Chapter

Xanthan Gum

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  • IFF Paris, France
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Abstract

Xanthan gum is a high-molecular-weight polysaccharide secreted by the microorganism Xanthomonas campestris and produced commercially in a batch fermentation process. It hydrates in cold water to give a viscous solution with pseudoplastic flow behaviour. This gives excellent suspension and cling at low shear and excellent mouthfeel and pouring properties at high shear. The xanthan gum molecule has a cellulosic backbone with side chains that wrap around the backbone protecting it and conferring excellent stability across a wide pH range and tolerance of high salt concentrations and ingredients such as glycerol and alcohol. The rigid backbone helps to maintain viscosity during heating. Xanthan gum shows synergistic thickening with guar gum and forms very elastic cohesive gels with locust bean gum and konjac mannan. Non-food uses include oil field, personal care, pharmaceutical and home care products. Typical food applications include sauces and dressings, baked goods, beverages, desserts and ice creams.

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... In the following section the characteristics of these hydrocolloids are described in more detail. [19,20]. ...
... The xanthan gum molecule consists of D-glucose, D-mannose and D-glucuronic acid in a molar ratio of 2.8:2:2 [20]. The basic molecular structure unit is composed of a β-1,4-linked glucose chain with a trisaccharide composed of mannose-glucuronic acid-mannose on every second glucose molecule which is partly esterified with acetic-and pyruvic acid [19,20]. These side chains are negatively charged and are able to bind sodium, potassium or calcium ions. ...
... With increasing temperature, the conformation changes from a helical rod to a disordered, more flexible structure which is a reversible process. The rigid conformation of the xanthan gum molecules can be stabilized by low salt concentrations which leads to an increase of the transition temperature [19]. ...
Thesis
The rehydration behavior of food powders is of high importance in terms of powder processing and product quality. Rehydration of powders mainly depends on the physical powder characteristics particle size, porosity and wettability, the latter being expressed by the contact angle between solid and rehydrating liquid. With focus on food powders, it could be shown that the rehydration behavior is strongly influenced by dynamic changes of these physical characteristics. This includes the initiation of dissolution and swelling directly after powder-liquid contact. Especially in case of biopolymers, which were investigated in detail by the example of xanthan gum, guar gum and alginate, these processes are important to describe their rehydration behavior. Due to the special characteristics of these biopolymers dissolution and swelling result in an increase of viscosity as well as in a decrease of bulk porosity. The kinetics and interactions of these processes significantly affect the individual steps of rehydration and have to be considered in describing the process of food powder rehydration. For inert powder-liquid systems capillary liquid uptake into a powder bulk can be described by the Washburn equation which equates the capillary pressure and the hydrodynamic flow resistance. This approach was used as basic equation to describe capillary liquid uptake of food powders. The validity of the original approach is restricted to the case of constant powder and liquid properties. With regard to food powders, changes within the powder-liquid system were considered by a stepwise adaption of the variables of the Washburn equation. Thus, the first part of this thesis focused on establishing and defining methods to characterize the dynamics of the physical properties particle size, bulk porosity, viscosity and contact angle. This enabled a more detailed characterization of the interactions between food powder and liquid during rehydration. Wettability of food powders in contact with dist. water was assessed by contact angle measurements. Contact angles were 52° for alginate, 58.1° for xanthan gum and 70° for guar gum which confirmed their hydrophilic character. To describe the change of the bulk porosity a rheological measurement set-up was constructed to quantify the swelling behavior. Influence of viscosity on rehydration was determined by measuring the concentration dependent viscosity increase and the rate of viscosity increase over time. The change of viscosity as a consequence of dissolution allowed conclusions about the dissolution rate of biopolymers in highly concentrated situations. These results indicated that rehydration of guar gum is mainly influenced by viscosity effects whereas swelling has the highest impact on the rehydration behavior of xanthan gum and alginate. Further methods such as Nuclear Magnetic Resonance analysis enabled a more detailed characterization concerning the dynamics of powder-liquid interactions and the strength of water binding within these biopolymer gels. The strength of water binding was found to correlate with the stability of highly concentrated biopolymer aggregates. The aggregate stability was determined by rheological analyses and is of importance, particularly with regard to powder dispersability. To predict food powder rehydration, a model was established using a VoF approach. To simulate capillary liquid rise based on physical characteristics, dynamic changes were resolved both spatial and temporally. To describe particle and liquid properties more precisely, a model system consisting of biopolymer coated glass beads was developed by fluid bed technology. By the variation of the coating layer thickness and the coating material, dynamic changes within the system could be controlled which enabled a more differentiated description. A parameter variation study was conducted to simulate the influence and interaction of dynamic processes on capillary liquid uptake into such powder systems. Capillary liquid uptake into the coated glass beads was investigated experimentally. It could be shown that even with coating layers of 0.5 µm dynamic effects are sufficiently strong to cause a stop of capillary liquid uptake. It has been shown that viscosity development dominates guar gum rehydration whereas swelling is the prevalent mechanism in xanthan gum and alginate rehydration. Simulation of capillary liquid rise demonstrated that the influence of the coating layer thickness is not significant. This result could be explained by the slow dissolution rates of the biopolymer samples. Calculations indicated that even a coating layer of 0.5 µm could only be dissolved partially after a dissolution time of 250 s. This explains the little impact of coating layer thickness on viscosity development and thus on capillary liquid uptake. Further explanations focus on biopolymer swelling. Simulation showed that coating layers of 0.5 µm are sufficient to cause swelling-induced pore-blocking conditions.
... The degree of pyruvate substitution varies between 30% and 50%, whereas 60-70% of the internal mannose molecules are acetylated. The pyruvyl and acetyl content depends on the fermentation conditions and the bacterial strain (Sworn, 2009;Draeger et al., 2011;Voragen et al., 2012). Average reported composition of polysaccharides produced by X. campestris bacteria is 30.1% D-glucose, 27.3% D-mannose, 14.9% D-glucuronic acid, 7.1% pyruvate and 6.5% acetate . ...
... Xanthan gum is a cream-coloured powder, soluble in water. While xanthan gum will not dissolve directly in alcohol, solutions of xanthan gum are miscible with alcohol and products containing alcohol, and can be formulated to contain up to 60% water-miscible solvents such as ethanol (Sworn, 2009). According to the Belsito et al. (2012) the pH range of a 1% solution (25°C) is 5.5-8.5. ...
Article
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The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of xanthan gum (E 415) as food additive. Following the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010, the Panel considered that adequate exposure and toxicity data were available. Based on the reported use levels, a refined exposure of up to 64 mg/kg bw per day in children for the general population, 38 mg/kg bw per day for children consumers only of food supplements at the high level exposure and 115 mg/kg bw per day for infants consuming foods for special medical purposes and special formulae (FSMPs), were estimated. Xanthan gum (E 415) is unlikely to be absorbed intact and is expected to be fermented by intestinal microbiota. No adverse effects were reported at the highest doses tested in chronic and carcinogenicity studies and there is no concern with respect to the genotoxicity. Repeated oral intake by adults of xanthan gum up to 214 mg/kg bw per day for ten days was well tolerated, but some individuals experienced abdominal discomfort, an undesirable but not adverse effect. The Panel concluded that there is no need for a numerical ADI for xanthan gum (E 415), and that there is no safety concern for the general population at the refined exposure assessment of xanthan gum (E 415) as food additive. Considering the outcome of clinical studies and post-marketing surveillance, the Panel concluded that there is no safety concern from the use of xanthan gum (E 415) in FSMPs for infants and young children at concentrations reported by the food industry. The current re-evaluation of xanthan gum (E 415) as a food additive is not considered to be applicable for infants under the age of 12 weeks.
... Xanthan gum, synthesized by the bacterium Xanthomonas campestris, is a common food additive used as a thickener, particularly in gluten-free foods, where industrial production is worth approximately $0.4 billion each year. Xanthan gum structure consists of (1¡4)-linked ␤-D-glucose with trisaccharide chains containing two mannose and one glucuronic acid residues linked to every other glucose molecule in the backbone, with possible acetylation on the first branching mannose and 3,6-pyruvylation on the terminal mannose (18). These negatively charged side chains give xanthan gum its viscous, gel-like properties. ...
... Dietary alteration may shape the intestinal environment by altering the nutri-ents available or by modulating the concentrations of compounds toxic to C. difficile, such as secondary bile salts. As a common food additive, xanthan gum's physicochemical properties are well known (18). However, its effects on the gut microbiota are poorly understood. ...
Article
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A healthy gut bacterial community benefits the host by breaking down dietary nutrients and protecting against pathogens. Clostridioides difficile capitalizes on the absence of this community to cause diarrhea and inflammation. Thus, a major clinical goal is to find ways to increase resistance to C. difficile colonization by either supplementing with bacteria that promote resistance or a diet to enrich for those already present in the gut. In this study, we describe an interaction between xanthan gum, a human dietary additive, and the microbiota resulting in an altered gut environment that is protective against C. difficile colonization.
... For the starch-based coating materials, the peak in the DSC thermograms can be attributed to the dissociation in the double helix of amylopectin [54]. XG is a polysaccharide with a linear and branched chain structure [55], and GA is a mixture of glycoproteins and polysaccharides with branched chains [56]. Therefore, gums with structures similar to starch-based coating materials may result in the peak in the DSC thermograms of XG and GA. ...
... The inconsistency of the gum-coated microparticles may be caused by their high solubility in an aqueous solution. GA and XG can readily dissolve in water at low temperatures (below 60 °C) [55,56], while starches usually dissolve in water after gelatinization with heat treatment [58]. The high solubility of GA and XG can lead to a rapid disintegration of the the coating material and a rapid release of NaCl from the gum-coated microparticles. ...
