Xanthan Gum Mixtures Research Articles

Influence of xanthan gum and locust bean gum upon flow and thixotropic behaviour of food emulsions containing modified starch

Low oil content mayonnaises are food emulsions which exhibit shear thinning and thixotropic behaviour. They include generally modified starch in their formulation. In this work we study the effect of substituting part of this starch with other natural gums, such as xanthan gum or locust bean gum, upon the consistency and stability of the emulsions in relation to stirring. The gels prior to final emulsification have also been analyzed. Steady flow curves of all systems are well described by the Carreau model. The emulsions containing the greatest percentage of gums presented significantly higher viscosity than the reference emulsion and the emulsions containing the synergistic mixtures of xanthan gum and locust bean gum. To analyze the time dependency, thixotropic loops were performed. Both up curves and down curves fitted the Herschel–Bulkley model. Analysis of the relative thixotropic areas calculated by integration, showed that starch substitution with gums led to an increase in emulsions thixotropy.

Formation and characterization of amphiphilic conjugates of whey protein isolate (WPI)/xanthan to improve surface activity

Proteins, polysaccharides and their blends, as examples of natural biopolymers, may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific compositions and conditions (protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing, processing steps) proteins and polysaccharides form water-soluble hybrids (complexes or conjugates), but not coacervates, with enhanced functional properties in comparison to the proteins and polysaccharides alone. Aqueous mixtures of WPI (4–10 wt%) and xanthan gum (>0.5 wt%) form clear aqueous systems exhibiting new physicochemical properties such as rheological behavior, surface properties, surface density of charge (zeta potential), surface hydrophobicity and diffusion behavior. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions were correlated to the functional properties (rheology, surface properties and surface hydrophobicity) of these adducts. Evidences for associative interactions between WPI and xanthan gum have been established by studying the rheological behavior, the surface hydrophobicity and the surface dynamic properties of the blends. The electrostatic and hydrophobic interactions form hybrids that can provide a synergistic effect on the emulsifying capabilities of the biopolymers and can increase the stability of emulsion droplets against coalescence and flocculation.

Study of emulsions stabilized with Phaseolus vulgaris or Phaseolus coccineus with the addition of Arabic gum, locust bean gum and xanthan gum

The properties of o/w emulsions stabilized with 1%w/v common bean ( Phaseolus vulgaris L.), V or scarlet runner bean ( P. coccineus L.), Coc extracted by isoelectric precipitation or ultrafiltration, at pH 7.0 and 5.5, with the addition of Arabic gum, locust bean gum, xanthan gum and a mixture of xanthan gum–locust bean gum (0.1 %w/v and 0.25 %w/v) are studied. The stability of emulsions was evaluated on the basis of oil droplet size, creaming, viscosity and protein adsorption measurements. The addition of Arabic gum, caused an increase in D[4,3] values and a decrease in the amount of protein adsorbed at the interface. The addition of locust bean gum in some emulsions reduced the amount of protein adsorbed. The addition of xanthan and to a less extend of the polysaccharide mixture, promoted a decrease in D[4,3]. So, emulsion stability was affected by the polysaccharide nature. Differences were also observed with respect to the protein nature, the method of its preparation and emulsion's pH. All polysaccharides enhanced the emulsions viscosity with xanthan and xanthan–locust bean gum exhibiting the higher values. V isolates and isoelectricaly precipitated isolates of both V, Coc showed higher viscosity values. The stability was enhanced by the increase of the viscosity of the continuous phase and the creation of a network, which prevents the oil droplets from coalescence.

Rheological properties of rice starch–xanthan gum mixtures

Rheological properties of rice starch–xanthan gum mixtures (5% w/w) at different xanthan gum concentrations (0%, 0.2%, 0.4%, 0.6%, and 0.8% w/w) were evaluated in steady and dynamic shear. The rice starch–xanthan gum mixtures at 25 °C showed high shear-thinning flow behavior ( n = 0.13–0.24), and consistency index ( K) and apparent viscosities ( η a,100) increased with the increase in xanthan gum concentration. In the temperature range of 25–70 °C, mixtures followed the Arrhenius temperature relationship. Activation energy (1.83–9.89 kJ/mol) decreased and storage ( G′) and loss ( G″) moduli increased with the increase in xanthan gum concentration. The dynamic ( η ∗) and steady shear ( η a) viscosities at several xanthan gum concentrations followed the Cox–Merz superposition rule with the application of shift factor ( α). Magnitudes of shift factor were in the range of 0.307–0.478. During aging at 4 °C for 10 h, the values of G′ were found to increase rapidly the early stage and attained the plateau region after a few hours. The increase in rate constant ( k) in gelation of rice starch–xanthan gum mixtures was a function of xanthan gum concentration.

