Aqueous Guar Gum Research Articles

Characteristics of Biopolymer Guar Gum Solution Injection for Eco-Friendly Ground Reinforcement

Recently, research on the use of biopolymers for environmentally friendly soil improvement has been actively conducted. Biopolymer soil treatment has various effects, such as the enhancement of soil strength, reduction of hydraulic conductivity, and enhancement of vegetation. In this study, the flow and injection characteristics of guar gum solutions were analyzed to develop biopolymer-based injection materials. Viscosity measurements and micromodel experiments were conducted to analyze the flow and injection properties. Viscosity measurements indicated that the guar gum solution showed a tendency of shear-thinning, in which the viscosity decreased as the shear rate increased. By applying the Power-law, the consistency index tended to increase as the concentration of aqueous guar gum solution increased. However, no clear trend was observed for the behavior index. As a result of the micromodel experiment, the pore saturation tended to increase as the volumetric flow rate and concentration of the guar gum solution increased. This is because of an increase in the injection pressure and apparent viscosity. When applied to an actual field, the required injection pressure varies depending on the ground conditions. Therefore, the results of this study will be used as fundamental data for determining the concentration of aqueous guar gum solution suitable for ground conditions.

Slowing the Starch Digestion by Structural Modification through Preparing Zein/Pectin Particle Stabilized Water-in-Water Emulsion.

Slowing the digestion of starch is one of the dominant concerns in the food industry. A colloidal structural modification strategy for solving this problem was proposed in this work. Due to thermodynamic incompatibility between two biopolymers, water/water emulsion of waxy corn starch (WCS) droplets dispersed in a continuous aqueous guar gum (GG) was prepared, and zein particles (ZPs), obtained by antisolvent precipitation and pectin modification, were used as stabilizer. As the ratio of zein to pectin in the particles was 1:1, their wetting properties in the two polysaccharides were similar, which made them accumulate at the interface and cover the WCS-rich droplets. The analysis of digestibility curves indicated that a rapid (rate constant k1: 0.145 min-1) and a slow phase ( k2: 0.022 min-1) existed during WCS digestion. However, only one slow phase ( k2: 0.019 min-1) was found in the WCS/GG emulsion, suggesting that this structure was effective in slowing starch digestion.

Viscoelastic properties of aqueous guar gum derivative solutions under large amplitude oscillatory shear (LAOS)

The industrial relevant nonlinear viscoelastic properties of aqueous carboxymethyl hydroxypropyl guar gum (CMHPG) and non-ionic hydroxypropyl guar gum (HPG) solutions between semi-dilute and concentrated solution state were investigated by large amplitude oscillatory shear flow (LAOS). Aqueous CMHPG and HPG solutions enter the nonlinear flow regime at deformations γ0>100%. The nonlinear stress waveforms were analyzed by FT-rheology and orthogonal stress decomposition along the MITlaos framework. A rheological fingerprint is generated (Pipkin space) showing that the guar gum derivative solutions undergo a shear-thinning at high strains, which is preceded by a thickening above a minimum strain rate at intermediate strains. The influence and breakup of superstructures/aggregates gives a “rheological fingerprint”, a function of the applied deformation and time scale (Pipkin space). A characteristic process time was found that scales exponentially with the overlap parameter with an exponent of 4/2, and is proposed to represent the relaxation process of the superstructure in solution.

Extensional flow behavior of aqueous guar gum derivative solutions by capillary breakup elongational rheometry (CaBER)

The extensional rheological properties of aqueous ionic carboxymethyl hydroxypropyl guar gum (CMHPG) and non-ionic hydroxypropyl guar gum (HPG) solutions between the semi-dilute solution state and the concentrated network solution state were investigated by capillary breakup elongational rheometry (CaBER). Carboxymethylated guar gum derivatives show an instable filament formation in deionized water. The ratio of elongational relaxation time λE over the shear relaxation time λS follows a power law of λE/λS∼(c·[η])−2. The difference of the relaxation times in shear and elongation can be related to the loss of entanglements and superstructures in elongational flows at higher strains.