Article
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Advanced glycation end products (AGEs), which are present in heat-processed foods, have been associated with several chronic diseases. Sodium chloride (NaCl) modulates the formation of furfurals and acrylamide in the Maillard reaction; however, the effects of NaCl on AGE formation are inconsistent. In this study, we investigated the effects of NaCl on pyrraline formation using glucose-lysine model systems. NaCl, especially at 0.50%, promoted Maillard browning and pyrraline formation, with a simultaneous increase in the 3-deoxyglucosone concentration. To reduce the rate of pyrraline formation, NaCl coated with different gums and starches were used. The results showed that NaCl encapsulation is an effective approach to mitigate pyrraline and 3-deoxyglucosone formation. The content of NaCl in the microparticles were 284 ± 12, 269 ± 6, 258 ± 8, 247 ± 10, 273 ± 16, and 288 ± 15 mg/g (coated with waxy maize starch, normal maize starch, HYLON VII high amylose maize starch, gelatinized resistant starch, xanthan gum, and gum arabic, respectively). The heat resistance of the coating material was negatively correlated with the pyrraline and 3-deoxyglucosone formation, whereas the solubility of the coating material had the opposite results. Coating the material with gum had little effects on the reduction of pyrraline and 3-deoxyglucosone.
... For instance, the surface roughness would affect the optical properties in electrophoresis displays [67,76], which can be adjusted via hydrocolloid type and concentrations. Synergistic effects between hydrocolloids, such as agar with LBG or XG with galactomannans (LBG and guar gum), [77,78] may enable further tuning mechanical properties. ...
... XG was more effective in viscosity modification (Fig. 3(d)) due to its molecules forming an orderly network of intermolecular aggregates and entanglements via hydrogen bonding (−OH⋯H) in solution [78]. Higher XG concentrations did deteriorate capsule quality likely as a result of thinner shells leading to weaker mechanical strength and collapsing after drying. ...
Article
A series of norm-defying hydrocolloid emulsifiers is reported for the challenging task of outstanding long-term retention of volatile cryogenic phase change materials (cryoPCM) in high-payload capsules. Their identification lifted previously imposed restrictions on emulsifier selection in order to fine-tune the mechanical and barrier properties, shell thickness, size and surface roughness of capsules. The exceptionally large payload in terms of both volume (~97 vol%) and weight (~95 wt%), superb long-term retention capability tested at ambient conditions up to 30 days, as well as the surprising cryo-temperature survival of synthesized capsules promote them as immensely efficient candidate carriers for cryogenic thermal energy storage and transport. Utilization of appropriate hydrocolloids and concentrations not only bestows the thermosetting polymeric shells with flexibility, but also eliminates the majority of imbedding satellite particles producing exterior surfaces comparable to a two-step synthesis route ever reported. Promising fatigue resistance within an extreme dynamic temperature range between 20 °C and −140 °C during preliminary cycling tests has been demonstrated via direct observation of capsule buckling and restoration. Such findings provide fundamental insights into achieving superior capsule quality and their far-reaching impacts beyond cryogenic energy storage on applications such as less harsh cold chain logistics, electrophoresis displays, battery safety management and self-healing materials.
... Figure 4 shows the dynamic viscosity of our solution as a function of the applied shear rate together with the fitted Carreau model with parameters µ 0 = 0.085 Pa · s, µ ∞ = 0.001 Pa · s, λ = 2 s, n = 0.48 and α = 0.8 (Equation 4). Very high shear rates have not been measured, but literature values [36] indicate that the viscosity of xanthan gum solutions approach the viscosity of water at high shear rates. ...
... Very high shear rates have not been measured. Literature values indicate that µ ∞ for xanthan gum solutions approximates water, i.e., µ ∞ = 0.001 Pa s[36]. ...
Article
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When non-Newtonian fluids flow through porous media, the topology of the pore space leads to a broad range of flow velocities and shear rates. Consequently, the local viscosity of the fluid also varies in space with a non-linear dependence on the Darcy velocity. Therefore, an effective viscosity μeff is usually used to describe the flow at the Darcy scale. For most non-Newtonian flows the rheology of the fluid can be described by a (non linear) function of the shear rate. Current approaches estimate the effective viscosity by first calculating an effective shear rate mainly by adopting a power-law model for the rheology and including an empirical correction factor. In a second step this averaged shear rate is used together with the real rheology of the fluid to calculate μeff. In this work, we derive a semi-analytical expression for the local viscosity profile using a Carreau type fluid, which is a more broadly applicable model than the power-law model. By solving the flow equations in a circular cross section of a capillary we are able to calculate the average viscous resistance 〈μ〉 directly as a spatial average of the local viscosity. This approach circumvents the use of classical capillary bundle models and allows to upscale the viscosity distribution in a pore with a mean pore size to the Darcy scale. Different from commonly used capillary bundle models, the presented approach does neither require tortuosity nor permeability as input parameters. Consequently, our model only uses the characteristic length scale of the porous media and does not require empirical coefficients. The comparison of the proposed model with flow cell experiments conducted in a packed bed of monodisperse spherical beads shows, that our approach performs well by only using the physical rheology of the fluid, the porosity and the estimated mean pore size, without the need to determine an effective shear rate. The good agreement of our model with flow experiments and existing models suggests that the mean viscosity 〈μ〉 is a good estimate for the effective Darcy viscosity μeff providing physical insight into upscaling of non-Newtonian flows in porous media.
... Xanthan gum is composed of a (1-4)-linked β-D-glucose backbone with a trisaccharide chain on every other glucose at C-3, containing a glucuronic acid residue linked (1-4) to a terminal mannose unit and (1-2) to a second mannose that connects to the backbone (Sworn, 2009). Xanthan gum is an extracellular polysaccharide secreted by the bacterium Xanthomonas campestris. ...
... Hence, the HM-pectin/alginate gel have the higher amount of carboxyl groups of the gel systems used here. Xanthan, on the other hand, is only weakly charged, carrying a glucuronic acid residue on the trisaccharide side chain connected to every other glucose of the backbone and further contains pyruvate to a maximum of 50% of the terminal mannose residues (Labille et al., 2005;Sworn, 2009), and can be considered as a low-conductive. As the backbone of agarose and LBG is uncharged (Serwer, 1983;Fatin-Rouge et al., 2003), the xanthan/LBG and the xanthan/LBG/agarose gels were expected to exhibit low electrical conductivity, which was indeed demonstrated (Figure 1). ...
Article
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The feasibility of using hydrogels as a water bolus during hyperthermia treatment was assessed. Three types of gels, high methoxyl (HM) pectin/alginate, xanthan/locust bean gum (LBG) and xanthan/LBG/agarose were evaluated based on their dielectric properties, rheological and mechanical properties. The most suitable, xanthan/LBG/agarose, gel was further used as a water bolus in a hyperthermia array applicator. The gels composed of polysaccharides carrying low charge displayed dielectric properties close to those of water, while the dielectric properties of HM pectin/alginate gel was deemed unsuitable for the current application. The mechanical examination shows that the xanthan/LBG gel has a non-brittle behaviour at room temperature, in contrast to the agarose gel. The moduli of the xanthan/LBG gel weaken however considerably between the temperature range of 40 and 50°C, reducing its potential to be used as water bolus. The ternary system of xanthan/LBG/agarose had advantageous behaviour as it was dominated by the thermal hysteresis typical of agarose upon temperature increase, but gov- erned by the typical non-brittle behaviour of the xanthan/LBG at low temperatures. The final evaluation within the hyperther- mia applicator showed excellent signal transmission from the antennas. The agarose/xanthan/LBG gel reduced the scattering of electromagnetic waves, enabled a tight closure between the body and the antennas, and offered a less bulky solution than the currently used water-filled plastic bags. The results presented here open up a new application area for hydrogels in improving heat delivery during hyperthermia treatment and other near-field microwave applications.
... The n values (0.13∼0.17) of XG/LBG/HPMC ternary mixtures were lower than that (0.18) of the XG/LBG binary mixture, and the n value (0.13) of the sample with 5% HPMC was the smallest compared with those (0.14∼0.21) of other samples. It is known that liquids with lower n val- ues could provide good mouthfeel (20). A study (6) has also reported that higher shear-thinning behavior allows thickened liquids to be swallowed easily and reduces organoleptic sliminess during swallowing, resulting in a pleasant and light mouthfeel. ...
Article
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The effects of cellulose gums (CG), such as carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC), on the flow and dynamic rheological properties of binary mixtures of xanthan gum (XG) and locust bean gum (LBG) were examined at different XG/LBG/CG mixing ratios (50/50/0, 47.5/47.5/5.0, 45/45/10, and 42.5/42.5/15.0). All XG/LBG/CG ternary mixtures showed high shear-thinning behavior and the flow behavior index values of samples containing HPMC were lower than those of samples containing CMC. An increase in consistency index and apparent viscosity values was observed for ternary gum mixtures containing HPMC, indicating that the flow properties of the XG/LBG binary mixture were affected by the content of HPMC. Storage modulus and loss modulus values of ternary gum mixtures decreased with an increase in CG content from 5 to 15%. The maximum viscoelasticity of XG/LBG/CG mixtures was observed at a mixing ratio of 47.5/47.5/5.0. These findings suggest that the rheological properties of XG/LBG binary mixtures were strongly influenced by the addition of CMC and HPMC.
... The response of hydrocolloid viscosity to temperature is significant in food industry, since most heating processes experience a range of temperatures and the temperature response may vary with hydrocolloid source. For example, xanthan gum can maintain viscosity at high temperature (Sworn, 2000), while many watersoluble polysaccharides have a drop of viscosity with increasing temperatures (Farhoosh & Riazi, 2007;Yang & Zhu, 2007). As shown in Fig. 5A, the viscosity of each tara gum solution decreased when temperature increased from 30°C to 80°C, indicating the temperature dependence of the gum. ...