Effects of guar gum and xanthan gum additions on physical and rheological properties of cationic tapioca starch

The gelatinization of cationic tapioca starch embedded in gum matrices was investigated by using a Rapid Visco-Analyzer (RVA), differential scanning calorimeter (DSC), scanning electron microscope (SEM), and rheometer. In addition, swelling power and solubility indices were measured. Xanthan and guar gum increased the RVA peak viscosity of cationic tapioca starch during pasting synergistically in different ways. Guar gum was more effective than xanthan gum in terms of increasing peak viscosity due to its ability to increase the swelling power and solubility index. Both xanthan gum and guar gum induced association between the gelatinized granules probably due to bridging. Association was much more extensive with xanthan. DSC studies showed that the presence of gums influenced the gelatinization characteristics of starch significantly by increasing the onset gelatinization temperature and decreasing the gelatinization enthalpy. Dynamic rheological measurement showed a strong interaction occurred in the cationic tapioca starch–xanthan gum mixture resulting in a decrease in the loss tangent (tan δ) as compared with guar gum addition or starch alone. The ionic interaction of gums and starch was found to play an important role in the gelatinization characteristics of the mixtures and also rheological properties of the pastes.

Rheology of dairy custard model systems: Influence of milk -fat and hydrocolloid type

The influence of milk-fat content and the addition of two types of hydrocolloid (λ-carrageenan and a mixture of λ-carrageenan and xanthan gum) on the pasting behaviour, the flow and the viscoelasticity of custard model systems with modified tapioca starch at different concentrations was studied. To evaluate the pasting behaviour, apparent viscosity and temperature data were recorded over time. Flow was measured by recording shear stress at shear rates from 1 to 200 s−1 and vice versa and viscoelasticity by performing the frequency sweeps from 0.01 to 1 Hz. Substitution of skim milk by whole milk increased apparent viscosity values during pasting. All the samples exhibited time dependence and pseudoplastic behaviour. Shear stress values increased when skim milk was substituted by whole milk, except for the custard system with 6% of starch. G′, G″ and η* values at 1 Hz resulted higher for whole milk systems although differences relatively decreased with starch concentration. The effect of hydrocolloid type was not significant (α=0.05) for all the parameters studied except for the n values.

Development of transverse ridges on rock glaciers: field measurements and laboratory experiments

AbstractVery high‐resolution photogrammetric and geodetic measurements about the deformation of transverse ridges on Murtèl, Muragl and Suvretta rock glaciers in the Swiss Alps are discussed. The ridges are advected downstreams with a speed that equals the overall speed of the creeping permafrost within the significance level of the applied techniques. Any process of ridge formation is, thus, overlain on the mass creep. In fact, measurements yield local speed maxima on top of the ridges that can be explained by differential movement due to ridge growth through bulging under compressive flow. This hypothesis is consistent with results from laboratory experiments that were performed on a model ramp employing mixtures of Xanthan Gum, sand and gravel. Indications were also found that overthrusting is involved in the development of transverse ridges on rock glaciers. Copyright © 2004 John Wiley & Sons, Ltd.

Colonic drug delivery of 5-fluorouracil: an in vitro evaluation

Compression coating has been found to be useful for colonic drug delivery. The aim of the present investigation was to design a formulation with a considerably reduced coat weight and gum concentration for colonic delivery of 5-fluorouracil for the treatment of colorectal cancer. Rapidly disintegrating core tablets containing 50 mg of 5-fluorouracil were prepared and compression coating with 175 mg of granules containing a mixture of xanthan gum (XG) and guar gum (GG) in varying proportions was done. With this coat weight, a highly retarded drug release was observed. After 24 h of dissolution the mean percent drug release from the compression coated XG:GG 20:20, 20:10 and 10:20 tablets were found to be around 18±1.23%, 20±1.54% and 30±1.77%, respectively. So, the coat weight was further reduced to 150 mg. It was observed that reduction of coat weight did not affect the initial drug release rate in simulated upper gastrointestinal tract (GIT) conditions. At the end of 24 h of dissolution the amount of drug released increased to 25±1.22%, 36.6±1.89% and 42.6±2.22%, respectively in XG:GG 20:20, 20:10 and 10:20 tablets. Studies of XG:GG (10:20) tablets in presence of colonic contents showed an increased cumulative percent drug release of 67.2±5.23% in presence of 2% cecal content and 80.34±3.89% in presence of 4% cecal content after 19 h of incubation.

