this study are listed in Table 1. Both fermentation broths and powdered-form products of various origins were used. Enzymatic treatments were applied to xanthan gum dispersions with concentrations ranging from 1 to 9 wt%. For laboratory tests. no special equipment was used to disperse the polymer; gentle stirring in the hydrolysis unit for about 2 hours before enzymes were added was found to be sufficient. For pilot tests (1 m [264 gal]), a special dispersion device was pilot tests (1 m [264 gal]), a special dispersion device was used for the powder to ensure complete solubilization of the polymer in less than 2 hours. Enzymes. Two types of enzymatic preparations that are commercially available in powder form were used throughout this study: JPT P. 835

LITERATURE ABSTRACTS

LITERATURE ABSTRACTS

Concentration and Temperature Dependence of Flow Behavior of Xanthan Gum Dispersions

ABSTRACTApparent viscosities of xanthan gum dispersions over shear rates of 0.5–3000s−1 were studied at concentrations of 0.05–1.00% (w/w) and temperatures of 5–45°C. All dispersions were shear rate thinning non‐Newtonian fluids described accurately by the power‐law model. The logarithm of viscosity varied with the logarithm of concentration and the reciprocal of absolute temperature. A combined model was derived to describe the variation of viscosity with shear rate, concentration and temperature for aqueous dispersions of xanthan gum.

Elimination of Xanthan Microgels by New Enzymatic Treatments

Abstract Polysaccharase and particularly combined polysac-charase/protease treatments offer new alternatives for clarifying aqueous xanthan gum dispersions. Each enzyme has its specific action—the proteases on the insoluble residual bacterial cells, and the polysaccharases primarily on the microgels. Preliminary tests of these enzymatic treatments for scheduled field applications show promising improvements in filterability, especially for solutions prepared from xanthan powders.