Article
The rheological properties of tara gum, as affected by concentration, temperature, pH and the presence of salts and sucrose, were investigated by using steady and dynamic shear measurements and atomic force microscope observation. Tara gum exhibited non-Newtonian, pseudoplastic behaviour without thixotropy at tested concentrations (0.2–1.0%, w/v). Salts (CaCl2 and NaCl) led to a viscosity reduction, which was more sensitive to Ca2+ than to Na+. The gum had stable viscosity over a wide pH range (pH 3–11), and the influence of sucrose was concentration dependent. Increasing temperature from 20 °C to 80 °C decreased the gum viscosity. Frequency sweeps indicated that tara gum (1.0% w/v) behaved as a liquid at low frequency, and acted more like a gel at high frequency. With the decrease of concentration, tara gum may show a viscous property rather than an elastic one. These results are potentially useful for the application of tara gum in food processing.
... The surface area-volume ratio of XGMC was larger than that of XG because the former existed as individual particles, so the XG from XGMC could formed hydrate more easily than free XG (Chen, Gross, Yuan, & Talashek, 2002). Furthermore, XG dispersion in aqueous phase also could be improved by separating the gum particles with nonsolvents such as alcohol, glycerol or oils (Sworn, 2009). It could be speculated that the gum particles in microcapsules were still separated by PS and BW after melting in the initial hydration stage. ...
Article
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Xanthan gum microcapsules (XGMC) were prepared by phase separation method based on palm stearin/beeswax (PS/BW) systems. XG microcapsules with high encapsulation efficiency were obtained at the preparation conditions of PS‐to‐BW ratio 7:3 and core‐to‐wall ratio 10:10. The inverted micrograph showed that the shapes of XGMC were mainly spherical, and the particle sizes of XGMC were chiefly distributed in the range from 40 to 300 μm. The XGMC curve of differential scanning calorimetry (DSC) illustrated that two peaks appeared at around 40 and 60°C, and the two temperatures were in accordance with the melting points of PS and BW, respectively. Compared with that of XG, the hygroscopicity of XG in microcapsules was obviously decreased under medium and high humidity conditions. Viscosity measurements showed that XGMC could be destructed and XG was completely released from microcapsules at temperature above 65°C. The XG released from microcapsules could more fast hydrate than XG, and “fish‐eye” would not be formed. Microencapsulation could be an effective method to protect XG from high hygroscopicity, to promote the polysaccharide hydration process, and to prevent the “fish‐eye” formation. Practical Applications XG as a hydrophilic polysaccharide is able to strongly absorb moisture and form agglomerates during storage. Moreover, the gum tends to produce “fish‐eye” formation during hydration process. These shortcomings are not propitious for XG applications in the food processing industry. Microencapsulation is usually employed to improve the physicochemical properties of active ingredients. XG was encapsulated into palm stearin/beeswax matrix using phase separation method. The hygroscopicity of XG was reduced significantly after microencapsulation, and the “fish‐eye” formation was also effectively prevented. The hydration rate and efficiency of XG after microencapsulation were obviously enhanced. The XG microcapsules obtained in this work will promote the application in food industry and increase the economic value of XG. In addition, the system of palm stearin/beeswax could be adequately developed as effective wall materials.
... This is possible due to pseudoplasticity of xanthan gum that helps improve suspension and emulsification. This also indicates that xanthan gum is good at holding particles in suspension (Sworn, 2009), thus it may help in preventing microorganisms from consuming stabilized sugars such as glucose and fructose in honey beverages. ...
Article
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Development of ready to drink (RTD) beverage containing honey as a natural ingredient to replace sugary (high calorie) beverage using pasteurization is a new emerging market. However, the stability of the beverage may be affected due to sedimentation in the solution thus the addition of xanthan gum to improve the stability was proposed. Therefore, the objective of this study was to evaluate the effects of pasteurization and different concentrations of xanthan gum (0.05% and 0.1%) on the shelf life and physicochemical properties of honey beverages during storage at 25±2°C. The honey beverages were analyzed for total soluble solids (TSS), pH, rheological behavior, total phenolic content (TPC) and total plate count after processing at a specified time interval until the samples were deteriorated. The beverage containing 0.1% of xanthan gum shows significantly (p<0.05) higher stability in terms of TSS and total plate count than honey beverages containing 0.05% xanthan gum. Both pasteurized 0.05% and 0.1% xanthan gum enriched honey beverages samples remain acceptable in terms of TSS, pH, TPC and total plate count during 10 weeks of storage. On the contrary, all unpasteurized honey beverages were deteriorated after the first week of storage. Thus, pasteurization and addition of xanthan gum of honey beverages are recommended for longer shelf life at room temperature.
... This special behavior results from the ability of xanthan gum to aggregates in solution via hydrogen bonding and polymer entanglement which causes high viscosity of xanthan gum and also accounts for its suspending ability as it can be seen in the results shown in Figure 6 and Figure 7. Xanthan gum solutions have the ability to retain their properties as temperature increases until a definite temperature known as the melting temperature is reached. At this temperature the viscosity drops sharply due to a reversible molecular conformation change [18]. ...
Preprint
The selection and control of a suitable drilling fluid is necessary to successfully drill an oil and gas well. The rheological properties of drilling fluids vary with changes in conditions such as time and temperature. Slight changes in these conditions can cause unpredictable and significant changes in the mud’s properties. This makes it necessary to study the rheology of drilling fluids and how it is affected by these changes. At the rig sites, tests are carried out by the mud engineers to ensure that the properties of the drilling fluids are within the required limits. Similar tests were carried out at the laboratory in this work to determine the plastic viscosity, yield point, gel strength of mud samples at different conditions of ageing time, temperature and concentration of Xanthan gum (X.G) used as an additive. The Experiments carried out were grouped into three. The first was done with the aim to further explain how the Bentonite and Sepiolite water-based drilling fluids behaves after been aged for certain period. The second sets of experiments were conducted to investigate how the rheological properties of water-based Bentonite muds are affected by different concentration of xanthan gum added as an additive to improve the muds properties and the last sets of experiments were done to investigate the ageing effect on Bentonite mud treated with 250mg/L xanthan gum. Effects of temperature were also considered in these experiments with a 10℃ variation in the first group and 20℃ in the other two groups between readings from 20℃ to 60℃ . Results obtained indicated that Sepiolite water-based drilling fluid offers better plastic viscosity and yield point as compared to Bentonite water-based drilling fluids. It was also found that the viscosity and yield point of Sepiolite, Bentonite and treated Bentonite muds decreases with increase ageing time and temperature while the gel strength increases with ageing time but similarly decreases with increase in temperature. In the second group, results obtained indicated that plastic viscosity, yield point and gel strength increases as concentration of xanthan gum increases, all of which decreases with increase in temperature.
... It is known that in aqueous dispersions, highly ordered network of entangled, stiff molecules of xanthan result from intermolecular aggregates formation via hydrogen bonding and polymer entanglements. These structures are responsible for the high viscosity at low shear rates (Sworn, 2009). Therefore, it is likely that plasma treatment increases the hydrogen bonding ability or orderliness of the structures, thereby effecting the low shear viscosity increase. ...
Article
In this work, we report the potential application of cold plasma technology for tailoring the functional properties of hydrocolloids. On treating xanthan gum in solid phase with atmospheric air cold plasma, we observed an increase in the viscosifying ability at low shear rates, and emulsion stabilizing activity of the gum, without affecting the colour or the basic polysaccharide backbone. The observed changes have potential benefits for salad-dressing and instant dry soup formulations.
... The above agrees with the findings reported by Sandolo, Coviello, Matricardi, & Alhaique (2007), who observed that proportions of locust bean gum/xanthan gum between 1:1 and 1:3 produced gels ranging from very rigid to weak. Moreover, Sworn (2009) also suggests that the optimum ratio for the use of locust bean gum/ xanthan gum is 2:3, due to the synergistic interaction of xanthan gum with galactomannans. ...
Article
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Introduction: In making a cream, various additives can be added, among which gums, which have been the subject of interest due to their advantages in industrial production, stand out. Objective: To evaluate the effect of xanthan and locust bean gums on the physical and sensory properties of acidified dairy creams. Materials and methods: The factors studied were: concentration (xanthan gum from 0.025 to 0.5 % and locust bean gum from 0.05 to 0.5 %) and acidity percentage (from 0.5 to 0.65 % in both gums). A mixture design was applied with the concentrations of the two gums studied. The variables viscosity, drainage stability, consistency and adhesiveness were measured instrumentally, while sensorially the consistency, viscosity and acidity were evaluated with a JAR (Just About Right) test using five-point scales, and on the acceptability for attributes and overall acceptability a nine-point hedonic scale was used. Results and discussion: The creams with the greatest acceptability corresponded to concentrations of 0.2 to 0.38 % xanthan gum and 0.46 to 0.5 % locust bean gum. The JAR test showed that the best mixture was the one containing 0.325 and 0.175 % xanthan and locust bean gums, respectively; this last treatment was compared with three commercial creams and one of them presented viscosity and consistency values (10 kg·m⁻¹·s⁻¹ and 4,000 gf, respectively) similar to those of the mixture obtained. Conclusions: It is possible to assume the existence of a masking effect of the sensory perception of acidity due to the high viscosities provided by xanthan gum. On the other hand, the viscosity acceptability and overall acceptability curves showed a maximum.
... Shear thinning is mainly due to the conformation of the side chains flattening against the backbone under shear, so reducing the intermolecular interactions. The relatively low viscosity at high shear means that it is easy to mix, pour and swallow but its high viscosity at low shear lends stability to colloidal suspensions (Bemiller and Whistler, 1996;Rodd et al., 2000;Sworn, 2000). ...
