Rheological characterization of functional walnut oil-enriched butters stabilized by the various polysaccharides

Dynamic rheological measurements provide a valid determination of the ability of polymeric ingredients to compensate the reduced contribution of fat to texture and mouthfeel, as well as provide an emulsion that easily breaks down in commercial low-fat butters. In this study, the linear effects of pectin (PE, 0.5%) and xanthan gum (XG, 0.1%) and their interactions with locust bean gum (LBG, 0.2% and 0.4%), sodium-alginate (ALG, 0.2% and 0.4%), and modified starch (MS, 0.2% and 0.4%) on the flow behavior, dynamic rheological characteristics, and stability of reduced-fat butters containing 10% walnut oil (WO) were investigated. Results showed that the power law model can adequately fit the shear-rate/shear-stress data (0.888?≤?r?≤?0.992, p?G′?>?G″ at all frequencies. The samples prepared with PE–LBG (0.2% and 0.4%) and XG–ALG (0.4%) had the highest G′ values. The phase angle (G″/G′) decreased with increasing frequency from 0.03 to 15?Hz. The maximum apparent viscosity and stability were, respectively, found for WO butters formulated with XG–0.2% ALG and PE–0.4% LBG.     

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.     

Lyotropic Liquid Crystal Formed in Oleyl Polyoxyethylene Solutions by Adding Different Additives: NaDC,Tween 80, Alkyl Esters

Lyotropic liquid crystalline of oleylpolyoxyethylene(20)(AEO₂₀)/oil/water system was investigated at 25°C. The phase behavior, microstructure, and rheological properties of liquid crystalline were investigated by rheological techniques and polarizingoptical microscopy in the presence of various additives including Tween 80, sodium deoxycholate (NaDC), isoamylacetate, butyl acetate, isopropyl myristate. Diagrams show that cubic phase transforms to hexagonal phase when a shorter chain length oil is applied or NaDC or Tween 80 is added to the system.Flow experiments indicate the shear-thinning properties and a plastic behavior. The turning points of flow curves of the system AEO₂₀ and system AEO₂₀/NaDC were found. The dynamic modulus increase with increase in water content however the tendency is weaken by adding NaDC. Frequency dependence of experimental G ′ and G ′ were fitted using the multiple Maxwell model the cubic LLCs described by three relaxation times while hexagonal LLCs described by 5–8 elements. When AEO₂₀ mixes with Tween 80, the hexagonal have a monotonic decrease distribution of relaxation times without valleys.     

Experimental Study and Numerical Modeling of Rheological and Flow Behavior of Xanthan Gum Solutions Using Artificial Neural Network

This study investigated effect of temperature, concentration, and shear rate on rheological properties of xanthan gum aqueous solutions using a Couette viscometer at temperatures between 25°C and 55°C and concentrations of 0.25 wt% to 1.0 wt%. The Herschel–Bulkley model described very well the non-Newtonian behavior of xanthan gum solutions. Shear rate, temperature, and concentration affected apparent viscosity and an equation was proposed for the temperature and concentration effect valid for each shear rate. This article also presents an artificial neural network (ANN) model to predict apparent viscosity. Based on statistical analysis, the ANN method estimated viscosity with high accuracy and low error.     

Modeling and Scaling of Food Dispersions

Scaling laws, determined by dimensional analysis, have been used to make experimental predictions of constitutive shear-flow rheology. This study aimed to scale and model the flow curves of various suspensions consisting of xanthan gum (0.5, 1 wt%) and WPI (2, 4 wt%), and to determine the best-scaling law and rheological model. The scaling methods were relative viscosity, Péclet number, and Reynolds number. When the apparent viscosity is reduced relative to the viscosity of the medium at zero-shear rate, a distinct reduced flow curve is obtained, regardless of xanthan and WPI concentrations. This study tough to develop a technique of simplifying complex non-Newtonian flow curves and, therefore, predicting the rheological flow curves and fluid mechanics when different modifiers are added to food suspensions. The flow behavior of all samples was successfully modeled with the power law, Ellis, and Cross models; the power law model best described the flow behavior of dispersions. Results showed that both G′ and G″ increased with xanthan and WPI. However, viscoelastic behavior was mainly governed by the xanthan gum content.     

