Viscoelastic properties of lupin proteins produced by ultrafiltration-diafiltration

The linear and nonlinear rheological properties of defatted lupin proteins produced by ultrafiltration-diafiltration were investigated. Five concentrations ranging from 10 to 30% of the defatted ultrafiltered-diafiltered (DUD) lupin proteins were prepared. The viscoelastic properties strongly depended on concentrations. Below 12%, the DUD lupin proteins exhibited more fluid-like behavior. At 15%, lupin proteins became more viscoelastic, and above 20%, the viscoelastic solid-like properties became stronger. Below 12%, the high-frequency behaviors of moduli were proportional to ω^1/2, as expected for a semiflexible coil. Above 20%, the high-frequency behaviors of moduli were proportional to ω^1/2, indicating a flexible coil. The nonlinear steady shear rheological properties were also concentration-dependent and showed shear-thinning behavior, which could be described by a power law constitutive model. The trend of the power law exponent shift is very consistent with the linear viscoelastic behavior change with the lupin protein concentration. These results suggest DUD lupin proteins undergo a structural change between 12 and 20%.     

Effect of heat treatment and pH on the thermal,surface, and rheological properties of <Emphasis Type="Italic">Lupinus albus</Emphasis> protein

Endosperm from hand-dissected and- dehulled Lupinus albus seeds was milled into meal, sieved through a 40-mesh screen, and suspended in phosphate buffers (pH 4, 6.8, and 8) at 20% (wt/vol). The suspensions were treated at 75, 90, or 100°C for 1 h. The heat-treated protein was characterized by SDS-PAGE, free zone capillary electrophoresis (FZCE), and DSC; and its surface hydrophobicity, surface tension, and rheological properties were examined. The presence of high M.W. aggregates was apparent from SDS-PAGE and FZCE results. Solubility was lowest at pH 4 and 100°C. DSC analysis was performed on low moisture content samples (3.1%) and 20% (wt/vol) suspensions. DSC analysis at 3.1% moisture content showed a glass transition around 85°C and an exothermic transition at 160°C, whereas the protein suspension showed a more thermally stable protein as indicated by the higher ΔH values. Lupin protein was surface active as demonstrated by its effectiveness in reducing the surface tension of the aqueous phosphate buffer. Surface hydrophobicity of the heat-treated protein decreased as the treatment temperature increased, which supports the SDS-PAGE results. The highest level of aggregation was noted at 90°C and pH 6.8 as indicated by low surface hydrophobicity values. Rheological studies showed direct relationships between the shear storage modulus (G′) of the lupin meal suspension and both pH and temperature treatment, although this effect is minimal at the highest temperature (100°C) and pH 6.8.     

Linear and nonlinear rheological responses in aqueous systems of hydrophobically modified chitosan and its unmodified analogue

Oscillatory shear and viscosity measurements have been carried out on semidilute acid aqueous systems of unmodified chitosan (UM-chitosan) and of hydrophobically modified chitosan (HM-chitosan) with three different degrees of C12-aldehyde substitution. These systems form physical gels at higher concentrations. The gel point, determined by the observation of a frequency independent loss tangent, was found to be shifted toward lower concentrations with increasing hydrophobicity. At the gel point, a power law frequency dependence of the dynamic moduli (G′∼G″∼ω ⁿ) was observed, with n values of 0.36 and 0.46 for the UM-chitosan and the hydrophobically modified chitosans, respectively. These values are interpreted in the framework of a fractal model. The gel strength parameter S increased with decreasing hydrophobicity. The UM-chitosan and HM-chitosan systems exhibited a non-Newtonian shear thinning behavior. This effect is promoted by increasing polymer concentration and hydrophobicity. Both the linear and nonlinear rheological properties elucidate the intricate interplay between hydrophobic associations and entanglement effects. Received: 13 October 1997/Accepted: 24 October 1997     

Rheological prediction of the physical stability of concentrated dispersions containing particulates

A dynamic rheological technique is presented that can be used for the prediction of physical stability of concentrated dispersions containing particulates, as well as product development and quality control. Typical physical evaluation frequently requires weeks or months before an assessment can be made. By using dynamic rheology, the prediction of physical stability can often be accomplished in less than three (3) hours. The dynamic or oscillatory rheology technique is performed in two parts. First, a strain sweep test (frequency constant, strain variable) defines the linear viscoelastic range (LVR). Second, frequency scans (from 0.01 to 5.0 Hz) are performed at various temperatures, from 5 to 49°C (40–120°F). It is critical that the frequency scans are performed in the LVR. Dynamic rheology measurements yield data on the elastic (G′) and viscous (G″) moduli. Plotting the elastic to viscous moduli ratio as a function of frequency and temperature generates a 3-D surface which is a “fingerprint” of the dispersion’s colloidal stability. The G′/G″ ratios correlate well with observed physical stability properties. A volume index or a simple mean/variance calculation can be used to assign a value to the graphical 3-D representations. Presented April, 1990, at the AOCS National Meeting, Baltimore, MD.     

