Studying the Interaction of Xanthan Gum and Pectin with Some Functional Carbohydrates on the Rheological Attributes of a Low-Fat Spread

Effects of xanthan gum (XG) (0.1 wt%) and pectin (PE) (0.5 wt%) alone and in combination with different concentrations (0.2 and 0.4 wt%) of locust bean gum (LBG), modified starch (MS), and Na-alginate (ALG) on some of the rheological characteristics of low-fat spreads, including flow behavior curves, rheological modeling, apparent viscosity, rheological modules (storage modulus (G′) and loss modulus (G″)), and delta degree (G″/G′) were studied. Results showed the power-law model was better than the Herschel–Bulkley model to describe the flow curve of dispersions. The k-value in the power-law model increased with increase in biopolymers concentration in solution. All samples exhibited shear-thinning flow behavior with a low yield stress. Dynamic oscillatory shear test showed that the spreads had a viscoelastic solid behavior with a gel-like structure. The G′ value was increased by increasing frequency from 0.03 to 15 Hz, while the G″ and G″/G′ values decreased. Also, MS in combination with XG and PE led to increase the G′ values of spreads in comparison with ALG and LBG. Moreover, microstructural and stability observations revealed that the spreads prepared with 0.1% XG-0.2% LBG significantly had the highest oiling out.     

Rheological properties of water-soluble cross-linked xanthan gum

Water-soluble crossslinked xanthan gum (CXG) was prepared from xanthan gum (XG) and epichlorohydrin under alkaline condition by ethanol solvent method. Rheological properties and heat resistance performance of different concentrations of aqueous XG and CXG solutions were investigated. The results showed that the apparent viscosity of 4 g · L^?1 CXG solution was 2.57 times that of 4 g · L^?1 XG solution. The storage modulus G′ and the loss modulus G″ of CXG solutions were greater than those of XG solutions, and viscoelastic and thixotropic properties were more significant in CXG solutions. At 80°C, these two solutions were sheared at 170 s^?1 for 90 minutes, the reserved viscosity was 32.30 and 62.15 mPa · s for XG and CXG solutions, respectively. The heat resistance performance of CXG solution was better than that of XG solution. Nonlinear co-rotational Jeffreys model could be applied to describe the flow curves of XG and CXG solutions correctly, and the calculated values were in good agreement with the experimental data.     

Rheological and microrheological characterization of a novel amphoteric xanthan gum

A novel amphoteric xanthan gum (AXG) containing anionic carboxyl groups and cationic quaternary ammonium substituents was prepared from xanthan gum (XG) and 3-chloro-2-hydroxypropyltriethanolammonium acetate. The rheological and microrheological properties of AXG and XG solutions were studied in this work. The rheological results showed that the apparent viscosity of the 0.4% AXG solution was 5.26 times that of the 0.4% XG solution, and the AXG solution exhibited more obvious thixotropy and much stronger viscoelasticity than the XG solution. Both experiment and numerical simulations were adopted to investigate the gel-breaking process of the AXG solution, and the rheokinetics equations can well describe the evolution of complex viscosity. Moreover, the optical microrheology method was also adopted to investigate the microrheological behavior of AXG and XG solutions. The microrheological results showed that the AXG solution exhibited higher viscosity index at zero shear and a more obvious solid-like behavior than the XG solution. Good agreement is found when comparing the results obtained from microrheology to classical rheology, which verifies the feasibility of the microrheology method for measuring the solution properties, especially some properties not well described by the current rheological approach.     

The rheological and thickening properties of cationic xanthan gum

In the present study, cationic xanthan gum (CXG) was synthesized to enhance the rheological property of xanthan gum (XG) by attaching quaternary amine groups to the backbone of XG. The efficacy of the substitution was confirmed by FT-IR spectra and ¹³C NMR. The surface morphology was changed considerably as demonstrated by SEM. The examined rheological properties of XG and CXG include steady-state and dynamic rheological properties. The results show that quaternary amine groups are successfully grafted onto the XG molecule. Apparent viscosity, storage modulus, and loss modulus of CXG solutions are greater than those of XG solutions under the same conditions. It is moreover found that apparent viscosity and viscoelasticity increase with the degree of substitution. The data indicate that the modified XG has much better heat resistance.     