Improved green properties of gelcast alumina through multiple synergistic interaction of polysaccharides

Abstract Carrageenans have been proposed for the aqueous gelcasting of ceramic and metallic powders because they form strong gels on cooling that allow fast consolidation and enhanced green strength. However, for additive contents above a threshold value, extensive plastic deformation occurs during fracture. Different gums can be combined with carrageenan to obtain the desired gel properties through synergistic interaction. In this work the combination of carrageenan with locust bean gum and with mixtures of locust bean gum and xanthan gum is investigated. The rheological behaviour of solutions (2 wt.%) of these three polysaccharides and their mixtures is studied at 60 °C, as well as the evolution of viscosity on cooling. The effect of mixtures of these gums on the rheological behaviour of deflocculated alumina slurries (50 vol.%, 80 wt.%) is also studied. The additions increase the viscosity of the suspensions and the deformability of the wet bodies. However, after drying, the green strength of the alumina pieces is enhanced and the plastic deformation during fracture is significantly reduced, thus improving machineability. The fracture strengths and Young's modulus values of alumina bars prepared with the three polysaccharides are around 4 MPa and 2 GPa, respectively. Relative densities are >55% of the theoretical value in the green state and ∼98% after sintering at 1500 °C/2 h.

Study of biopolymers as carriers for controlled release

An attempt was made to compare swelling and release behavior of two polysaccharides, xanthan gum (XG) and hydroxypropylmethyl cellulose (HPMC), taking into consideration their dissolution characteristics. This study was expected to provide information about the capability of these polymers to satisfy specific requirements in the design of controlled release systems. Tablets were prepared from the pure polymers as well as by using mixtures of XG and HPMC containing 1, 2, and 5% salicylic acid (SA) as a model drug. Swelling and dissolution experiments were run and the release in distilled water was recorded as a function of time. The results showed that XG and HPMC are very interesting matrices for the preparation of controlled release systems. Complete administration of SA in concentrations from 1 to 5% takes place within about 10 hr for XG, whereas approximately 5 days are necessary for the same result in the case of HPMC tablets. For both systems, nonFickian behavior was recorded with the diffusion exponent ranging from 0.67 to 0.78. Upon fitting the release data to the Peppas and Sahlin heuristic model, it was clear that, in general, erosion was the predominant factor for SA release from XG tablets, whereas the acid delivery from HPMC mainly proceeds via Fickian diffusion. These results seemed to be dependent on the water solubility of the released substance.

NMR water mobility in xanthan and locust bean gum mixtures: possible explanation of microbial response

Molecular and structural mobility of xanthan and locust bean gum mixtures (with and without mannitol) were studied in relation to microbial stability. Molecular mobility was measured by solid state 1H and 2H NMR and by 2H high resolution NMR while differential scanning calorimetry and dynamic mechanical analysis were used to investigate structural mobility. The NMR mobile signal was found to increase significantly with increasing moisture content and, at above 30% moisture content, the solid component disappeared with observed structural collapse. Cell survival decreased with moisture content increasing from 6 to 15% corresponding with an increasing mobile proton and deuterium signals (i.e. increased mobility). Presence of mannitol protected the cells from death at increasing moisture content and a relationship with a lower mobile 1H signal (as compared with the control) seems to be present. A strong mannitol–water interaction, leading to a decreased mobility, is suggested to play a role. No evidence of a glassy to rubbery transition was observed from DSC and DMA analyses, suggesting that structural relaxation did not play a significant role in NMR solid-liquid transition, i.e. NMR molecular mobility.