Chapter
The applications of emulsions are numerous. Many products of commercial importance are sold in emulsion form. The industries where emulsions are of considerable importance include petroleum, food, medical and pharmaceutical, cosmetics, agriculture, explosives, polishes, leather, textile, bitumen, paints, lubricants, polymer, and transport, among others. Particularly, food emulsions exhibit a great diversity of rheological characteristics, ranging from low-viscosity Newtonian liquids (e.g., milk, fruit beverages), to viscoelastic materials (e.g., salad dressings) and to plastic materials (e.g., butter). This diversity is the result of the different sorts of ingredients and processing conditions used to create each unique type of product. Polysaccharides are usually added to the aqueous phase of low-in-fat o/w food emulsions to improve their creaming stability. Their efficiency depends on polymer concentration in the aqueous phase as well as on the structural features of the aqueous polymer system. Xanthan gum is one of the hydrocolloids most used as emulsion stabilizer because of its unique rheological behavior. It forms highly viscous shear thinning solutions at very low concentrations and the viscosity is not influenced to any great extent by changes in pH, the presence of salts and temperature. The high viscosity at low shear enables the gum to prevent particle sedimentation and droplet creaming and the shear thinning characteristics ensure that the product readily flows from the bottle after shaking. The present chapter is oriented to interpret and model the rheological behavior of oil-in-water emulsions stabilized singly with xanthan gum or combined with different hydrocolloids, like guar gum or potato starch. The effect of hydrocolloids concentration was studied using oscillatory measurements within the linear viscoelastic range. Viscoelastic behavior of the systems was satisfactorily modeled using generalized Maxwell equation. This empirical model was used to predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Flow properties were determined through rotational experiments and changes during storage time were analyzed using parameters of the Cross model on the flow curves. Droplet size distribution was measured by image analysis. Microscopic observations revealed that emulsions containing xanthan gum did not significantly change the average droplet diameter during the first month of storage. Visual inspections of the formulated emulsions showed that they remained stable after six months even emulsions with low oil content (10%).
... 11 Xanthan gum forms a viscous solution in water with pseudoplastic ow behaviour but when mixed with locust bean gum in a 1 : 1 ratio, a large increase in viscosity is seen at low concentrations and gelation occurs at overall polymer concentration as low as 0.3%. 12 Agar consists of both agarose and agaropectin, with the former being the constituent that causes gelation. Agarose is composed of a linear polymer of the disaccharide D-galactose and 3,6-anhydro-L-galactopyranose and is insoluble in cold water but hydrates at temperatures close to the boiling point of water where its molecules have a random coil conformation (see Scheme 1). ...
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We report a binary hydrogel system made from two food grade biopolymers, agar and methylcellulose (agar–MC), which does not require addition of salt for gelation to occur and has very unusual rheological and thermal properties. It is found that the storage modulus of the agar–MC hydrogel far exceeds those of hydrogels from the individual components. In addition, the agar–MC hydrogel has enhanced mechanical properties over the temperature range 25–85 °C and a maximum storage modulus at 55 °C when the concentration of methylcellulose was 0.75% w/v or higher. This is explained by a sol–gel phase transition of the methylcellulose upon heating as supported by differential scanning calorimetry (DSC) measurements. Above the melting point of agar, the storage modulus of agar–MC hydrogel decreases but is still an elastic hydrogel with mechanical properties dominated by the MC gelation. By varying the mixing ratio of the two polymers, agar and MC, it was possible to engineer a food grade hydrogel of controlled mechanical properties and thermal response. SEM imaging of flash-frozen and freeze-dried samples revealed that the agar–MC hydrogel contains two different types of heterogeneous regions of distinct microstructures. The latter was also tested for its stability towards heat treatment which showed that upon heating to temperatures above 120 °C its structure was retained without melting. The produced highly thermally stable hydrogel shows melt resistance which may find application in high temperature food processing and materials templating.
... The viscosity of the liquid extracts increased with the addition of xanthan gum, which was used as a drying agent (Fig. 1). The results show that the sisal extract without xanthan gum has a Newtonian behavior (flow index n = 1), whereas the samples formulated with xanthan gum (0.25 and 0.5%) show a pseudoplastic behavior (flow index n b 1), where the apparent viscosity decreases with the increase in shear rate, as reported by Sworn [19]. ...
Article
Background The number of persons with difficulty in mastication and swallowing is increasing and causes a social problem. Commercially available soft gels for disadvantaged persons are known to be crushed between the tongue and the hard palate, but the detailed mechanism is not well understood. Scope and approach After reviewing the safety and difficulty in eating, the significance of the tongue pressure is discussed. To avoid the complexity of the simultaneous action of the teeth and the tongue, squeezing with the tongue without teeth is studied. Squeezing of gels with different deformabilities between the tongue and palate is analyzed using an ultrathin sensor, and compared with the in vitro test using an artificial tongue and panellists’ judgements of the strategy change from tongue-palate compression to chewing. Key findings and conclusions It was clarified that the work of the tongue just before swallowing depends not only on the initial mechanical properties of foods but also on the oral processing before the swallowing. This poses a question on the prevailing view that the final mechanical properties just before swallow does not depend on the initial mechanical properties of ingested foods. The transition of the strategy from the tongue-palate squeezing to the teeth chewing was shown to be determined using an artificial tongue compression approach in combination with sensory evaluation to select the strategy. These findings can be a basis for understanding better the conditions necessary for designing food gels. The tangential force during squeezing should be analyzed in the future.
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Rehydration of biopolymer powders is influenced by dissolution, viscosity development and swelling. Associated dynamic changes of powder characteristics correlate with their rehydration properties. Especially floating and particle aggregation negatively affect the rehydration process and powder quality. A deeper knowledge about these dynamics is crucial with regard to product development and quality improvement. The dynamics of swelling and viscosity development are of special importance. Controlling these parameters by a targeted modification will improve the rehydration process. Within this study the rehydration behavior of xanthan gum, guar gum and alginate was analyzed. Focus was on investigating their dynamic behavior and providing a detailed description of the rehydration process. Experiments were carried out using a model system, consisting of biopolymer coated glass beads. Rehydration was investigated experimentally and by simulation. The importance of dynamic effects and their mutual interaction was demonstrated. Results explain the mechanisms of the dynamic rehydration process of food powders.
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The physicochemical and rheological properties of aqueous solutions of the mucilage isolated from Opuntia ficus indica (L. Mill) at different concentration (0.5, 1, 1.5 and 4.5% w/v) were examined. The intrinsic viscosity [η] found for precipitate mucilage (PM) and dialyzed mucilage (DM) were 22.6 and 15.3 dl/g respectively. Electrophoretic measurements showed that the zeta potential of PM and DM was negative in all the pH range studied. PM reduced the surface tension of water and was concentration dependent. The surface activity of PM (57 mN/m) was similar to that of guar gum (55 mN/m) and xanthan gum (52 mN/m) at 1.5% (w/v) concentration. A non-Newtonian shear-thinning behavior was observed. The Ostwald–de Waele model successfully correlated the viscosity–shear rate. At equal hydrocolloid concentration, the consistency coefficients (k) of mucilage solutions were lower than those of guar gum (GG) and xanthan gum (XG). However, the consistency coefficient of a mucilage solution at 4.5% (w/v) (20.9 Pa s) was in the same order as that shown by GG at 1.5% (w/v) (28.8 Pa s) aqueous solution. No effects of pH and ionic strength on the viscosity of PM and DM were observed. The mechanical spectra showed a crossover point between G′ and G″ at low mucilage concentrations of 0.5 and 1% (w/v), exhibiting higher relaxation time than GG. The more concentrated solutions of PM and DM (1.5 and 4.5% w/v) displayed a predominant elastic behavior and did not meet the Cox-Merz rule, similarly to GX. The more concentrated solutions of PM and DM did not meet the Cox-Merz rule. This behavior would suggest the formation of colloidal aggregates.
Article
Gleditsia triacanthos polysaccharide, known as galactomannan, has not been exploited as a new functional material even though it possesses industrial potential in food and biomedicine. Galactomannans were recovered from the endosperm of seeds (15 weeks to 25 weeks after flowering) for deposition and maturation analysis. These galactomannans were characterized by using Nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and monosaccharide composition analysis (particularly the mannose to galactose ratio) and molecular weight, solubility, and rheological measurements. The ratio of the three parts in mature seeds was as follows: endosperm (36.67%), hull (34.41%), and embryo (28.92%). The M/G ratio increased from 2.53 to 3.24 between 15 and 23 weeks and then decreased to 3.16 in 25 weeks, consistent with the trends of rheology and solubility. The molecular weight (1.28 × 106 g/mol) and intrinsic viscosity (882.53 mL/g) reached the maximum at 23 weeks and then decreased. Additionally, NMR and XRD showed that the M/G ratio did not change the basic chemical structure but caused slight changes in crystallinity. The purpose of the study was to reveal the changes in galactomannan structure, rheology, and solubility during G. triacanthos galactomannan deposition and maturation to facilitate exploration of its potential industrial applications.
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The interactions between xanthan gum (XG) and dodecyltrimethylammonium bromide (DTMAB) are studied by static and dynamic light scattering, microrheology and viscometry within the overlapping regime of aqueous xanthan solutions. In the absence of salt mixing with surfactant transforms the complex fluid of interconnected xanthan chains into diffusing aggregates because of the reduction of the polysaccharide’s effective charge and the introduction of hydrophobic units. In the presence of salt the effect of complexation is weaker. Mixing the two components while XG is in its denatured state results to a network with reduced interchain connections. Linear (microrheological) and nonlinear (steady shear) viscoelastic experiments show that there is a significant compromise of the viscoelastic moduli which is remarkably more intense when mixing DTMAB with XG in its denatured state. These findings prove that xanthan’s viscoelastic and morphological properties may be tuned by addition of surfactants and that the conformational state of XG during complexation is a defining parameter.