Thermal studies on the starch-g-copolymers prepared from two terpene acrylate monomers under oxidative conditions

The simultaneous thermal studies (TG/DTG/DSC) coupled with the FTIR analysis of the gaseous decomposition products created under oxidative heating of starch-g-poly(neryl acrylate) and starch-g-poly(geranyl acrylate) copolymers have been presented. To these studies, the copolymers with the following grafting percents (G) were selected: starch-g-poly(neryl acrylate) copolymers: 36.6?±?0.3%, 40.3?±?0.4%, 42.8?±?0.4% and starch-g-poly(geranyl acrylate) copolymers: 28.9?±?0.2%, 32.4?±?0.6%, 35.6?±?0.4%. The performed tests proved that the thermal resistance of the copolymers was strongly dependent on their G values, despite a small difference in the G values between the samples. The slight increase (ca. 6.2–6.7%) in the G value caused the significant drop of the thermal stability of all the studied materials. The TG/DTG/DSC studies confirmed at least three-stage decomposition mechanism of the copolymers where simultaneous pyrolysis, oxidation, dehydration and decarboxylation processes took place. The TG/FTIR analyses showed the emission of various structure fragments; among them, one can mention the creation of some organic fragments such as aldehyde, acid, alkene, alkane, furan fragments, CH₄ and inorganic species (CO₂, CO, H₂O) as a result of the oxidative decomposition processes of the studied copolymers. In addition, the conducted studies demonstrated similar decomposition course and mechanism for both types of the copolymers, regardless of the monomer type used to the graft process.

     

Wettability of commercial starches and galactomannans

This paper describes the wettability of basic commercial polysaccharides: starches (potato PS, wheat WS, corn CS, tapioca TS, kuzu KS) and galactomannans (fenugreek gum FG, guar gum GG, tara gum TG, locust bean gum LBG). The study was conducted using the Washburn capillary rise method and thermal drying. This allowed one to determine the material constant C, contact angle θ, surface free energy of solid SFE, and initial moisture content M. The measured values of contact angle θ and surface free energy SFE indicated that potato starch (70.9°, 41.1?mN?·?m^?1) and wheat starch (88.4°, 30.2?mN?·?m^?1) were characterized by the highest and lowest wettability among the examined starches, respectively. In turn, the galactomannans were poorly wettable substances. Their contact angles θ were approximately equal to 90°, showing a slight increase with increasing substitution degree. The observed decrease in surface free energy SFE from 30 to 29.6?mN?·?m^?1 indicated a very minor hydrophobization of their surfaces. Material constant C was practically independent of temperature, and an increase in initial moisture content M in the examined starches and galactomannans proceeded according to the following schemes: CS?相似文献   

Preparation and Performance of Thickened Liquids for Patients with Konjac Glucomannan-Mediated Dysphagia

The present study sought to characterize the rheological and thickening properties of Konjac glucomannan (KGM) and prepare thickening components for special medical purposes using KGM and maltodextrin as the primary raw materials and guar gum (GG), xanthan gum (XG), locust bean gum (LBG), and carrageenan (KC) as the supplemented materials. The formulation and preparation processes were optimized through single factor experiments taking sensory evaluation as an indicator. The results confirm that KGM had excellent thickening performance, reaching about 90 times its own mass. The optimal formulation process of the thickening components based on KGM was as follows: the mass concentration of the compound thickener (KGM/GG/XG/LBG/KC = 13:2:2:2:1) was 5.0–7.0 mg/mL; the maltodextrin concentration was 10.0 mg/mL; the brewing temperature of the thickening component was 60 °C with no restriction on consumption time. The rheology test results revealed that the thickening components had shear thinning characteristics, which could provide three different thickening effects of nectar-thick level (350 mPa·s), honey-thick level (1250 mPa·s), and pudding-thick level (1810 mPa·s) suitable for people with different degrees of chewing disorders. Overall, this study provides a theoretical basis and technical reference for KGM as a dietary nutrition support for patients with dysphagia.     

The influence of variant PE‐b‐PEO segments on physical properties of LLDPE graft copolymers

A method was adopted to fix a series of polymers of PE‐b‐PEO with different PEO/PE segments on the chains of LLDPE. Maleic anhydride (MA) reacting with hydroxyl group of PE‐b‐PEO (mPE‐b‐PEO) was used as the intermediate. The structures of intermediates and graft copolymers were approved by ¹H NMR and FTIR. XPS analysis revealed a great amount of oxygen on the surface of grafted copolymers although the end group of PEO was fixed on the LLDPE chains through MA. Thermal properties of the graft copolymers as determined by differential scanning calorimetry (DSC) showed that PE segments in the grafted monomers could promote the heterogeneous nucleation of the polymer, increase T_c, and crystal growth rate. While the amorphous PEO segments which attached to the crystalline PE segments in LLDPE, impaired their ability to fit the crystal lattice, and depressed the crystallization of LLDPE backbones. In this study, it was also verified through the dynamic rheological data that increasing M_n of grafted monomers significantly increased the complex viscosity and enhanced the shear‐thinning behavior. Long‐branched chains formed by grafted monomers enhanced the complex moduli (G′ and G″) value and retarded relaxation rate. However, there were little influence on the rheological properties when increasing the amounts of PEO segments (or decreasing PE segments) of grafted monomers with similar molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 506–515, 2008     