Ultrasound assisted enzymatic depolymerization of aqueous guar gum solution

The present work investigates the effectiveness of application of low intensity ultrasonic irradiation for the intensification of enzymatic depolymerization of aqueous guar gum solution. The extent of depolymerization of guar gum has been analyzed in terms of intrinsic viscosity reduction. The effect of ultrasonic irradiation on the kinetic and thermodynamic parameters related to the enzyme activity as well as the intrinsic viscosity reduction of guar gum using enzymatic approach has been evaluated. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. It has been observed that application of ultrasound not only enhances the extent of depolymerization but also reduces the time of depolymerization as compared to conventional enzymatic degradation technique. In the presence of cellulase enzyme, the maximum extent of depolymerization of guar gum has been observed at 60W of ultrasonic rated power and ultrasonic treatment time of 30min. The effect of ultrasound on the kinetic and thermodynamic parameters as well as the molecular structure of cellulase enzyme was evaluated with the help of the chemical reaction kinetics model and fluorescence spectroscopy. Application of ultrasound resulted in a reduction in the thermodynamic parameters of activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) by 47%, 50%, 65% and 1.97%, respectively. The changes in the chemical structure of guar gum treated using ultrasound assisted enzymatic approach in comparison to the native guar gum were also characterized by FTIR. The results revealed that enzymatic depolymerization of guar gum resulted in a polysaccharide with low degree of polymerization, viscosity and consistency index without any change in the core chemical structure which could make it useful for incorporation in food products.

Intensification of depolymerization of aqueous guar gum using hydrodynamic cavitation

Depolymerization of aqueous guar gum using hydrodynamic cavitation has been investigated for the first time, with a detailed understanding into the effect of initial concentration of polymer, inlet pressure, geometry of cavitating device, operating temperature and addition of potassium persulfate (KPS). The extent of depolymerization has been analyzed in terms of reduction in intrinsic viscosity using Ubbelohde glass capillary viscometer. It has been observed that lower initial concentration, higher inlet pressure, slit venturi as cavitating device and addition of KPS result in higher extent of depolymerization. Use of hydrodynamic cavitation alone under optimized conditions resulted in about 70% reduction in intrinsic viscosity whereas addition of KPS under optimum loading enhanced the extent of reduction to 96%. Kinetic analysis established that the kinetic rate constant increased with an increase in the temperature and concentration of KPS. FTIR analysis demonstrated that there were no structural changes and the chemical identity was retained. Hydrodynamic cavitation has been demonstrated to be more energy efficient and applicable at larger scale of operation as compared to ultrasound based operation.

Effect of bubble volume fraction on the shear and extensional rheology of bubbly liquids based on guar gum (a Giesekus fluid) as continuous phase

The effect of air bubble volume fraction, ϕ, on the steady shear and extensional rheology of aqueous guar gum solutions was studied at 0⩽ϕ⩽0.25 and gum concentrations of (i) 5g/L and (ii) 10g/L, corresponding to solutions in the (i) semi-dilute and (ii) entanglement regime. The rheological response of the fluids was largely independent of bubble size but strongly dependent on ϕ. The viscous and elastic moduli increased with increasing bubble volume fraction, with elastic dominance prevalent at the higher gum concentration. Extensional rheometry, investigated using filament stretching, revealed that the thinning dynamics of the liquid thread were affected by bubble size, but the filament rupture time was primarily dependent on ϕ. The rheological behaviour in both shear and extension could be modelled as a single mode Giesekus fluid, with a single set of parameters able to describe both the shear and extensional behaviour in the semi-dilute regime. In the entanglement regime the single mode Giesekus fluid could fit the shear data or the extensional data individually, but not both. The fitted Giesekus fluid model parameters exhibited a strong dependency on ϕ, offering a way to predict the flow behaviour of these complex food fluids.

Polyelectrolytic aqueous guar gum for adsorptive separation of soluble Pb(II) from contaminated water

The article introduces the concept of homophase adsorption of soluble Pb(II) from contaminated water using aqueous guar gum (GG). The process appears to be extremely handy since it avoids hectic sample preparation and adsorbent recovery stages. The results show that, addition of only 1000ppm GG removes 56.72% of the contaminated Pb(II) within 150min at 303K. The best working pH has been found to be at 4.5. At this point GG molecules show greatest balance between negative zeta potential and high molecular size. Mechanistically, the adsorption follows Langmuir model since on formation of a monolayer, the positive Pb(II) prevent subsequent adsorption through strong electrostatic repulsion. The adsorption kinetics follows pseudo second order model. Both kinetics and thermodynamics of the process complies with the conventional hetero facial adsorption models despite huge procedural differences.