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Absence of gluten in bakery goods is a technological challenge, generating gluten-free breads with low functional and nutritional properties. However, these issues can be minimized using new protein sources, by the addition of nutritional added-value products. Fresh yogurt represents an interesting approach since it is a source of protein, polysaccharides, and minerals, with potential to mimic the gluten network, while improving the nutritional value of gluten-free products. In the present work, different levels of yogurt addition (5% up to 20% weight/weight) were incorporated into gluten-free bread formulations, and the impact on dough rheology properties and bread quality parameters were assessed. Linear correlations (R2 > 0.9041) between steady shear (viscosity) and oscillatory (elastic modulus, at 1 Hz) values of the dough rheology with bread quality parameters (volume and firmness) were obtained. Results confirmed that the yogurt addition led to a significant improvement on bread quality properties, increasing the volume and crumb softness and lowering the staling rate, with a good nutritional contribution in terms of proteins and minerals, to improve the daily diet of celiac people.
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With the continuing efforts to explore alternatives to petrochemical-based polymers and the escalating demand to minimize environmental impact, bio-based polymers have gained a massive amount of attention over the last few decades. The potential uses of these bio-based polymers are varied, from household goods to high end and advanced applications. To some extent, they can solve the depletion and sustainability issues of conventional polymers. As such, this article reviews the trends and developments of bio-based polymers for the preparation of polymer electrolytes that are intended for use in electrochemical device applications. A range of bio-based polymers are presented by focusing on the source, the general method of preparation, and the properties of the polymer electrolyte system, specifically with reference to the ionic conductivity. Some major applications of bio-based polymer electrolytes are discussed. This review examines the past studies and future prospects of these materials in the polymer electrolyte field.
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Biomimetic hydrogels composed of natural polysaccharides have invariably blossomed as niche biomaterials in tissue engineering applications. The prospects of creating an extracellular matrix (ECM)-like milieu from such hydrogels has garnered considerable importance. In this study, we have fabricated bioscaffolds comprising dialdehyde alginate and xanthan gum and explored their potential use in tissue regeneration. The fabricated scaffolds displayed an interconnected porous network structure that is highly desirable for the aforesaid application. The scaffolds were endowed with good mechanical properties, thermostability, protein adsorption efficacy and degradability. Curcumin-loaded hydrogels exhibited appreciable antibacterial activity against E. coli. In vitro cytocompatibility studies revealed that the scaffolds promoted adhesion and proliferation of 3T3 fibroblast cells. The Western blot analysis of p53 gene indicated no growth arrest or apoptosis in 3T3 cells thus, signifying the non-toxic nature of the scaffolds. Furthermore, the ECM formation was confirmed via SDS-PAGE analysis. The overall results clearly validated these scaffolds as effectual biomaterials for tissue engineering applications.
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The water content in gluten-free recipes plays an essential role in the resulting product quality. Up to date the water adjustment is conducted mainly by trial-and-error. Brabender GmbH & Co. KG developed an attachment for the Farinograph, which makes the measurement of batter consistencies feasible. The water content was adjusted using this new tool and compared to the water determined based on the water hydration capacity (WHC) of the single bulking ingredients. Furthermore, bread quality characteristics were analysed. Five different hydrocolloids were tested in a gluten-free system based on rice flour. Water levels differed significantly, when guar gum (20% water) or sodium alginate (18% water) were incorporated. The use of Farinograph resulted generally in a higher specific volume (+0.63 ml/g) and a softer crumb (−16 N). On the contrary, the WHC-method only gave an indication about the water addition but did not consider temperature changes during mixing and its effect on the hydration. In conclusion, Farinograph can be considered as a useful tool for the determination of the optimal water content, and additionally provides useful information about batter stability and dough development time.
Chapter
The term gum is referring to a group of polysaccharides with various commercial functionalities which can create aqueous viscous dispersions and gels and stabilize different types of emulsion systems at low concentrations except for gum Arabic and some specific gums with low viscosity which need high concentrations even up to 10% to play their functions. Natural gums are considered as high molecular weights hydrophilic carbohydrate which can partially or completely dissolve or swell in water to produce colloidal dispersions with various mechanical and rheological properties. During the last decades, these natural hydrocolloids have been attractive alternatives to synthetic polymers as they are mostly inert, inexpensive, biocompatible, safe, odorless, and easily available. Therefore, this chapter reviews the important and practical natural gums with a wide range of applications in the pharmaceutical, cosmetic, and food industries.
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Food behavior during oral processing plays an essential role in the perception of texture. It depends on different factors, including food structure and composition, as well as its behavior when interacting with saliva. This study aimed to investigate the effect of particle size and thickener type of emulsified systems on physical, rheological, tribological, and oral oily coating properties under oral conditions. Six matrices based on oil-in-water emulsions with different particle sizes (NE-nanoemulsion and CE-conventional emulsions) were prepared using a mixture of emulsifiers (10% w/w) and sunflower oil (10% w/w). Thickened agents were added to the matrices (NE and CE) at different concentrations (3–4.5% w/w of starch-ST or 0.4–0.8% w/w xanthan gum-XG) to obtain equi-viscous samples (NE-EV) with their CE-based counterpart. Results showed a decrease in apparent viscosity values under oral conditions (saliva and shearing at 10 s⁻¹) during the shear time, but this behavior was more evident in starch-based matrices. The lubrication properties of the different matrices depended mainly on the thickener concentration since equi-viscous samples (NE-ST-EV and NE-XG-EV) showed higher coefficient of friction (CoF) values. Finally, oral oily coating was more related to the oil droplets size than to the type of thickener since all NE-based matrices showed a higher amount of coating retained compared to the CE-based ones. Therefore, NE-based matrices could be used as an alternative to increase mouthfeel sensations in food emulsions.
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Plant-based foods with desirable texture and nutritional value have attracted considerable interest from consumers. In order to meet the growing demand for more sustainable and health-focused products, new sources for plant-based products are needed. In this study, we aimed to develop an innovative plant-based dessert based on the underutilized crop chufa tubers (Cyperus esculentus). The chufa extract was fermented with plant-adapted lactic acid bacteria and formulated with the purpose of imitating the Danish summer dessert “cold butter-milk soup”. The effect of various bacterial fermentations and formulations on steady and oscillatory rheology, stability, dry matter, pH, and sugar profile of the product were studied and compared to a commercial cold buttermilk soup sample. A strain of Leuconostoc mesenteroides was found to create the most similar taste to a commercial sample. By adding lemon juice, sucrose, xanthan gum, and vanilla to the fermented chufa drink, the drink was found to mimic the pH, texture, acid profile, and stability of a commercial dairy-based sample, while containing a lower concentration of carbohydrates.
Chapter
Drilling fluids have evolved from humble beginnings into advanced technology responsible for many critical functions in well construction. Essential functions such as formation pressure management, wellbore stabilization, and cuttings transport are derived from the physical and chemical properties of the drilling fluid, and these properties result from the underlying fluid design and formulation of chemical additives. Throughout the history of well construction, the suite of accessible chemical additives and fluid formulations along with knowledge of how these chemistries interact with the formation during drilling has increased significantly. These advancements have resulted in enhanced fluid performance allowing for the successful drilling of increasingly complex wells. In this chapter, a comprehensive analysis will be performed on drilling fluid functions, properties, formulations, and applications for a range of fluid systems including conventional clay-based aqueous systems and emulsion-based nonaqueous systems, reservoir drilling fluids, and the more recently developed high-performance aqueous and nonaqueous fluids.
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Ultrasound, alone or in combination with natural antimicrobials, is a novel food processing technology of interest to replace traditional food decontamination methods, as it is milder than classical sterilisation (heat treatment) and maintains desirable sensory characteristics. However, ultrasound efficacy can be affected by food structure/composition, as well as the order in which combined treatments are applied. More specifically, treatments which target different cell components could result in enhanced inactivation if applied in the appropriate order. The microbial properties i.e. Gram positive/Gram negative can also impact the treatment efficacy. This work presents a systematic study of the combined effect of ultrasound and nisin on the inactivation of the bacteria Listeria innocua (Gram positive) and Escherichia coli (Gram negative), at a range of cavitation conditions (44, 500, 1000 kHz). The order of treatment application was varied, and the impact of system structure was also investigated by varying the concentration of Xanthan gum used to create the food model systems (0 – 0.5% w/v). Microbial inactivation kinetics were monitored, and advanced microscopy and flow cytometry techniques were utilised to quantify the impact of treatment on a cellular level. Ultrasound was shown to be effective against E. coli at 500 kHz only, with L. innocua demonstrating resistance to all frequencies studied. Enhanced inactivation of E. coli was observed for the combination of nisin and ultrasound at 500 kHz, but only when nisin was applied before ultrasound treatment. The system structure negatively impacted the inactivation efficacy. The combined effect of ultrasound and nisin on E. coli was attributed to short-lived destabilisation of the outer membrane as a result of sonication, allowing nisin to penetrate the cytoplasmic membrane and facilitate cell inactivation.
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Nanotechnology has proven as progressive technology that enables to contribute, develop several effective and sustainable changes in food products. Incorporating nanomaterials like TiO2, SiO2, Halloysite nano clay, Copper sulfide, Bentonite nano clay, in carrageenan to develop innovative packaging materials with augmented mechanical and antimicrobial properties along with moisture and gas barrier properties that can produce safe and healthy foods. Intervention of carrageenan-based bio-nanocomposites as food packaging constituents has shown promising results in increasing the shelf stability and food quality by arresting the microbial growth. Nanomaterials can be incorporated within the carrageenan for developing active packaging systems for continuous protection of food products under different storage environments from farm to the fork to ensure quality and safety of foods. Carrageenan based bio nanocomposite packaging materials can be helpful to reduce the environmental concerns due to their high biodegradability index. This review gives insight about the current trends in the applications of carrageenan-based bio nanocomposites for different food packaging applications.
