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     

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.     

Influence of deacetylation on the rheological properties of xanthan-guar interactions in dilute aqueous solutions

ABSTRACT:  An oscillating capillary rheometer was used to investigate the effects of xanthan deacetylation on the viscoelastic properties and intrinsic viscosity of xanthan and guar mixtures in dilute aqueous solutions. Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xanthan did due to the destabilized helical structure and increased chain flexibility of the deacetylated xanthan. No gels were observed for all xanthan–guar mixtures. Native xanthan–guar mixtures exhibited a liquid-like behavior, whereas deacetylated xanthan–guar mixtures exhibited a gel-like behavior. The relative viscosity and elasticity of deacetylated xanthan–guar mixtures were much stronger than those for native xanthan–guar mixtures. The intrinsic viscosities of deacetylated xanthan–guar mixtures were higher than the calculated values assuming no interaction, whereas the intrinsic viscosities of native xanthan–guar mixtures were lower than the calculated values assuming no interaction, demonstrating that intermolecular binding occurred between the disordered segments of xanthan and guar gum in dilute aqueous solutions.     

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.     

A study on the effects of different gums on dielectric properties and quality of breads baked in infrared-microwave combination oven

In this study, the effects of different gums on dielectric properties of doughs and breads baked in infrared-microwave combination oven were investigated. In addition, the quality parameters of breads formulated with different gums baked in infrared-microwave combination oven were determined. The gums used were xanthan, guar, xanthan-guar blend and κ-carrageenan. The gums were added to the formulation at 0.5% concentration. The dielectric properties and quality parameters of breads baked in infrared-microwave combination oven were found to be dependent on gum type. κ-carrageenan resulted in undesirable final bread quality, while xanthan-guar blend addition improved bread quality (high specific volume and porosity, low hardness values). The dielectric properties of bread samples formulated with κ-carrageenan were found to be the highest among the other gum types.     

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.     

Experimental Analysis of Structural Change and Rheological Behavior of Macromolecular Solutions with Guar and Xanthan Gums in Crossflow Microfiltration Processing

The present paper reports on the structural change and rheological behavior of mixtures of macromolecular suspensions (guar and xanthan gums) in crossflow microfiltration processing. Mixtures in suspension of guar and xanthan gums at low concentrations (1,000 ppm) and different proportions were processed by microfiltration with membrane of nominal pore size of 0.4 μm. The rheological behavior of the mixtures was investigated in rotational viscometers at two different temperatures, 25 and 40 °C, at the beginning and at the end of each experiment. The shear stress (τ) in function of the shear rate (γ) was fitted and analyzed with the power-law model. All the mixtures showed flow behavior index values (n) lower than 1, characterizing non-Newtonian fluids (pseudoplastic). The samples of both mixtures and permeates were also analyzed by absorbency spectroscopy in infrared radiation. The absorbency analysis showed that there is good synergism between xanthan and guar gums without structure modifications or gel formation in the concentration process by microfiltration.     

Effects of food gums and pre-drying on fat content of fabricated fried chips

Deep-frying contributes to the unique taste and texture of fried products. However, they are low in nutritional value. Food industries actively trying to find ways to reduce the fat content while maintaining organoleptic properties of fried foods. In this work, effects of pre-drying and adding food gums on the moisture and fat contents of chips were evaluated. The chips were pre-dried for 60 and 90 min, and gellan gum, guar gum, methylcellulose and xanthan gum were added at the concentration of 0.25, 0.75, 1 and 2 % w/w. The xanthan gum was the most effective gum for fat reduction. The addition of 0.25 % w/w xanthan gum and at 90 min pre-drying reduced the fat content from 20 % (control) to 15 % w/w. The results also indicated that the reduction of moisture content after frying was not affected by the type of gums but the method of pre-drying.     

Exploring the applicability of tamarind gum for making gluten-free rice bread

The present study explored the applicability of tamarind gum in making gluten-free rice bread. Hydration properties of gums and pasting properties of rice flour with the gums were analyzed with Rapid ViscoAnalyzer. Batter properties and bread quality characteristics of rice bread containing gums were analyzed. Except for guar and xanthan gum, the final viscosity after hydration of other gums and the pasting properties of rice flour with the gums were similar. The batter properties and the quality of rice bread containing tamarind gum were equivalent or superior to those containing other gums. Cross-sections of rice bread showed that addition of tamarind gum and pectin resulted in a fine appearance, but pectin may not be preferred due to its lower pH causing unpleasant sour taste and smell of the rice bread containing the gum. Therefore, tamarind gum can be a useful gum for applying to make gluten-free rice bread.     

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.     