Effect of concentration on shear and extensional rheology of guar gum solutions

The steady shear and extensional rheology of aqueous guar gum solutions was studied for concentrations, C, ranging from 1 g/L to 20 g/L. Extensional rheometry measurements were made using the Cambridge Trimaster filament-stretching device. The steady shear tests indicated a transition between a semi-dilute regime, below 10 g/L, and an entangled regime at higher concentrations. The solutions were shear-thinning and obeyed the unmodified Cox–Merz rule in the dilute regime, but deviated from Cox–Merz and exhibited strongly viscoelastic behaviour at higher concentrations. The surface tension at higher concentration also deviated from the Szyszkowski model, exhibiting behaviour consistent with entanglement. The filament-thinning data did not fit the model for polymer solution behaviour presented by Entov and Hinch (1997), but gave a good fit to a modified form where time was normalised by the time for filament break-up. This scaling was independent of concentration effects, as reported by Chesterton, Meza, Moggridge, Sadd, and Wilson (2011) for cake batters. The modified model parameters approached asymptotic values for entangled solutions. The estimated apparent extensional viscosity exhibited a peak at unit strain followed by a constant value. The former increased as Cn, where n > 1, while the latter increased linearly with C.

Ethanol-resistant ethylcellulose/guar gum coatings – Importance of formulation parameters

Recently, ethylcellulose/guar gum blends have been reported to provide ethanol-resistant drug release kinetics from coated dosage forms. This is because the ethanol insoluble guar gum effectively avoids undesired ethylcellulose dissolution in ethanol-rich bulk fluids. However, so far the importance of crucial formulation parameters, including the minimum amount of guar gum to be incorporated and the minimum required guar gum viscosity, remains unclear. The aim of this study was to identify the most important film coating properties, determining whether or not the resulting drug release kinetics is ethanol-resistant. Theophylline matrix cores were coated in a fluid bed with blends of the aqueous ethylcellulose dispersion “Aquacoat®ECD30” and guar gum. The polymer blend ratio, guar gum viscosity, and degree of dilution of the final coating dispersion were varied. Importantly, it was found that more than 5% guar gum (referred to the total polymer content) must be incorporated in the film coating and that the apparent viscosity of a 1% aqueous guar gum solution must be greater than 150cP to provide ethanol-resistance. In contrast, the investigated degree of coating dispersion dilution was not found to be decisive for the ethanol sensitivity. Furthermore, all investigated formulations were long term stable, even upon open storage under stress conditions for 6months.

Guar gum and guar gum-oligomeric poly(vinyl alcohol) blends as novel flocculants for kaolinated waste water

This is probably the first report on kaolin flocculation done with aqueous guar gum (GG) at various pH. Dynamic light scattering and reduced viscosity proved the polyelectrolytic feature (zeta potential) of aqueous GG which changed on changing pH. Interestingly, the molecular size of GG did not always increased with rising zeta potential due to strong intermolecular repulsion leading to macromolecular recoiling. Best pH range for settling was 4.0–5.0 which included isoelectric point (IEP) of kaolin. Post-settling turbidity was also acceptable at that range. Optimized GG was further blended with oligomeric poly (vinyl alcohol) (PVA) (Mn 14,000) to prepare a new set of flocculant. Oligomeric PVA was previously optimized at similar pH as excellent kaolin flocculant in our earlier investigation. All GG–PVA blends including neat GG exhibited faster settling than neat PVA. However, settling times of all blend compositions were slightly greater than that of neat GG except for few cases where the post settling turbidity was found significantly lower than all our previous investigations.

Effect of water and guar gum content on thermal properties of chestnut flour and its starch

Thermal properties of chestnut flour and chestnut starch at several water content (40, 50, 60 and 95%, flour basis, f.b.) as well as the influence of guar gum (0.5, 1.0, 1.5 and 2.0%, f.b.) on both raw materials at fixed water content (50%, f.b.) were determined by differential scanning calorimetry (DSC). Thermal properties of guar gum–water systems at several guar content (0.5, 1.0, 1.5 and 2.0%, w/w) were also obtained by DSC. Results indicated that the water content and the presence of guar gum had a significant impact on the thermal properties of chestnut flour and its starch. For each endothermic curve, the values of onset (To), peaks (Tp1, Tp2) and final (T1) temperatures decreased linearly with increasing water content. Experimental data were successfully (R2 > 0.997) described following the Flory equation. A reverse trend was observed in the enthalpy values. Thermal properties of chestnut flour and chestnut starch were suppressed by the presence of guar gum even at the lowest concentrations employed (0.5%, f.b.). The guar gum addition to the assayed systems promoted a starch gelatinization delay and the enthalpy values showed a threshold content above 1.0% of guar gum. Analyses of aqueous guar gum mixtures showed that the existence of a second transition in chestnut starch systems can be successfully explained by means of hydrocolloid–starch interactions, whereas in the flour other interactions should be taken into account.