Prediction of Rheological Properties of Multi-Component Dispersions by Using Artificial Neural Networks

This article shows the ability of artificial neural network (ANN) technology for predicting the correlation between rheological properties of multi-component food model systems and their chemical compositions. Multi-component food model systems were made of whey protein isolate (WPI) (2, 4 wt%), Iranian tragacanth gum (TG) (Astragalus gossypinus) (0.5, 1 wt%) and oleic acid (5, 10% v/v). The input parameters of the neural networks (NN) were these chemical compositions, namely WPI and TG concentrations, and oleic acid volume fractions. The output parameters of the NN models were rheological properties of multi-component food model systems (flow and consistency indices, viscosity, loss and storage moduli). Results showed that, ANN with training algorithm of back propagation (BP) was the best one for the creation of nonlinear mapping between input and output parameters. The best topology was 3-10-5. The ANN model predicted the rheological properties of multi-component food model systems with average RMSE 4.529 and average MAE 3.018. These results show that the ANN can potentially be used to estimate rheological parameters of multi-component food model systems from chemical composition. This development may have significant potential to improve product quality control and reduce time and costs by minimizing the rheological experiments.     

Physical and Rheological Characteristics of Emulsion Model Structures Containing Iranian Tragacanth Gum and Oleic Acid

The physical and rheological properties of oil in water model emulsion systems containing Iranian tragacanth gum (TG) (0.5, 1 g/100 ml emulsions), whey protein isolate (WPI) (2, 4 g/100 ml emulsions), and oleic acid (5, 10 ml/100 ml emulsions) were investigated for droplet-size distribution, creaming index, and rheological properties of emulsions. The shear-thinning behavior of all dispersions was modeled using power law, Cross, and Ellis models. The power law model described the flow behavior of dispersions for its lowest standard error (0.29) and highest determination coefficient (R²) (0.99). Rheological investigation showed that both loss (G″) and storage (G′) modules increased as gum and oil content increased. Delta degree was 0.1 and increased as frequency increased, indicating that liquid-like viscose behavior dominated solid-like elastic behavior. Droplet-size distribution was measured by light scattering and microscopic observations revealed a flocculated system. Gum, WPI, and oil contents decreased the emulsion creaming index with gum concentration having the greatest effect.     

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.     

Comparison of the Rheological Behavior of Solutions and Formulated Oil-in-Water Emulsions Containing Carboxymethylcellulose (CMC)

In this study, it was aimed to compare the rheological properties of carboxymethylcellulose (CMC) in aqueous solutions and their corresponding emulsions containing 0.05, 0.1, 0.25, and 0.5% CMC in the aqueous phase. Samples with 0.05 and 0.1% CMC showed Newtonian behavior, but shear-thinning behavior was observed in CMC solutions and emulsions with increasing CMC concentrations to 0.25% and 0.5%. Rheological behavior of all samples were modeled by Power law (R ² = 0.986–197) and Casson models (R ² = 0.968–1). According to the Ostwald–de Waele model, the consistency index of all samples was increased and the flow behavior index decreased with increasing CMC concentration. Comparison of our data with four predicting models (Einstein, Larson, Pal, and Dougherty-Krieger equations) showed that the viscosity of continuous phase controls the viscosity of emulsions with high CMC concentrations and these models are not applicable for such situations. Addition of CMC increased the emulsion stability of O/W emulsions. This stability was increased with increasing CMC concentrations.     