食品胶协同干热处理对马铃薯淀粉理化特性的影响

为了改善马铃薯淀粉加工特性,选用瓜尔胶、羧甲基纤维素钠和黄原胶3种食品胶分别与马铃薯淀粉复配后进行干热处理,研究食品胶协同干热处理对马铃薯淀粉糊化、老化和流变特性的影响。研究发现,中3种食品胶协同干热处理均能够降低糊化温度与糊化焓,并且均能增强淀粉体系稳定性,使其呈现出弹性流体性质,不仅如此还均能提高淀粉糊热稳定性以及耐剪切能力,此外均能增强淀粉凝胶的冻融稳定性。结果表明,3种食品胶协同干热处理均能起到改善马铃薯淀粉加工特性的作用,对其改善程度对比分析发现,黄原胶协同干热处理改善马铃薯淀粉特性效果最好。     

盐及非盐物质对常用低浓度食品胶溶液粘度影响的研究

对饮料生产中常用的食品胶－黄原胶、海藻酸钠、瓜尔胶和琼脂在低浓度水相体系中外加盐（阴、阳离子）、乙醇、蔗糖及柠檬酸对溶液粘度的影响作了探讨性研究,结果表明四种胶溶液（０．１０％黄原胶、０．３０％海藻酸钠、０．２５％瓜尔胶、０．１０％琼脂）中、瓜尔胶溶液对盐的耐受性最好,即大多数阴阳离子都不会对其粘度产生影响,而常用金属盐阳离子及Ｃｌ＾－、ＳＯ３＾２－对黄原胶溶液粘度的影响与阴阳离子对海藻酸钠和琼脂     

Effects of pectin and guar gum on creaming stability, microstructure and rheology of egg yolk plasma-stabilized emulsions

The influence of pectin and guar gum on the creaming stability, microstructure and rheological properties of 1.0% (w/v) egg yolk plasma (EYP)-stabilized 25.0% (v/v) soybean oil-in-water emulsions was studied at pH 7.0. Addition of pectin/guar gum decreased creaming percentage, and no creaming was detected in the presence of 0.5% (w/v) pectin/guar gum as a result of increasing viscosity. At the end of 10 h, creaming percentage decreased from 61 to 57% with the addition of 0.05% (w/v) guar gum and to 39% with the addition of 0.2% (w/v) guar gum. Microscopic observations represented the droplet aggregation arising from the presence of nonabsorbing biopolymers. At \mathop g^. \mathop \gamma \limits^{.}  = 10 s⁻¹, a tenfold increase in viscosity was observed in the presence of 0.5% (w/v) guar gum compared to the presence of 0.1% guar gum due to the thickening effect of polysaccharide. Increasing gum concentrations enhanced the viscosity and hence the consistency index. All emulsions, except for those containing 0.5% (w/v) guar gum, reflect the near-Newtonian behaviour with flow behaviour index, n, of 0.9–1.0. All emulsions exhibited a liquid-like behaviour at low frequencies (<7.0 Hz) where G″ values were higher than G′. Both G′ and G″ showed a frequency dependency and these two moduli crossed each other at higher frequencies (>7.0 Hz), G′ became greater than G″ and the system behaved like an elastic solid. Addition of pectin at all levels cause no significant change in G′ and G″ values, whereas addition of guar gum, especially at a concentration of 0.5% (w/v), significantly improved these values.     

Optimization of Baking of Rice Cakes in Infrared–Microwave Combination Oven by Response Surface Methodology

In this study, response surface methodology was used to design gluten-free cakes made from rice flour to be baked in infrared-microwave combination oven. Two types of cake formulations containing different types of gums were used in the experiments, which were xanthan gum and xanthan–guar gum blend. The independent variables were emulsifier content (0, 3, and 6% of flour weight), upper halogen lamp power (50, 60, and 70%), and baking time (7, 7.5, and 8 min). Specific volume, surface color change, firmness and weight loss of the cakes were determined for optimization. Cakes formulated with xanthan gum had better quality characteristics than cakes containing xanthan–guar gum blend. Cakes formulated with xanthan gum and 5.28% emulsifier and baked using 60% halogen lamp power for 7 min had the most acceptable quality.     

Rapid Visco-Analyzer (RVA) Pasting Profiles of Wheat,Corn, Waxy Corn,Tapioca and Amaranth Starches (A. hypochondriacus and A cruentus) in the Presence of Konjac Flour,Gellan, Guar,Xanthan and Locust Bean Gums

The Rapid Visco-Analyzer (RVA) 20min test was used to study the effects of different levels of konjac flour, guar, gellan, xanthan and locust bean gums on starch cooking properties. Wheat, corn, waxy corn, tapioca and A. hypochondriacus and A. cruentus starches were affected to different degrees by different levels of the gums. Peak viscosity increased at the higher gum concentrations, especially with locust bean gum at the 0.4 g level. The increase in viscosity was more pronounced with wheat and corn starches than with waxy corn and tapioca starches which consist mostly of highly branched amylopectin thus preventing close physical association between molecules. Amaranth starches showed much lower viscosity with all the gums than the other starches. Peak viscosity, time to reach the peak and maximum setback viscosity were affected by the gums. The increase in viscosity of starch/hydrocolloid systems is due to the release of amy-lose and low molecular weight amylopectin which promotes the formation of polymer complexes and significantly adds to the viscosity of the system.     