Dissolution kinetics of water-soluble polymers: The guar gum paradigm

The ability of many water/electrolyte soluble polymers (WSPs), such as guar galactomannan, to form molecular solutions when dispersed in water is important industrially, for example in food applications, and in controlling the release of drugs in the gastrointestinal tract. Certain WSPs, including guar, are also referred to generically as ‘soluble fibre’ and some of these fibre preparations are currently available on prescription in the UK and elsewhere. The functional and exploitational properties of such polymers are reliant on the solution viscosity, which is, in turn, dependent on the rate and extent of dissolution in the aqueous solvent. This work extends previous experimental work on the effect of particle size on the dissolution (hydration) rate of guar gum powders over a wide range of particle sizes. In this earlier work, the main experimental variable was the solution viscosity, but we extend this by calculating a new effective concentration from the viscosity and exploring the dissolution rates in terms of this variable. The advantages and limitations of this approach are discussed, and a number of dissolution models, some well known and others novel, are explored. These include t 50, diffusion limited and chemical kinetics models. In view of the results, we suggest because of the particulate size, the model based on chemical kinetics appears the most successful. Aqueous guar gum is a model “entanglement solution” system, so the work should have applicability to many other WSP systems.

Linear Viscoelastic Behavior of Enzymatically Modified Guar Gum Solutions: Structure, Relaxations, and Gel Formation

To gain more insight into the mechanisms of stress relaxation in aqueous guar gum solutions, we investigated the effect of chemical modifications of the polymer and of the solvent on the linear viscoelastic behavior in different regions of the frequency domain. Interchain bonding could be ruled out as the origin for the high-frequency relaxation behavior, while it was corroborated that such a bonding must be (directly or indirectly) involved in the relaxations at low frequencies. In the enzymatic modifications, galactose side groups were removed in different fractions f (0.30−0.57) of the available amount. Moduli were measured as a function of frequency (0.003−20 Hz) and temperature (283−323 K). On increasing f, a transition from a liquid to a gel was found at f = fc. Below fc the changes in the relaxation behavior were very modest, and changing the solvent had little effect. Above fc gels were formed. The low-frequency storage moduli strongly increased whereas the high-frequency moduli remained essentially unchanged. For both modified and unmodified guar solutions, we attribute the viscoelastic response at high frequencies to conformational relaxations of multichain structures and at low frequencies to interchain bonding effects. More detailed mechanistic information is hard to obtain. Yet we propose a microscopic picture that can explain most of our observations. It would merit a further study with other techniques. The possibility to make weak gels of α-d-galactosidase-treated guar was demonstrated, and also this deserves further study.

Heat transfer to model non-Newtonian liquid foods in cans during end-over-end rotation

Heat transfer coefficients were determined for aqueous guar gum solutions (0·3%, 0·4%, 0·5%, and 0·75%) during end-over-end rotation in copper cans. The variables investigated were size of can, speed of rotation and radius of rotation. The centre temperature within the can was found to oscillate. Over the range of variables studied, the heat transfer coefficient was found to be independent of the radius of rotation and the size of the can. The heat transfer data for non-Newtonian fluids were correlated in terms of Nusselt (Nu), generalised Reynolds (GRe), and generalised Prandtl (GPr) numbers: Nu = 1.41GRe 0.482GPr 0.355 The correlation was found to be similar to that developed earlier for Newtonian liquids.

LITERATURE ABSTRACTS

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Effect of Heat Treatment on the Flow Properties of Aqueous Guar Gum and Sodium Carboxymethylcellulose (CMC) Solutions

ABSTRACTProlonged heat treatment of 1% (w/v) guar gum and sodium carboxymethylcellulose (CMC) solutions resulted in a permanent loss of their apparent viscosity. The consistency index (K) of the power law model: τ= K γn, indicated well the loss of viscosity. The reduction in K due to heat treatment could be characterized by D and z parameters. The D250 and z values for guar gum were 32 min and 62°F, respectively; the magnitudes for CMC were 7.9 min and 48°F, respectively. These values were obtained from experiments in which the solutions were placed in sealed cans (201 × 304) and subjected to temperatures between 210–260°F. Because the solutions were viscous, corrections were made for heating and cooling lags during heat treatment. Dilutee solution viscosity data showed that heat treatment resulted in lower magnitudes of intrinsic viscosities and interaction coefficients. The activation energy of flow of the heat‐treated solutions was not affected significantly due to heat treatment.