Rheological technique for determining the order–disorder transition of block copolymers

A rheological technique is proposed for determining the thermally induced order–disorder transition of block copolymers. In the present investigation, a cone-and-plate rheometer was used to measure dynamic storage and loss moduli, G′(ω) and G″(ω), as a function of angular frequency ω of a commercial grade polystyrene-block-polyisoprene-block-polystyrene (SIS) tri-block copolymer (KRATON D-1107, Shell Development Company) in the temperature range from 140 to 240°C. For comparison purposes, dynamic viscoelastic properties of a commercial grade low-density polyethylene (LDPE) were also determined in the temperature range from 160 to 238°C. We have found that log G′ versus log G″ plots for the LDPE show no temperature dependence, whereas log G′ versus log G″ plots for the SIS block copolymer do show systematic temperature dependence in the temperature range 140–230°C. This observation leads us to conclude that the order–disorder transition of the SIS block copolymer takes place gradually as the temperature is raised from 140 to 230°C. This conclusion is in good agreement with that drawn from the study of Roe (Ref. 33), who employed the same block copolymer using small-angle x-ray scattering. It is not possible to reach such a conclusion using log G′(ω) versus log ω, log G″(ω) versus log ω, or log η′(ω) versus log ω plots in which η′ is the dynamic viscosity. We have demonstrated further that the use of frequency-temperature superposition is inappropriate for investigating the rheological behavior of block copolymer in the temperature range over which a thermally induced transition from an ordered structure to a disordered homogeneous phase occurs. We therefore suggest that when using information on dynamic viscoelastic properties, log G′ versus log G″ plots be used for determining the thermally induced order–disorder transition of block copolymers.     

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     

Inhibition Effect of N-(Pyridin-2-yl-Carbamothioyl) Benzamide on the Corrosion of C-Steel in Sulfuric Acid Solutions

N-(Pyridin-2-yl-carbamothioyl)benzamide (PCMB) was newly synthesized and tested as a corrosion inhibitor for C-steel in 0.5 M H₂SO₄ using chemical and electrochemical techniques. Polarization measurements showed that the synthesized compound acted as a mixed inhibitor. The inhibition efficiencies obtained from the different methods were in good agreement. The inhibitive action of this compound is discussed in terms of blocking the electrode surface by adsorption of the inhibitor according to the Langmuir isotherm. The effect of temperature on the corrosion behavior in the absence and presence of 2.5 × 10^?5 M of PCMB was studied (283–308 K). The associated activation energies (E _a) and the thermodynamic parameters (ΔH*, ΔS*, K _ads, ΔG°_ads) for the adsorption process were determined. The ΔG°_ads value is ?36.55 kJ/mol, which indicated that the adsorption mechanism of PCMB on C-steel in 0.5 M H₂SO₄ solution was combined between physisorption and chemisorption processes.     

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     

Rheological Properties of SiC Suspensions with a Compound Surface Modification Using Ethyl Orthosilicate and Ethylene Glycol

Ultrafine silicon carbide (SiC) powders were surface-modified using ethyl orthosilicate (TEOS) combined with ethylene glycol. SiC suspensions with favorable rheological properties, low viscosity, and high solid loading were successfully obtained. The mechanisms of the compound surface modification for SiC powders as well as the influences of the compound surface modification not only on functional groups and charge state of the surface for SiC powders but also on the rheological properties of SiC suspensions were investigated in the present study. The results show that under alkaline conditions and acidic conditions, the surface charge states of SiC powders were [Si-OCH₂CH₂O]^? and [Si-OCH₂CH₂OH₂]⁺, respectively. The absolute value of zeta potential reached the maximum value of 22.69 mV at pH 11. Additionally, with added 1 wt% TEOS and 3 wt% ethylene glycol, the SiC suspensions exhibited good rheological properties, low viscosity and high stability due to the steric hindrance and electrostatic repulsion offered by the [Si-OCH₂CH₂O]^- with a high concentration.     