Characterization of Gelation of Aqueous Pectin via the Ugi Multicomponent Condensation Reaction

Summary Turbidity and rheological features during gelation of semidilute solutions of pectin via the Ugi multicomponent condensation reaction have been investigated at different polymer and cross-linker concentrations at ambient temperature. The gelation time of the system decreased with increasing polymer and cross-linker concentrations. At the gel point, a power law frequency dependence of the dynamic storage modulus (G’∼ω^n’) and loss modulus (G”∼ω^n”) was observed with n’=n”=n. The value of the power law exponent is about 0.6∼0.7 for all the gelling systems, which is close to that predicted (0.7) from the percolation model. The elastic properties of the gels continue to grow over a long time in the post-gel region, and a solidlike response is observed at later stages during the gelation process. The turbidity of the gelling system is higher as the polymer and cross-linker concentrations rise, but the turbidity is virtually unaffected during an extended time after the formation of the incipient gel. It was demonstrated that polymer and cross-linker concentrations could be utilized to tune the physical properties, such as transparency and viscoelasticity, of the Ugi hydrogels.     

Lupin protein concentrates by extraction with aqueous alcohols

In order to remove the toxic quinolizidine alkaloids and other nonprotein constituents, hexane-defatted flakes of lupin (Lupinus mutabilis) were extracted under various conditions with ethanol, methanol or their aqueous solutions. Lupin protein concentrates containing more than 70% protein and 0.1–0.2% alkaloids were obtained in high yields by consecutive extractions, countercurrent extraction or semicountercurrent extraction of the defatted lupin flakes with either 80% ethanol or 80% methanol.     

Optimization of the composition of low-fat oil-in-water emulsions stabilized by white lupin protein

The effect of composition (protein, xanthan gum, and oil content) of lupin protein-stabilized emulsions on their physical properties—droplet size distribution, rheological behavior, and texture—was studied. Droplet size distribution was measured by laser light-scattering experiments, rheological parameters were determined from oscillatory and steady-state flow measurements, and texture responses were obtained from texture profile analysis. Response surface methodology was used to optimize the emulsion composition using commercial mayonnaise parameters as a standard. An increase in protein, xanthan gum, or oil content produced, in the experimental range considered, an increase in the rheological and textural parameters studied, as well as a decrease in the average oil droplet diameter. It was possible to produce stable lupin protein-stabilized emulsions with physical properties similar to those of commercial mayonnaise for a wide variety of protein, xanthan gum, and oil concentration values, which may be designed to suit market specifications.     

Physicochemical and Rheological Properties of Crystallized Blends Containing <Emphasis Type="Italic">trans</Emphasis>-free and Partially Hydrogenated Soybean Oil

Three vegetable oil blends, intended for formulation of high melting temperature confectionary coatings, were prepared by mixing different proportions of coconut oil, palm stearin, and either partially hydrogenated soybean oil (PH-SBO) or native soybean oil (i.e., trans-free SBO). The blends were crystallized under the same isothermal conditions and the crystallized systems evaluated by DSC, SFC, polarized light microscopy, and rheology under low [i.e., G′ and yield stress (σ*)] and high (i.e., creep and recovery profiles) stress forces. Overall, all trans-free blends showed lower SFC and heat of crystallization than the ones obtained with PH-SBO blends. These results showed that trans-fatty acids decrease the level of structural order of the crystals, and probably also the organization of the crystal network. As a result, most of the crystallized blends with PH-SBO showed lower σ* values and higher creep profiles (i.e., softer texture) than trans-free blends, particularly in systems crystallized at high supercooling and blends with saturated medium chain TAG. Nevertheless, at particular crystallization temperatures some trans-free formulations provided crystallized systems with rheological properties that would result in softer textures than the ones obtained with PH-SBO blends. Knowledge of the rheological properties under low and high stress forces is vital when comparing the functionality of crystallized TAG systems with and without TAG with trans-fatty acids.     