Viscosity, microstructure and phase behavior of aqueous mixtures of commercial milk protein products and xanthan gum

The behavior of commercial milk protein/xanthan mixtures was studied at neutral pH. Four milk protein ingredients; skim milk powder, milk protein concentrate, sodium caseinate and whey protein isolate were considered. For the xanthan concentrations used, up to 1wt%, the viscosity of the mixtures was dominated by the viscosity of xanthan. Mixtures of xanthan with skim milk powder or milk protein concentrate showed phase separation, as seen by confocal micrographs, and phase diagrams have been established for these two systems. No visible phase separation was observed in the case of mixtures of sodium caseinate or whey protein isolate systems. However, mixtures of sodium caseinate and xanthan, under certain conditions, showed formation of ‘thread-like’ xanthan-rich regions by confocal microscopy. We believe that the phase separation occurring in milk protein concentrate/xanthan or skim milk powder/xanthan mixtures was a result of depletion flocculation of casein micelles by the xanthan macromolecules, but thermodynamic incompatibility was likely to occur in sodium caseinate/xanthan mixtures.

Use of natural colorants in food gels. Influence of composition of gels on their colour and study of their stability during storage

Colour measurement was studied in gels prepared with four natural colorants (Annatto, Chlorophyllins, Cochineal and Curcumin), using gelatine or a mixture of xanthan gum and locust bean gum as gelling agent. A good correlation was found between sensory and instrumental evaluation, with the L ∗ and H ∗ parameters providing a good representation of the lightness and hue of the gels. Mathematical equations were developed, relating those parameters to the sugar and colorant concentrations. In all the gels it was found that L ∗ and H ∗ depended almost exclusively on the colorant concentration. The stability of the gelatine gels was studied during storage and was compared with that of commercial jellies. It was concluded that the natural colorants used (cochineal and curcumin) can replace the artificial ones found in commercial jellies.

Improved hypolipidemic effects of xanthan gum-galactomannan mixtures in rats.

This study describes the effects of mixtures of xanthan gum and galactomannan, guar gum, or locust bean gum, on the lipids in plasma and liver in non-diabetic and diabetic rats. Non-diabetic rats were fed cholesterol-free diets with 3% guar gum, locust bean gum, or xanthan gum (3G, 3L, and 3X), or a mixture of xanthan gum and guar gum or locust bean gum (1:2, w/w) (2G1X, 2L1X) for 2 weeks. Rats fed diets not containing these polysaccharides were used as controls. The total cholesterol in plasma and the triacylglycerol in liver were significantly lowered in rats fed the 2G1X diet. The 3G, 3X, 3L, and 2L1X diets showed no significant effect on the total cholesterol and triacylglycerol in plasma and liver. In the streptozotocin-induced (STZ) diabetic rats, the total cholesterol in plasma was lowered in rats fed the 3G, 3X or 2G1X diet for 4 weeks, and the 2G1X diet was more effective than the 3G and 3X diets. The triacylglycerol in plasma in STZ diabetic rats was also significantly lowered by the 2G1X diet. These results showed that a mixture of xanthan gum and guar gum has an improved hypolipidemic effect on non-diabetic and STZ diabetic rats. The effects of the 2G1X diet on the diabetic symptoms in STZ diabetic rats, suppression of food and water intakes, decrease in glucose in urine, and lowering of plasma glucose, were also observed.

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

FORMULATION AND QUALITY EVALUATION OF REDUCED SUGAR AND REDUCED CALORIE KAZANDIBI

ABSTRACT The production of kazandibi which is a milk pudding type of dessert for dietetic purposes was performed and the effects of various food additives on energy value, sensory and chemical components were investigated. A guar gum+xanthan gum (2.8+1.2) mixture besides rice milk and rice flour increased the textural quality whereas the artificial sweeteners aspartame+acesulfame K (0.25+0.25) together with small amounts of xylitol and fructose were effective in providing sufficient sweetness. Milk+cream aromas (1.5+0.3 and 1.5 + 0.5) had statistically significant (p < 0.05) effects in increasing flavor acceptability. The samples had higher protein contents (5%) and lower energy values (83kcal/100 g) than those of standard kazandibi and can be used both for diabetic and dietetic purposes.

Lightness and gloss of peach gels: effect of fruit and sugar content

Lightness and gloss were studied in peach gels prepared with different quantities of sugar and peach pulp, using a mixture of xanthan and locust bean gum as gelling agents. Colour was described in terms of the colour coordinates established by the Commission Internationale de l'Eclairage and gloss was determined as a percentage. The values of lightness determined optically (L*), when ranked, corresponded well with those determined by eye, but there was less similarity between the ranked values of gloss determined optically and by eye. There was a clear relationship between the sensory evaluation of lightness and gloss and the fruit and sugar content of these gels. Mathematical equations were developed to relate both L* and gloss values determined optically with fruit and sugar concentrations. It was found that fruit had a greater effect than sugar on the L* values and that gloss depended only on the sugar content. Finally, the gloss of gels prepared with different gelling agents were compared and it was found that lightness can affect the sensory evaluation of gloss.

