Influence of Deacetylation on the Rheological Properties of Xanthan?Guar Interactions in Dilute Aqueous Solutions (original) (raw)
Related papers
Food Research International, 2006
Dynamic viscoelastic and intrinsic viscosity properties of xanthan, guar, and xanthan-guar blends in dilute aqueous solutions were investigated by using an oscillating capillary rheometer. Influence of mixing temperature on xanthan conformation and interaction with guar is discussed. Synergistic interaction occurred at mixing temperatures of 25 and 80°C, but a stronger synergistic interaction was observed at mixing temperature 80°C. The viscous component for all gum solutions was greater than that of the elastic component, which indicated a liquid-like behavior in the dilute regime for the polysaccharide solutions. For both mixing temperatures, the relative viscosities and elasticities of xanthan and guar blends were higher than the relative viscosities and elasticities calculated for blends assuming no interaction. The intrinsic viscosities of xanthan and xanthan-guar blends were higher at 80°C than at 25°C. The intrinsic viscosities of xanthan and guar blends were lower than those calculated from the weight averages of the two, and significantly decreased as the xanthan fraction decreased, indicating that xanthan was crucial in controlling the blend viscosity, and that the molecular binding occurred between xanthan and guar.
Food Research International, 2007
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 (g 0 ) and elasticity (g 00 ) 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 g 00 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 g 0 , g 00 , and intrinsic viscosity measurements between 2 and 40 mM NaCl.
Carbohydrate polymers, 2018
The influence of concentration on the shear and extensional rheology properties of aqueous solutions of xanthan and guar gums was studied in this work. Shear rheology involved small amplitude oscillatory shear (SAOS), flow curves and transient flow, while the extensional rheology was analyzed using hyperbolic contraction flow. In addition, the mechanical properties during solutions manufacture were monitored in situ through the evolution of torque with processing time by mixing rheometry. The results showed that the hydrocolloids exert a great influence on the process rheokinetics and on the resulting rheological response. SAOS tests showed that the xanthan gum solutions behaved as weak gels, whereas guar gum solutions suggest the presence of entanglement and the formation of a viscoelastic, gel-like structure. All the systems exhibited shear-thinning behaviour. Guar gum solutions obeyed the Cox-Merz rule, with some divergence at high rates for the more concentrated solutions, while...
Role of conformation and acetylation of xanthan on xanthan-guar interaction
Carbohydrate Polymers, 1992
The synergistic effect obtained by mixing xanthan and guar solutions were examined by low shear viscosity measurements in relation to the temperature. Native and deacetylated xanthan samples were used in mixtures in which the total polymer concentrations were 1 g/litre and 0.5 g/litre. Gelation was observed for temperatures lower than 15 °C for the native xanthan-guar system (weight ratio 1/1) in 10 -2 M NaC1 and at 22-24°C for the same system in water; in this last case, it is known that the xanthan is in the disordered conformation. For a mixture of deacetylated xanthan-guar, gelation was observed at a temperature below 26°C in water. The results confirm that there is a stronger interaction between deacetylated xanthan and guar than native xanthan and guar because of enhanced xanthan-guar gum backbone association in the former case.
Synergistic gelation of xanthan gum with locust bean gum: A rheological investigation
1997
Many industrial products often include in their formulation more than one polysaccharide to achieve the desired properties during and after processing. Many such mixed systems behave as would be expected from the known properties of the individual polymers. In others, however, their properties are superior to those of either component alone, or may be qualitatively different. In many polysaccharide systems, the combination of a gelling polymer with a nongelling one gives rise to strong synergistic effects, as a consequence of interaction among different chain polymers and formation of mixed junction zones.
Viscosity of guar gum and xanthan/guar gum mixture solutions
Journal of the Science of Food and Agriculture, 2000
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 À3), 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 À3 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.
Rheological studies on the interaction of xanthan and locust bean gum in aqueous dispersions
1985
In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.
Food Hydrocolloids, 2014
A particulate form of xanthan gum was prepared by extrusion cooking. The temperature dependence of the viscosity of this form shows similarities to starch with an increase in viscosity to a maximum with increasing temperature as a result of the swelling of the particles. The rheology and mixing behaviour with water of the particulate and conventional molecular forms of xanthan were compared with a modified starch. The particulate xanthan products mixed rapidly with water in a similar way to ungelatinised starch, whereas conventional molecular xanthan systems mixed poorly. Using an experienced sensory panel, model tomato products thickened with the three systems were compared at equal shear viscosities. The panel could not discriminate between the tomato flavour of the three products, but found that the xanthan products were perceived as being significantly thicker. These observations were consistent with previous work. Salt perception for both xanthan products was poorer than for the starch thickened systems. A hypothesis to explain why xanthan does not fit into the previously postulated link between mixing and perception is presented.
Rheology and microstructure of galactomannan–xanthan gum systems at different pH values
Journal of Food Process Engineering, 2020
pH is a significant parameter influencing the performance of biopolymer solution fluids. The rheological properties, structural strength, viscoelastic properties of xanthan gum-galactomannan solutions were largely depended on the pH values. The present research aims to determine the effect of pH on galactomannan-xanthan gum blends. For the sample solutions, an apparent viscosity-increasing effect was explicitly observed over the pH range from 2.0 to 6.0, and the consistency coefficient values gradually decreased at pH 2.0. The G 0 values of the samples which contained the same ratio of hydrocolloid with different pH values were 1.03, 3.43, 13.98 Pa and G 00 values were 1.15, 1.29, and 2.99 Pa, respectively. Optimization results represented that the best galactomannan type is tara gum prepared at pH 2.0, tara gum and LBG at pH 4.0. For the solutions prepared at pH 6.0, the optimum results were obtained with the LBG compared with the three studied galactomannan-xanthan gum solution. By optical microscopy, the particle morphology of solutions was different from each other at optimum concentrations and pH. These findings indicate that conditions for providing certain viscoelastic attributes of xanthan-galactomannan dispersions for the purpose of particular applications by careful control of pH. Practical Applications Xanthan gum and galactomannan combinations found many applications in various food products such as ready-to-use dessert soups and salad dressing. There was a research gap to find the optimum xanthan gum and galactomannan combinations along with different pH. The present study investigated the effect of pH on steady and dynamic rheological properties of xanthan gum-galactomannan mixtures. Optimization study was conducted and compared with different pH. Obtained results of current study highlighted the importance of determining the pH for food formulation because they can be used to alter the rheology of food matrices and to get a deeper knowledge on the effects of the pH on the morphology of the system. The present study makes several noteworthy contributions to the rheological characteristics of galactomannan containing food products. These findings indicate that conditions for providing certain viscoelastic attributes of xanthan-galactomannan dispersions for the purpose of particular applications by careful control of pH.