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Currently gels or dispersions are widely used in the restoration of paintings, graphic arts, stuccoworks and stones, but their use in metal restoration is less widespread. In this study, several gels and dispersions were selected for use in metal treatments. These gels and dispersions have been tested as a support for the treatment solutions usually used for chemical treatments of metals. First, the compatibility of these physical and chemical gels or dispersions with selected treatment solutions was checked. Viscous physical gels (Xanthan gum), collagen-based physical gels (nerve glue), chemical gels (Nanorestore gels®) or dispersions (polyacrylic acid, cellulose-based compound) displayed good compatibility with acid, neutral or basic solutions. Physical peelable gels (Agar or gellan gum) displayed more limited compatibility but were more easily applied on metallic objects. Test treatments were carried out on archaeological objects: silver-plated copper alloy coins. The best post-treatment results in terms of efficiency and the overall aesthetic appearance of the object were obtained with physical peelable gels (Agar or gellan gum) containing a treatment solution (2–5%w of disodium EDTA), applied hot.
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With the speeding tendency of aging society, the population experienced dysphagia is increasing quickly. Desirable dysphagic diets should be safe, visually appealing and nutritious. 3D printing allows for creation of personalized nutritious foods with regular-like appearance. Shiitake mushroom, rich in protein and bioactive compounds, is suitable for elderly, but its hard texture was not friendly to the elderly with dysphagia. This study investigated the feasibility of production of dysphagic product using shiitake mushroom by 3D printing with various gums addition, including arabic gum (AG), xanthan gum (XG) and k-carrageenan gum (KG) at concentrations of 0.3%, 0.6% and 0.9% (w/w). Data suggested that XG and KG incorporation significantly increased inks’ mechanical strength by decreasing water mobility and promoting the formation of hydrogen bond, enabling 3D printed objects with great self-supporting capacity. The XG containing and KG-0.3% samples were categorized into level 5—minced and moist dysphagia diet within international dysphagia diet standardization initiative (IDDSI) framework. AG addition decreased mechanical strength and viscosity, hardness and self-supporting capacity of 3D printed constructions. AG-0.3% and AG-0.6% samples could not be classified as dysphagia diets based on IDDSI tests. This study provides useful information for dysphagia diet development with appealing appearance by 3D printing.
Article
With the aging population trend, there is a great demand for dysphagia diet as the elderly suffering from dysphagia is increasing rapidly. 3D printing is capable of processing mashed and not attractive dysphagia diet into appetizing foods with appealing appearance. Black fungus (Auricularia auricula) illustrates many health-promotion effects, but its elastic texture and great chewing efforts making it unfeasible for the elderly. In this work, we studied the feasibility to develop 3D printed visually appealing texture modified black fungus-based food as potential dysphagia diet, with addition of gums (0.3%, 0.6%, 0.9%, w/w), i.e. k-carrageenan gum (KG), xanthan gum (XG) and arabic gum (AG). Results indicated that KG and XG addition significantly increased the mechanical strength (yield stress and elasticity), viscosity, hardness and gumminess of ink samples by reducing water mobility and facilitating hydrogen bond formation, while AG addition showed an opposite effect. International dysphagia diet standardization initiative (IDDSI) tests indicated that AG and KG containing sample failed the spoon tilt test within IDDSI framework, while XG containing sample could be classified as level 5-minced and moist dysphagia diet. 3D printed samples using control or AG containing ink illustrated poor self-supporting capability. KG containing ink was not easy for extrusion with defective points in printed samples. In contrast, XG-0.9% samples demonstrated high printing precision with great self-supporting capability and smooth surface texture. This work provides insights for the development of visually appealing dysphagia diet using 3D printing.
Article
3D printing technology and its extension 4D printing technology have been extensively developed since it was proposed and applied to many industries, including aerospace, biomedical, and food fields. However, there are material limitations for 3D/4D food printing, as some natural food gels cannot be directly applied to 3D/4D food printing, and most natural food gels tend to have poor printing characteristics, which are difficult or impossible to print. Additives in food have a long history of application, which can change some properties of natural food gels. Suitable rheological property is the primary condition of 3D/4D food printing, most of the research is about improving the rheological property of ink, while the research on improving the thermal property, electrostatic property, nutritional property and sensory quality of ink (especially electrostatic property and nutritional property) is still insufficient. This article discusses the printing characteristics (rheological properties, thermal properties, electrostatic properties, nutritional properties, and sensory qualities) of natural food gels that are improved by additives in 3D/4D food printing, mainly from three types of additives: lipids, hydrocolloids, and carbohydrates.
Article
Background Gelling is an important way to texturizing, develop novel products, and carry bioactive compounds in the food industry. Some proteins and gums demonstrate gelling character. However, when they are mixed, the properties of the resulting gel may be improved even when some gums not gelling alone. There are many reviews in literature centered on protein-polysaccharide interactions and the use of such mixed systems as complexes. Although, the mixed gelation and particularly the effect of gum addition on the gel properties, have been scarcely approached. Scope and approach This review focused on the most used natural gums for food gelling purposes and their effect on the microstructure, rheological properties, and water retention capacity of mixed gels to serve as a guide for the design of gelling mixed systems. This insight can allow protein-gum-based gel properties to be tuned for specific food applications. Key Findings and Conclusions Gum addition to a protein system induces structural changes in the tridimensional red of the gel that can improve its rheological properties and water holding capacity depending on the structure, molecular weight, density, and nature of the charge of the biopolymers used. Additionally, pH, ionic strength, protein-gum ratio and concentration of the gum are critical factors during gel formation.
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The goal of this study was to investigate the viability of microencapsulated and coated Lactobacillus acidophilus in yogurt during storage in a refrigerator for 28 days and in simulated gastrointestinal conditions. Furthermore, the effect of the microencapsulated and coated L. acidophilus on the physicochemical, textural, and sensory properties of yogurt was assessed. Lactobacillus acidophilus was microencapsulated in sodium alginate and coated with xanthan and/or whey protein. The coating led to the increase in the microcapsule diameter and the microencapsulation yield, while it led to the decreased moisture and water activity (aw) of the microcapsule. The survival of L. acidophilus microcapsule coated with whey protein and xanthan in yogurt during storage and exposure to simulated gastrointestinal conditions was significantly increased. Compared with free bacteria, the L. acidophilus microcapsule coated with whey protein and xanthan had the increased viability in yogurt until 2.16 log CFU/g during storage and 3.52 log CFU/g in simulated gastrointestinal conditions. After the 28th day of storage, a significant difference between the acidity and pH of yogurt containing coated and microencapsulated L. acidophilus and control yogurt was not observed. However, yogurt containing free L. acidophilus had lower pH and higher acidity and showed a significant difference (p < .05) with other samples. Although the coating of L. acidophilus microcapsule did not affect the sensory properties and gumminess of yogurt, it increased the firmness, adhesiveness, and viscosity of this product and caused a significant decrease in syneresis and cohesiveness. In general, the application of whey protein and xanthan coating on L. acidophilus microcapsule surface could increase the viability of this probiotic in yogurt during storage and in simulated gastrointestinal conditions and improve the texture attributes of yogurt.
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In this study the heat induced synergistic gelation of different hydrocolloid solutions, xanthan gum types (XG) in mixture with galactomannans like guar gum (GG), locust bean gum (LBG) and konjac glucomannan (KGM) is investigated. The physical mechanism of the synergy in thickening and gelling of blends depends on the monomer structure, the molecular weight, the charge, the polarity, and the chain stiffness of the hydrocolloids. Particularly the properties of the electrically neutral galacto- and glucomannans mixed in combination with xanthan gum strongly affect the synergistic effects. These are influenced by the number and distribution of mannan side chains and thus their flexibility. While the pure components do not show gelation on their own, they form viscoelastic solutions or even gels when mixed together and heated. In this study, rheological properties of the resulting composite gels of 0.5% (w/w) were examined under different physicochemical and thermal conditions. Focus was laid on thermally induced gels, as these gels showed higher synergistic effects compared to the non-heated ones. The gelation mechanisms were investigated by strain and temperature dependent oscillatory rheological measurements. Blends with XG-GG (20:80) showed the weakest synergism, followed by XG-LBG blends (20:80), whereas XG-KGM (60:40) blends showed the highest increase of the storage modulus. This can be explained by different local interactions in combinations with the flexibility of the various components. Furthermore, the impact of monovalent salt on the interactions was investigated. Addition of sodium chloride at 0.05% and 0.5% (w/w) concentrations influenced the gelling due to Coulomb screening of the negative charges of XG. Consequently, the synergism, in particular the storage modulus, is strongly affected by variation in salt concentration. We propose specific models based on the gel formation in case of XG-LBG and XG-KGM blends, whereas XG-GG shows an entropic phase separation due to flexibility of GG.
Chapter
Tissue engineering combines cells, suitable physiochemical factors, materials, and engineering knowledge to replace or revamp living tissues. As an emerging field, it scavenges for newer materials and optimizes those for the application area. Natural polysaccharides like gellan gum, xanthan, and their nanocomposites have emerged as such biomaterials because they can mimic the native condition as well as having excellent biocompatibility. They have tunable mechanical, rheological, or swelling behavior. The gelling property of these composites allows the formation of a suitable hydrogel scaffold. Gellan and xanthan-based hydrogel scaffolds or 3D microstructures allow cell attachment, proliferation, differentiation, motility for proper tissue regeneration, or organ reconstruction. The extraction, processing, structure, and properties of gellan and xanthan gum are reviewed extensively in this chapter. Application of gellan and xanthan based materials in tissue engineering including bone, cartilage, intervertebral disc, retinal, neural, soft, skin, or other tissues are also described in detail. Summary tables for all of the applications and future trends are also attached for the reader’s convenience.