Viscoelastic properties of [formula omitted] mixtures: comparison of guar gum with locust bean gum

The rheological behaviour of xanthan guar gum systems has been investigated and compared to that of xanthan locust bean gum mixtures using oscillatory shear and creep-recovery measurements. The total polysaccharide concentration was kept constant at 0.5% w/w, the xanthan galactomannan ratio ranged from 1 99 to 90 10 and three ionic strengths were studied. As for xanthan locust bean gum mixtures, strong synergistic phenomena were exhibited by xanthan guar gum systems. Clearly, the addition of xanthan gum even at a very low level to a guar gum solution induced a transition of the system from a macromolecular solution to a structured system displaying gel-like properties. The comparison between three guar gum samples with different molecular weights evidenced a strong effect of the molecular weight: the higher this parameter, the stronger the synergistic interaction. At a low xanthan galactomannan ratio ( < 10 90 ), xanthan guar gum mixtures, xanthan locust bean gum mixtures (with comparable galactomannan molecular weights) resulted in similar viscoelastic behaviour. In contrast, at a higher xanthan galactomannan ratio, a stronger synergism was exhibited with locust bean gum, as expected. The rheological properties were greatly influenced by the presence of electrolyte. In the case of xanthan guar gum systems, the storage ( G′) and the loss ( G″) moduli were increased when electrolyte was present, in contrast to xanthan locust bean gum mixtures which exhibited a reverse tendency. These results provide evidence that xanthan gum plays a major role in the rheological behaviour of the xanthan galactomannan systems even at a low concentration. Overall, similar results were found with xanthan guar or xanthan locust bean gum mixtures. However, differences in the mechanism may exist according to the mannose galactose ratio of the galactomannan and also to the xanthan galactomannan ratio and the ionic strength.

An investigation into the temperature dependence of the rheological synergy between xanthan gum and locust bean gum mixtures

The interaction between xanthan gum (XG) and locust bean gum (LBG) in water has been investigated using texture analysis, thermorheological analysis and high sensitivity differential scanning calorimetry. For the batches of XG and LBG used in the present study and at a total polymer concentration of 1% w/v, texture analysis indicated that the greatest synergy occurred at approximately 10% w/w XG, while the technique also allowed measurement of the increase in strength resulting from heating the mixes to 70 and 80°C and cooling to room temperature. Thermorheological studies showed a maximum in viscosity for the xanthan gum gels at approximately 45°C; this maximum became less pronounced as the concentration of XG decreased. High sensitivity differential scanning calorimetry indicated that XG undergoes two transitions at approximately 30 and 80°C on heating, but on cycling a single transition is seen at approximately 74°C. It was also noted that the transitions were diminished or were absent in the presence of LBG.

Combination effects of alpha-cyclodextrin and xanthan gum on rectal absorption and metabolism of morphine from hollow-type suppositories in rabbits.

Pharmacokinetics of morphine and its glucuronides in plasma were studied after rectal administration of hollow-type oleaginous suppositories containing kneading mixtures of morphine hydrochloride, alpha-cyclodextrin, and/or xanthan gum in rabbits. In combination with xanthan gum, alpha-cyclodextrin reduced the first-pass metabolism of morphine in the rectal mucosa and by the liver and improved the apparent rectal bioavailability of the opioid about 4 fold. In vitro permeation studies using an isolated rectal mucosal preparation of rabbits revealed that alpha-cyclodextrin increased the transepithelial conductance and facilitated the transport of morphine through the rectal mucosa. Furthermore, alpha-cyclodextrin facilitated its own mucosal permeation and reduced the glucuronidation of morphine during the passage through the rectal mucosa, probably through restricting the formation of a catalytic complex of morphine with glucuronyltransferases, rather than because of the enzyme saturation. The present data suggest that alpha-cyclodextrin in combination with xanthan gum is particularly effective in improving the rectal bioavailability of morphine from hollow-type suppositories.