Rheological behavior of polypropylene/octavinyl polyhedral oligomeric silsesquioxane composites

The reactive blending composites of isotactic polypropylene (PP)/octavinyl polyhedral oligomeric silsesquioxane (POSS) were prepared in the presence of dicumyl peroxide. Comparison of the rheological behavior of physical and reactive blending composites was made by oscillatory rheological measurements. It was found that the viscosity of physical blending composites drops at lower POSS content (0.5–1 wt %) and thereafter increases with increasing POSS content; that of reactive blending composites increases with increasing POSS content and displays a solid‐like rheological behavior at low frequency region when POSS content is higher than 1 wt %. The deviation of reactive blending composites from the scaling log G′–log G″ of linear polymer in Han plot, upturning at high viscosity in Cole–Cole plot, and from van Gurp–Palmen plot are related to the gelation behavior reactively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 526–533, 2008     

Rheological and electrical analysis in carbon nanofiber reinforced polypropylene composites

Two different types of carbon nanofibers (CNF) were incorporated in the same polypropylene (PP) matrix by twin‐screw extrusion. The electrical characterization of both CNFs/PP composites as a function of volume fraction show different electrical performance: conducting and nonconducting. The objective of this work is to study the rheological behavior of both composites with the aim of relating it to the electrical behavior. The results indicate that the rheological behaviors are different, suggesting that rheology differentiates the microstructural variations responsible for the electrical performance. Furthermore, the main rheological parameters were correlated to the electrical conductivity. The results show that G′/G″ and G′ are the most sensitive parameters when compared with the onset of electrical percolation. Finally, in spite of the intrinsic measuring differences between electrical and rheological analysis, the two calculated thresholds are very similar: ～0.5 for the rheological and ～0.4 for the electrical. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Rheology of (±)‐camphor‐10‐sulfonic acid doped polyaniline‐m‐cresol conducting gel nanocomposites

The rheological behavior of polyaniline‐(±champhor‐10‐sulfonic acid)_0.5‐m‐cresol [PANI‐CSA_0.5‐m‐cresol] gel nanocomposites (GNCs) with Na‐montmorillonite clay (intercalated tactoids) is studied. The shear viscosity exhibits Newtonian behavior for low shear rate (<2 × 10^?4 s^?1) and power law variation for higher shear rate. The zero shear viscosity (η₀) and the characteristic time (λ) increase but the power law index (n) decrease with increase in clay concentration. In the GNCs storage modulus (G′) and loss modulus (G″) are invariant with frequency in contrast to the pure gel. The G′ and G′ exhibit the gel behavior of the GNCs up to 105 °C in contrast to the melting for the pure gel at 75.7 °C. The percent increase of G′ of GNCs increases dramatically (619% in GNC‐5) with increasing clay concentration. The conductivity values are 10.5, 5.65, 5.51, and 4.75 S/cm for pure gel, GNC‐1, GNC‐3, and GNC‐5, respectively, promising their possible use in soft sensing devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 28–40, 2008     

黄原胶和瓜尔胶混合溶液及其硼砂交联体系的流变性能

本文研究了黄原胶(XG)和瓜尔胶(GG)的混合溶液及其硼砂(B)交联体系的流变性,考察了XG/GG间的“协同增效作用”以及溶液组成、pH和电解质(NaCl和CaCl 2)对其流变性的影响。结果表明,所有溶液体系均为假塑型流体,其流变曲线可用Herschel-Bulkley和Casson模型描述。XG和GG复配具有明显的“协同增粘效应”,在XG占两聚合物的质量分数w(XG)为20%和90%时协同增粘效应最强,其“协同增粘率”(R m)分别约为42%和34%。硼砂(B)可交联XG/GG混合溶液,其交联增粘效果随w(XG)的减小和硼砂质量浓度ρ(B)的增大而增大;在w(XG)=50%和ρ(B)=1.00 g/L时,“交联增粘率”可达85%。在所研究的pH值范围(6.2~10.0)内,XG/GG混合溶液的流变性基本无变化,而XG/GG/B交联体系(w(XG)=50%和ρ(B)=0.75~1.00 g/L)的表观粘度随pH值增大先升高后降低,pH=9.0时出现最大值,交联增粘率达107%。电解质可使XG/GG/B交联溶液(w(XG)=10%和ρ(B)=0.50 g/L)体系的粘度大幅下降,且CaCl 2的影响明显高于NaCl,表明交联结构的耐盐能力较差。这些结果加深了对XG/GG混合溶液流变性的认识,可为其实际应用(如在强化采油中的应用)提供依据。     