Rheology of Aqueous Solutions Containing SLES,CAPB, and Microemulsion: Influence of Cosurfactant and Salt

Aqueous solutions containing sodium lauryl ether sulphate (SLES) and cocamidopropyl Betaine (CAPB) with a constant total surfactant concentration (10 wt%) but different volume mixing ratios were prepared. A remarkable increase in the solutions’ viscosity at a volume mixing ratio of 34 v/v% SLES to 66 v/v% CAPB was observed. By increasing the volume ratio of SLES (r-value) in the binary mixture, the viscosity of 10 wt% SLES, which is close to that of water, increases to a maximum, but then drops down drastically at high r values (>45 v/v%). The maximum viscosity (V_max) is 2.8 Pas, whereas the minimum is 2 mPas. The rheological behavior at V_max has the remarkable feature of a simple Maxwell fluid over a large frequency range with one relaxation time. By adding a microemulsion (Plantasil Micro), the value of V_max decreases extremely, whereas adding cosurfactants like isodecyltrietheleneoxide (IT₃) or salts, like calcium chloride, leads to a pronounced increase in the value of V_max. At 0.76 wt% CaCl₂, V_max is 140 Pas and 150 Pas in the presence of 1 wt% IT₃. By increasing the SLES volume mixing ratio in the solution the maximum viscosity is shifted to higher CaCl₂ amounts. The increasing viscosity can be explained by a transformation of the micelle shape from spherical to rod-like. Whereas adding cosurfactants or salts leads to an increased entanglement between the rod-like micelles. Consequently, higher microemulsion amounts can be added before reaching the minimum viscosity.     

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     

On the Origin of Foam Stability: Understanding from Viscoelasticity of Foaming Solutions and Liquid Films

The foam stability (drainage half-life) of α-olefin sulfonate (AOS) with partially hydrolyzed polyacrylamide (HPAM) or xanthan gum (XG) solution was evaluated by the Warring Blender method. With the increase of polymer (HPAM or XG) concentration, foam stability of the surfactant–polymer complexes increased, and the drainage half-life of AOS-XG foam was higher than that of AOS-HPAM foam at the same polymer and surfactant concentration. With the addition of polymer (HPAM or XG), the viscoelasticity of bulk solution and the liquid film were enhanced. The viscoelasticity of AOS-XG bulk solution and liquid film were both higher than that of AOS-HPAM counterparts.      

Rheological behavior and reversible swelling of pH sensitive poly(acrylamide-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) hydrogels

The study involved preparation of poly(acrylamide-co-itaconic acid) hydrogels by radical cross-linking copolymerization. The copolymer hydrogels were characterized through infrared spectroscopy, thermal analysis, swelling measurements and in oscillatory and steady shear rheology. Results showed that more stable copolymers were formed due to the strong interaction in the hydrogels. These hydrogels have shown substantial percent swelling in water and shrinking in saline solution and acidic buffers. The rheological properties were described by the Herschel-Bulkley and power-law models to explore their non-Newtonian behavior. The results showed that higher itaconic acid content raised the polymer viscosity; the degree of shear-thinning and polymer elasticity (G′) were also increased. The transition from the viscous (G′ < G″) to the predominant viscoelastic behavior (G′ > G″) occurs at a crossover frequency ranged from 17.8 rad/s for polyacrylamide to 15.7, 12.8 and 12.5 rad/s for copolymers.     

Effect of Surfactant Chain Length on the Rheological Properties of Cationic Surfactants and a Hydrophobic Counterion

The rheological behavior of alkyimethylammonium 2-hydroxy-1-carboxy-naphthoate, C_xTA-2.1-HCN (x = 16, 14, 12, 10, and 8) is presented. With increasing 2.1 HNC/C_xTAOH (x = 16, 14, 12) ratio, the viscoelasticity of the solutions changes due to a transition in the micellar shape from small micelles to rodlike micelles and finally to multilamellar vesicles (MLV). On the other hand, a transition from small micelles to multilamellar vesicles (MLV) was observed for solution with C_xTA-2.1-HCN (x = 10 and 8). The MLV phases behave like a weak gel and have a yield stress value. Rheological measurements were performed for these viscoelastic systems in order to find out the dependency of the viscoelastic behavior on the surfactant chain length and hydrophobic counterion concentration. Some theoretical models as reptation mechanism was also applied in order to get some structural details and to illustrate the rheological behavior of these viscoelastic systems. Some models that correlate MLV-modulus on the surfactant morphology are also presented and discussed.