Optimization of gum combination for instant pudding based on creep and recovery parameters by mixture design approach

In the present study, gum combinations used in the pudding formulation were optimized by mixture design approach based on creep and recovery measurements. For this aim, four different gums (carrageenan, alginate, guar and xanthan gum) and their different combinations were used in the formulation. The creep-recovery properties of the pudding samples prepared with different gums or gum combinations were investigated. Burger model was satisfactorily applied for the determination of the creep-recovery characteristics of the samples. The use of the carrageenan in the pudding formulation caused a decrease in deformation of the samples. Gel strength value of the pudding samples was also calculated using the data. In order to optimize the gum combination based on the creep-recovery measurements, mixture design was carried out, and it was seen that established models satisfactorily predicted the viscoelastic parameters of the samples. During the optimization of the gum combination used in the pudding formulation, desirability function was used to optimize the ingredients simultaneously based on the requirements. The gum combination including 59.5 % carrageenan and 40.5 % guar gum or 52.7 % carrageenan, 33.8 % guar gum and 13.5 % xanthan gum was determined to be the optimum in terms of quality of the product.     

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     

Quantitative analysis of macro and micro-structure of gluten-free rice cakes containing different types of gums baked in different ovens

The effects of different gums on macro-structure of gluten-free rice cakes baked in conventional and infrared–microwave (IR–MW) combination ovens were investigated by using the images obtained by scanner and scanning electron microscopy in this study. The gum types used were xanthan, guar, locust bean, κ-carrageenan and xanthan–guar blend. Cake containing no gum was used as control. It was observed that both addition of different types of gums affected the pore area fraction and percent number of pores of the rice cakes. The highest pore area fraction was obtained in cakes containing xanthan and xanthan–guar blend. Cakes baked in IR–MW combination oven had higher porosity than those baked in conventional oven. Micro-structure of gluten-free rice cakes was also analyzed. According to these results, conventionally baked cakes showed more starch granule deformations. Both granular starch residues and deformed starch structure were observed together in cakes baked in IR–MW combination oven. All of the starch granules did not lose their identity and did not disintegrate completely.     

EFFECTS OF HYDROCOLLOIDS AND ASPARTAME ON SENSORY VISCOSITY AND SWEETNESS OF LOW CALORIE PEACH NECTARS

Effects were studied of interactions between each of three hydrocolloids-xanthan gum, guar gum and methylcellulose- and aspartame on sweetness intensity and sensory viscosity of low-calorie peach nectars (60% fruit purée with no sucrose added). The flows of the nectars were characterized as near Newtonian without hydrocolloids, as Bingham plastic at lower hydrocolloids concentrations and as pseudoplastic at higher concentrations (Ostwald flow for guar and methylcellulose, and Herschel-Bulkley for xanthan). Hydrocolloids concentrations were selected to cover viscosity range of commercial whole nectars: 0.10 and 0.20% xanthan or guar, and 0.15 and 0.30% methylcellulose. Aspartame concentrations tested were derived from the calculation of equisweet concentration as referred to a control nectar sample with sucrose (14°Brix) and of the upper and lower limen value: 0.216, 0.360 (equisweet), 0.502, and 0.644 g/L. Addition of either guar or methylcellulose did not alter the perceived sweetness in aspartame-sweetened peach nectars. Xanthan addition, even at 0.10%, significantly lowered sweetness of samples sweetened with the highest aspartame concentration (0.644 g/L). Addition of aspartame did not modify the perceived viscosity in samples thickened with either xanthan or guar gums. At all methylcellulose concentrations tested, samples with the lowest aspartame concentration (0.216 g/L) were perceived as less viscous.     

Effect of Anionic Gums on the Texture of Pickled Frankfurters

The addition of the anionic gums, xanthan and carrageenan, stabilized the texture of frankfurter emulsions against acid deterioration at 37°C in vinegar pickle. The proteins collagen, casein, and gluten, and the gums guar, arabic, and locust bean had no effect. The cationic gum, chitosan, formed an acid-stable gel but the gel would not hold the emulsion. The process of acid deterioration had an initial period of firming of the gel texture. Shear (rupture) and elasticity did not show a corresponding initial increase. Subsequent deteriorative changes were less in the emulsions with xanthan gum than in any of the other emulsions. The gum gel is formed at the expense of the protein-fat structure, probably through a gum-protein interaction.