Synthesis of MgAl2O4 Spinel Nanometer Powder via Biology Polysaccharide Assisted Sol-Gel Process

A novel and cost-effective sol-gel process for preparation of MgAl₂O₄ spinel nanometer powders has been developed in this study. A solution of magnesium and aluminum nitrates in stoichiometric proportion was successfully embraced in the biology polysaccharide gel network, formed by the synergistic interaction between xanthan gum (XG) and locust bean gum (LBG) utilizing their broad-spectrum stability of salt tolerance and character of transformation from sol to gel on the condition of proper temperature and relative proportion of polymeric components. Dry gel could be obtained by vacuum dehydration of aqueous gel at low temperatures. Monolithic MgAl₂O₄ spinel nanometer powders were produced by calcining the dry gel above 800°C, with average crystallite size of 20 nanometers.     

Phase formation and transition in a xanthan gum/H2O/H3PO4 tertiary system

Phase formation and transition in a xanthan gum (XG)/H₂O/H₃PO₄ tertiary system were characterized by polarized optical microscopy, light transmission detection and rheological methods. Three distinct phases and a transition region—the completely separated (S) phase, the liquid crystalline (LC) miscible phase, the isotropically (I) miscible phase and the S plus LC region—were identified. The presence of H₃PO₄ in the XG/H₂O system inhibited the evolution of both the S and LC phases. The S and LC phases contained less than 73 and 62 wt% of H₃PO₄, respectively. As the temperature increased over 65 °C, the LC phase in the H₃PO₄-rich and H₂O-poor region seriously shrunk owing to the breakup of hydrogen bonds among the XG helical structure. At the same XG loading, the viscosity of the XG solutions in LC phase was found to be much higher than that in I phase. It indicated the existence of numerous XG intermolecular interactions in the LC phase that suppress the movement of liquid. A study of the kinetics demonstrated that the shrinkage relaxation time (τ) depended strongly on temperature and was fitted by the Volgel-Fulcher-Tammann (VFT) expression. The potential energy barrier of this liquid was quite low at approximately 3.0 kJ mol^?1, falling in the range of hydrogen-bond disassociation. The light absorbance test in heating mode revealed a biphasic transitional region between the LC phase and I phase. The contour of this region depended on the heating rate, and this fact was explained again by the relaxation behavior of XG helices at temperatures higher than 65 °C.     

Dynamic mechanical behavior of poly(vinyl-methyl ether)-poly(styrene) blends

The dynamic mechanical behavior of 10 and 20% poly(vinyl methyl ether)-polystyrene blends has been studied in the frequency range 10^?5 Hz to 5 Hz and temperature range 100–450 K. Isochronal plots of modulus G′ and loss factor, tan ?, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process at intermediate temperatures but below T_g may be inferred from the breadth of the G″ frequency curves in the transition zone of both blends. This process, at 280 < T < 300 K, is independent of PVME concentration and seems to be associated with the local modes of motions of PS chains. The rheological behavior of the blends shows them to be compatible up to 20% PVME. Their G′ and G″ data cannot be shifted along a frequency axis to produce a satisfactory master curve. The departure from thermorheological simplicity is much more clearly observed in the tan ? than in the modulus-frequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near T_g. A molecular model of the growth of microshear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior.     

The anionic glycan from the cactus cereus peruvianus

The columnar cactusCereus peruvianus provides various compounds of interest that account for most of its 10% dry wt content. Included are acidic gum and cellulose as the highly polymerized carbohydrate components, and a complex waxy lipid fraction. The major gum fraction (1.5 g% of the fresh phytobiomass on single aqueous extraction) is an uronylated rhamnoarabinogalactan whose intrinsic viscosity may exceed 1000 mL/g. Its rheological behavior is, in part, influenced by the nativeo-acetyl and cation components, mainly Ca²⁺. A pigment-free powdered gum was obtained by precipitating and washing the fresh mucilage with 2–3 vol of ethanol. The almost protein-free polysaccharide forms viscous solution upon redissolution. The possible uses to be investigated for the pretreated cactus gum will be as an adjuvant in the flocculation of water impurities and in formulation of cosmetics.