Article
The role of food hydrocolloids on the 3D printability of meat products is discussed by evaluating the key rheological properties of the meat paste or “ink” in each stage of the 3D printing process, namely extrusion, recovery, deposition, and post-processing. The effect of hydrocolloids on the yield stress, viscosity, shear-thinning behaviour, shear recovery, storage modulus, and loss tangent of different meat-based inks and its repercussion on the extrudability, filament characterization, shape fidelity and/or shape stability of the 3D printed meat products is assessed. Thickeners enhance the viscosity of the paste for ease of initial and continuous extrusion, and consistency of the printing result. Gelling agents contribute to the formation of viscoelastic systems with varying strength, beneficial for shape fidelity and stability. Therefore, understandings the solubility, heat resistance and stability of the hydrocolloids used is imperative for the post-processing feasibility of 3D printed meat products.
Article
Xanthan gum (XG) was modified by the twin-screw extrusion process in the presence of Octenyl succinate anhydrate (OSA) starch in this study. The impact of OSA starch level on the rheological properties of XG was investigated. The extrusion process significantly improved the dispersibility, pseudoplasticity and elastic modulus of XG. The solubility and viscosity of the extruded XG in aqueous solution (1.0%w/w) were increased from 67.04% to 0.2302 Pa s to 95.20% and 1.1676 Pa s, respectively, and reached the maximum of 96.63% and 1.7060 Pa s when OSA starch level was 10%. Extruded samples were more sensitive to temperature and salt ion. Meanwhile, the co-extrusion process significantly changed the rheological properties of XG in the solutions at different pH values and sugar concentrations. The analysis of FTIR and SEM observation revealed that the molecular chains of XG and OSA starch were entangled through hydrogen bonding after the extrusion processing, leading to the formation of a denser network structure. In general, the extruded XG exhibited a strong gelatinous property with a high pseudoplasticity, while its features of high viscosity and dispersibility have a great potential for the application in food industry, especially in dysphagia products.
Article
This work presents the use of xanthan gum (XG) to prepare protein-containing nanoparticles (NPs). A biocompatible methodology of electrostatic complexation at acidic pH and subsequent thermal treatment is applied using the protein bovine serum albumin (BSA). The NPs have well-defined size and molar mass and are stable upon increase of pH. The secondary conformation of BSA appears irreversibly changed upon thermal treatment within the complexes with XG. The NPs inherit the properties of BSA as they are found to have hydrophobic domains and pH-dependent surface charge. XG-BSA NPs are able to bind the nutraceutical substance curcumin (CUR) and protect its structure against degradation at neutral pH. This investigation introduces the employment of XG for the formulation of protein NPs as nanocarriers of bioactive compounds.
Article
This work investigates the quality of emulsions obtained from fast emulsification in a microsystem implemented at high throughput. The aim is to manufacture oil in water (O/W) emulsions in which bioactive ingredients could be encapsulated. These emulsions may be of interest for cosmetic, nutraceutical and/or pharmaceutical applications. A microsystem based on an improved cross-slot configuration is tested for production of emulsions with various formulations in a range of flow rate comprised in 100-600 mL/min. Dispersed lipid phase consists mainly in sunflower oil. The continuous aqueous phase is a Non-Newtonian fluid as it includes xanthan in order to stabilize the emulsions. Several commercial surfactants are also used to stabilize the emulsions. Their stability is examined during a storage period of approximately 30 days. For most tests, the evaluation of emulsions is based on a comparison with emulsions produced from a commercial laboratory rotor stator emulsifier. The results show only a few slight differences between the characteristics of emulsions generated in continuous in the microsystem and those obtained from the batch rotor-stator emulsifier. The results are therefore mostly comparable, which leads to the conclusion that microsystems can offer an interesting alternative to the small-scale production of emulsions.
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The printability and textural attributes of cooked beef pastes with xanthan gum (XG), guar gum (GG), k-carrageenan (KC), and locust bean gum (LB) added individually or as blends (50:50 ratios) in concentrations of 0.5% and 1% were analysed. Pastes with ease of extrusion displayed viscosities at rest ranging from 108±11 Pa.s to 350±26 Pa.s and viscosities at the estimated shear of extrusion (∼50/s) of about 4.3±0.1 Pa.s to 11.6±0.3 Pa.s. Samples with higher 3D printing dimensional deviation showed increasing phase angles across frequencies, reaching 21.3±0.8° and 23±1° and denoting less shape stability over time. In contrast, those with minimal or negligible deviation displayed either constant or decreased phase angles with values ranging between 13.2±0.2° and 17.4±0.7°. In addition, the textural attributes by Texture Profile Analysis (TPA) and the International Dysphagia Diet Standardisation Initiative (IDDSI) testing methods suggested the application of the different formulations as modified-texture foods, potentially categorising into levels 5, 6 and 7 of the IDDSI framework.
Article
Xanthan molecules possess an ordered helical conformation in a solution, and this conformation can be changed by varying the temperature. Currently, only very few studies have assessed the effect of the low temperatures on the conformation of xanthan. We determined the structure, interfacial properties, and hydrophobicity of xanthan at a low temperature using XRD, FTIR, pendent drop, and fluorescence spectroscopic analysis. Furthermore, we explored the conformational changes in xanthan using DLS, rheometer, and AFM. We found that the properties of xanthan had been changed at a low temperature compared to a xanthan sample at room temperature. Our results suggest that the portion of the double-helix in xanthan increases when the temperature is decreased; the molecules will aggregate after lyophilization, and then the properties, such as interfacial tension and hydrophobicity, will be changed.
Article
This study aims to explore the production and physicochemical properties of an exopolysaccharide (EPS) produced from soil isolate, Paenibacillus sp. ZX1905 in submerged culture. The highest EPS production of 15.67 g/L was achieved in a medium containing soluble starch, peptone and inorganic salts. The purified EPS exhibited excellent skin lubricating properties and was named lubcan. The chemical analysis reviewed that lubcan was an acidic heteropolysaccharide consisted of glucuronic acid, glucose, mannose, galactose, and rhamnose in a molar ratio of 2:3:1:2:2, and the average molecular mass was about 3.27 × 10⁶ Da. NMR and methylation analysis revealed that lubcan backbone was composed of 1,4-α-Man, 1,4,6-α-Glc, 1,3-α-Gal, 1,3-β-Rha, and 1,3-β-Gal, together with the branches of 1,3-α-Glc, 1,3-α-Rha, two 1,4-α-GlcA, and terminal-α-Glc(4,6-pyr). The lubcan solution exhibited stability at pH ranging from 5.0 to 7.0, temperature between 5 and 50 °C, and monovalent salts (0.2 M) and divalent salts (0.05 M) addition. The moisture absorption rates of lubcan were 16.98% and 40.41% under the conditions of 43% and 81% relative humidity, which were close to that of hyaluronic acid (17.28% and 41.20%, respectively). These properties make lubcan a good alternative to more expensive hyaluronic acid in the cosmetic industry.
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Encapsulation in alginate beads has always been limited by the leakage due to the too wide distribution of pore sizes. Mixing alginate with other polymers have sometimes reduced the problem. Hydrocolloids from seven tropical vegetal species (barks of Triumfetta cordifolia and Bridelia thermifolia, seeds of Irvingia gabonensis and Beilschmiedia obscura, and leaves of Ceratotheca sesamoides, Adansonia digitata and Corchorus olitorius) were screened for synergistic interactions with alginate in dilute aqueous solution. Mixtures with alginate were made at different volume proportions and deviations from the initial viscosity set at 1 were evaluated. In distilled water, the gums from T. cordifolia, B. obscura, C. sesamoides and C. olitorius presented synergies with alginate. In 2 mM calcium chloride, the seven gums showed positive synergy. Interactions are favored by gum flexibility and the presence of charges, although high charges reduced the interactions. Alginate fraction of maximum viscosity enhancement depends on the ability to conformational order of the gum. The measure by laser diffraction of alginate-gum particles sizes at different fractions showed that the cooperative interactions did not always involve the largest complexes formed in gums associations. The occurrence of these interactions predicts the formation of homogeneous mixed gels at higher polymer and calcium concentrations.
Article
We have isolated and characterized a water soluble polysaccharide from Cola millenii seeds. It was found to be composed of a total of 59% neutral sugars (mainly rhamnose, galactose and arabinose ~24, 13 and 8% respectively) and 41% uronic acids [mainly galacturonic acid]. The weight and number average molar mass values were found to be 4.7 × 10⁶ g/mol and 3.5 × 10⁶ g/mol, respectively. The polysaccharide exhibited polyelectrolyte properties with the intrinsic viscosity varying with salt concentration. The polysaccharide formed a highly viscous solution in water with apparent zero shear viscosities of 0.59–772 Pa·s at concentrations 0.3–2.5 wt%. The solutions were shear thinning even at very low concentrations. The mechanical spectra showed gel-like characteristics at concentrations >2 wt%. The rheological behavior indicates the polysaccharide has potential for application as a thickener and suspending agent in food, pharmaceutical and cosmetic formulations.
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In the present work the antiglaucoma drug, acetazolamide, was formulated as an ion induced nanoemulsion-based in situ gel for ocular delivery aiming a sustained drug release and an improved therapeutic efficacy. Different acetazolamide loaded nanoemulsion formulations were prepared using peanut oil, tween 80 and/or cremophor EL as surfactant in addition to transcutol P or propylene glycol as cosurfactant. Based on physicochemical characterization, the nanoemulsion formulation containing mixed surfactants and transcutol P was selected to be incorporated into ion induced in situ gelling systems composed of gellan gum alone and in combination with xanthan gum, HPMC or carbopol. The nanoemulsion based in situ gels showed a significantly sustained drug release in comparison to the nanoemulsion. Gellan/xanthan and gellan/HPMC possessed good stability at all studied temperatures, but gellan/carbopol showed partial drug precipitation upon storage and was therefore excluded from the study. Gellan/xanthan and gellan/HPMC showed higher therapeutic efficacy and more prolonged intraocular pressure lowering effect relative to that of commercial eye drops and oral tablet. Gellan/xanthan showed superiority over gellan/HPMC in all studied parameters and is thus considered as a promising mucoadhesive nanoemulsion-based ion induced in situ gelling formula for topical administration of acetazolamide.
Article
Xanthan gum is a viscous polysaccharide produced by fermentation of the bacterium Xanthomonas campestris. The efficient stabilization and suspension properties of xanthan are related to its structural features: high molecular weight and extended conformation. New studies have shown that the levels of acetate and pyruvate substituents can affect both structural and functional properties. Differential Scanning Calorimetry and Atomic Force Microscopy results show that low acetate xanthan gum adopts a less ordered, more flexible conformation. These conformational changes result in a novel product, which has enhanced functional properties, such as increased acid stability and enhanced interaction with galactomannans.
Conference Paper
Swallowing is a very complex neuromuscular process. Swallowing problems, known as dysphagia, result in difficulty getting food from the mouth to the stomach. There are many disorders that can cause dysphagia. These include neurological disorders, stroke, traumatic brain injury, Huntingdon's disease, multiple sclerosis, Parkinson's disease and cerebral palsy. Approximately 10 million Americans are evaluated writh swallowing difficulties every year and figures suggest that approximately 14% of those aged over 60 are affected by dyspahgia. Dysphagia is not directly associated with ageing but is a symptom of the degenerative diseases common in old age. The rheological properties of the bolus significantly influence the swallowing process and the use of hydrocolloids to control the rheology can greatly help in the management of the condition. In Japan, for example, hydrocolloid thickeners are used in a dry mix powder form for instant thickening of water, fruit juice or milk. The products are called TOROMI and arc used in hospitals and health care centres for the elderly. Creating instant viscosity under sub-optimal mixing conditions creates a number of challenges for the use of hydrocolloids in this application and the factors influencing their performance will be discussed.
Chapter
Abstract Xanthan exists in solution at moderate temperatures in a native, ordered conformation. At low salt levels this order may be melted out, as monitored by n.m.r. relaxation, optical rotation, circular dichroism, and intrinsic viscosity. We suggest that in the ordered conformation the charged trisaccharide sidechains fold back around the cellulose backbone, to give a rigid, rod-like structure. Increasing salt concentration stabilises this conformation by minimising electrostatic repulsions between the sidechains. At the salt levels encountered in most industrial situations, the ordered form is stable to above 100°C, hence the relative insensitivity of xanthan solution viscosity to temperature or further increase in ionic strength. Stacking of the rigid molecules in solution builds up a tenuous intermolecular network, giving rise to the other commercially attractive properties, such as suspending ability, emulsion stabilisation, and thixotropy.
Article
Aqueous solutions of low-molecular-weight sodium xanthan with a degree of pyruvation of about were heated at 95°C for different time periods td between 2·5 and 15 h, mixed with aqueous sodium chloride to an NaCl concentration of 0·01 or 0·1 m and subjected to viscosity, optical rotation and sedimentation equilibrium measurements at 25°C. The measured specific rotations showed that, upon addition of aqueous NaCl to 0·1 m, Na xanthan disordered in water at 95°C became ordered to a conformation locally similar to that of each chain in the double helix of the polysaccharide in 0·1 m aqueous NaCl at 25°C. However, both viscosity and molecular weight decreased considerably below the values for the double-helical dimer as td increased. No substantial degradation of the sample was found to occur within td = 9 h. It was concluded from data analysis that at least 70% of the dimers dissociated into monomers when pure water solutions were heated at 95°C for 9 h.
Article
A range of xanthans (Na+ salt form) with varying levels of acetyl and pyruvic acid substitution were prepared by culturing different strains of Xanthomonas campestris and by chemical deacetylation and depyruvylation. Oscillatory-shear measurements were used to characterize the behaviour of xanthan and guar gum alone, and of mixtures of the two in de-ionized water — the xanthan under these conditions was largely in the disordered form. The mechanical spectra of the blends resembled an ‘entanglement network’ system and showed some features characteristic of the individual components. However, evidence from both rheological and chiroptical measurements indicated a possible weak interaction between some low-acetyl xanthans and guar.
Article
The exocellular polysaccharide fermented from glucose in good yield by Xanthomonas campestrìs NRRL B-1459, has been characterized. The general aspects of chemical constitution have been established, as well as the physical properties related to practical applicability. This macromolecular polysaccharide is composed of D-mannose, D-glucose, D-glucuronic acid (as the potassium salt), and a small proportion of acetyl groups. It can be produced on an industrial scale and is stable is storage. Analytical fractionation indicates fairly sharp molecular distribution for the native polysaccharide. The polysaccharide forms homogeneous dispersions in water which show plastic rheological properties and viscosity comparable with that of high-grade plant gums. Outstanding characteristics of practical significance are the atypical insensitivity of solution viscosity to salt effects and to heat, especially when salt is present. Solutions of low concentration show a restricted viscosity decrease upon salt addition; those of higher concentrations show substantial increases. Viscosity is enhanced still further by monovalent cations at basic pH and by divalent cations at neutral or slightly basic pH. Salt moderates or eliminates any viscosity decrease due to heat and, in somewhat higher concentrations, it increases the viscosity of heated solutions. Heating or deacetylating Polysaccharide B-1459 causes no impairment of its properties, but actual improvement. The constitutional basis for these unusual properties is discussed.
Article
A range of xanthans (Na+ salt form) with varying levels of acetyl and pyruvic acid substitution were prepared by culturing different strains of Xanthomonas campestris and by chemical deacetylation and depyruvylation. Oscillatory-shear measurements were used to characterize the interaction between these polymers and locust bean gum (LBG) in de-ionized water and the data were analysed statistically. The majority of the polymers interacted to form a strong thermoreversible-gel network, and the strength of the system was shown to be heavily dependent on the level of acetyl substitution. A polymer from a mutant strain of X. campestris, believed to lack the terminal mannose residue from the trisaccharide side-chains, formed an exceptionally weak gel network, suggesting that the xanthan side-chain may play an important role in the interaction with LBG.
Article
Xanthan gum, the extracellular polysaccharide from Xanthomonas campestris, has been reinvestigated by methylation analysis, and by uronic acid degradation followed by oxidation and elimination of the oxidized residue. The polysaccharide is composed of pentasaccharide repeating-units with the following structure:
Article
Partial, acid hydrolysis of the extracellular polysaccharide from Xanthomonas campestris gave products that were identified as cellobiose, 2-O-(β-d-glucopyranosyluronic acid)-d-mannose, O(β-d-glucopyranosyluronic acid)-(1→2)-O-α-d-mannopyranosyl-(1→3)-d-glucose, O-(β-d-glucopyranosyluronic acid)-(1→2)-O-α-d-mannopyranosyl-(1→3)-[O-β-d-glucopyranosyl-(1→4)]-d-glucose, and O-(β-d-glucopyranosyluronic acid)-(1→2)-O-α-d-mannopyranosyl-(1→3)-[O-β-d-glucopyranosyl-(1→4)-O-β-d-glucopyranosyl-(1→4)-d-glucose. This and other evidence supports the following polysaccharide structure (1) which has been proposed independently by Jansson, Kenne, and Lindberg:
Article
Semi-dilute (ca 2 g/dl) aqueous xanthan (mean molar mass ca 1 x 10(6) g/mol), when heated in the presence of 0.1 M NaCl to a temperature above the order<-->disorder transition temperature, forms highly viscoelastic solutions when returned to room temperature. The steady shear and dynamic rheological behaviour of these solutions discloses a weak gel structure, the viscosity of which is unusually sensitive to the rate of shear. In shear thinning behaviour these heat and salt treated xanthan solutions mimic the properties of the aqueous hyaluronic acid solutions widely used in viscosurgical techniques. The double stranded model of native xanthan is invoked to interpret the observed behaviour of heat and salt treated semi-dilute aqueous xanthan.
Genetics and biochemistry of xanthan gum production by Xanthomonas campestris Food Biotechnology Microorgan-isms
  • N E Harding
  • L Ielpi
  • J M Cleary
Harding, N.E., Ielpi, L. and Cleary, J.M. (1995) Genetics and biochemistry of xanthan gum production by Xanthomonas campestris. In: Y.H. Hui and G.C. Khachatourians (eds), Food Biotechnology Microorgan-isms. VCH Publishers, New York, pp. 495–514.
Char Count= 342 Food Stabilisers
  • K P Sutherland
  • I W Ross-Murphy
  • S B Dea
BLBK202-Imeson September 1, 2009 11:3 Char Count= 342 Food Stabilisers, Thickeners and Gelling Agents Shatwell, K.P., Sutherland, I.W., Ross-Murphy, S.B. and Dea, I.C.M. (1991a) Influence of the acetyl sub-stituent on the interaction of xanthan with plant polysaccharides – I.
Influence of the acetyl sub-stituent on the interaction of xanthan with
  • K P Shatwell
  • I W Sutherland
  • S B Ross-Murphy
  • I C M Dea
Shatwell, K.P., Sutherland, I.W., Ross-Murphy, S.B. and Dea, I.C.M. (1991b) Influence of the acetyl sub-stituent on the interaction of xanthan with plant polysaccharides – II.