     

Determination of locust bean gum and guar gum by polymerase chain reaction and restriction fragment length polymorphism analysis

A polymerase chain reaction (PCR) was developed to differentiate the thickening agents locust bean gum (LBG) and the cheaper guar gum in finished food products. Universal primers for amplification of the intergenic spacer region between trnL 3' (UAA) exon and trnF (GAA) gene in the chloroplast (cp) genome and subsequent restriction analysis were applied to differentiate guar gum and LBG. The presence of <5% (w/w) guar gum powder added to LBG powder was detectable. Based on data obtained from sequencing this intergenic spacer region, a second PCR method for the specific detection of guar gum DNA was also developed. This assay detected guar gum powder in LBG in amounts as low as 1% (w/w). Both methods successfully detected guar gum and/or LBG in ice cream stabilizers and in foodstuffs, such as dairy products, ice cream, dry seasoning mixes, a finished roasting sauce, and a fruit jelly product, but not in products with highly degraded DNA, such as tomato ketchup and sterilized chocolate cream. Both methods detected guar gum and LBG in ice cream and fresh cheese at levels <0.1%.     

Viscoelastic properties of decrosslinked irradiation‐crosslinked polyethylenes in supercritical methanol

The viscoelastic properties of decrosslinked irradiation‐crosslinked polyethylenes using a supercritical methanol were investigated via oscillatory dynamic shear measurements. Decrosslinked polymers at a low reaction temperature exhibited solid‐like rheological properties, as evidenced by a small slope at G′ and G″, a long relaxation time, slow stress relaxation behavior, and considerable yield stress. In contrast, decrosslinked polymers at a high temperature exhibited liquid‐like rheological properties that included a large slope in G′ and G″, a short relaxation time, fast stress relaxation behavior, and nonyield stress. The difference in the viscoelastic properties of the decrosslinked polyethylenes was attributed to the difference in the gel content with the reaction temperature. A higher gel content induced stronger solid‐like viscoelastic properties. Hence, the rheological measurements were useful for analyzing the molecular structure of decrosslinked polymers using a supercritical fluid. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1265–1270, 2010     

三偏磷酸钠交联黄原胶的制备及其溶液流变性

以三偏磷酸钠(STMP)为交联剂,合成了水溶性低交联度黄原胶(XG),依据其溶液粘度优化出了最佳合成条件;考察了电解质质量分数、pH值及温度对STMP交联黄原胶(简记为SP-c-XG)溶液流变性的影响,并与XG溶液进行了对比。 结果表明,在所研究的电解质(NaCl和CaCl₂)质量分数(0~5.0%)、pH值(2~11)和温度(20~70 ℃)范围内,SP-c-XG和XG溶液的流变曲线均为假塑型,符合Herschel-Bulkley模型;其屈服值、表观粘度和动力学模量随电解质质量分数增大均先下降后上升,而随pH值的升高先升高后降低,随温度升高而降低。 SP-c-XG和XG溶液具有相似的流变性,但与XG溶液相比,SP-c-XG溶液具有更高的屈服值和表观粘度,特别是具有更强的弹性和耐温性,在油田强化采油领域具有重要应用前景。     

A New Strong-Acid Free Route to Produce Xanthan Gum-PANI Composite Scaffold Supporting Bioelectricity

Conductive hybrid xanthan gum (XG)–polyaniline (PANI) biocomposites forming 3D structures able to mimic electrical biological functions are synthesized by a strong-acid free medium. In situ aniline oxidative chemical polymerizations are performed in XG water dispersions to produce stable XG–PANI pseudoplastic fluids. XG–PANI composites with 3D architectures are obtained by subsequent freeze-drying processes. The morphological investigation highlights the formation of porous structures; UV–vis and Raman spectroscopy characterizations assess the chemical structure of the produced composites. I–V measurements evidence electrical conductivity of the samples, while electrochemical analyses point out their capability to respond to electric stimuli with electron and ion exchanges in physiological-like environment. Trial tests on prostate cancer cells evaluate biocompatibility of the XG–PANI composite. Obtained results demonstrate that a strong acid-free route produces an electrically conductive and electrochemically active XG–PANI polymer composite. The investigation of charge transport and transfer, as well as of biocompatibility properties of composite materials produced in aqueous environments, brings new perspective for exploitation of such materials in biomedical applications. In particular, the developed strategy can be used to realize biomaterials working as scaffolds that require electrical stimulations for inducing cell growth and communication or for biosignals monitoring and analysis.