A potential biodegradable rubber—Viscoelastic properties of a soybean oil-based composite

Scientists are more and more interested in biodegradable materials owing to their environmental advantage. We investigated viscoelastic properties of a newly developed biomaterial made from epoxidized soybean oil (ESO). ESO cross-linked by triethylene glycol diamine exhibited viscoelastic solid properties. The storage modulus (G′) was 2×10⁴ Pa over four frequency decades. The phase angles were 14–18°. Stress relaxation measurements showed that there was no relaxation up to 500 s. From the plateau modulus we estimated that the M.W. of this cross-linked soybean oil was on the order of 10⁵. The composites of cross-linked ESO with three different fibers had 50 times higher elasticity (G′) than those without fiber. Phase shifts were the same as those of cross-linked oil without fibers, but the linear range of rheological properties was much narrower than that of the material without fibers. All these results indicated that this new biopolymer made from soybean oil exhibited strong viscoelastic solid properties similar to synthetic rubbers. These rheological properties implied that this biomaterial has high potential to replace some of the synthetic rubber and/or plastics.     

Rheological behavior of starch–poly(vinyl alcohol)–TiO2 nanofluids and their main and interactive effects

In this study, an investigation of the rheological behavior of starch/poly(vinyl alcohol) (PVA)/titanium oxide (TiO₂) nanofluids was performed. It revealed that the rheological behavior of starch suspensions displays a particular change due to the presence of PVA and TiO₂. All examined fluids demonstrated non‐Newtonian behavior and followed the Power law model. The main and interacting effects of starch, PVA, and TiO₂ nanoparticles concentrations were studied using the analysis of variance. The results indicated that the flow behavior index (n), as well as the consistency index (K) of suspensions, is influenced by the PVA and TiO₂ contents. The flow behavior index (n) decreased and consistency index (K) increased by an increase in PVA concentration. A reverse trend is observed by the addition of TiO₂ nanoparticles to starch and PVA blend suspensions. The difference in rheological behaviors was ascribed to the presence of binary and triplet interactions between starch, PVA, and TiO₂ nanoparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44062.     

Thermo‐rheological properties and miscibility of linear low‐density polyethylene‐silsesquioxane nanocomposites

The influence of octakis(n‐hexadecyldimethylsiloxy)octasilsesquioxane (hdPOSS) on rheological and thermal properties of linear low‐density polyethylene was investigated. Rheological evaluations realized by two different measuring techniques (rotational and extensional rheometry) allowed to obtain a wide range of information concerning an influence of silsesquioxanes on rheological properties of polymeric matrix. The studies were complemented with Differential Scanning Calorimetry measurements. In order to evaluate the miscibility of thermoplastic matrix and hybrid organic‐inorganic nanosized filler, rheological investigations, Dynamic Mechanical Thermal Analysis and Scanning Electron Microscopy were applied. Simultaneously, based on the rheological and thermal investigations, the mechanism of interactions between polymeric matrix and silsesquioxanes was considered. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42825.     

Thermal properties and adhesion strength of modified soybean storage proteins

Soy proteins have shown great potential for adhesive and resin applications. This investigation characterized the thermal and adhesive properties of the major soy protein components conglycinin (7S) and glycinin (11S) after chemical modification. These globulins were extracted from defatted soy flour, then modified with either sodium hydroxide, sodium dodecyl sulfate (SDS), or urea. Modified 7S, 11S, and mixtures of 7S and 11S at varying ratios were evaluated for gluing strength with cherry veneer plywood and for thermal denaturation using DSC. Adhesive strength and water resistance were significantly improved for all proteins modified with sodium hydroxide. Gluing strength and water resistance were improved for SDS- and ureamodified proteins containing greater portions of 7S globulins. The opposite behavior was observed for proteins containing large amounts of 11S globulins. DSC results showed that the temperatures of denaturation (T _d ) decreased for the proteins modified with sodium hydroxide or urea, whereas the T _d values of proteins modified with SDS were similar to the unmodified proteins. These results suggested that, at the concentrations studied, sodium hydroxide or urea could denature soybean protein more effectively than SDS, resulting in lower protein thermal stability. Soybean proteins with high ratios of 11S had more ordered structures, as evidenced by the high enthalpy values of protein denaturation observed in DSC measurements.     

Rheological Characterization of Metalized and Non‐Metalized Ethanol Gel Propellants

The gellation of metalized and non‐metalized ethanol with a methylcellulose gelling agent and its effect on the rheological properties (flow and dynamic study) of these gels is reported herein. The rheological study shows that increasing the shear rate reduces the apparent viscosity for a given yield stress (for a shear rate range of 1 to 12 s⁻¹) for both shear rate ranges (1 to 12 and 1 to 1000 s⁻¹) covered in present experiment. The gellant and metal particle concentrations significantly influence the gel apparent viscosity. Distinct changes in thixotropic behavior were observed, while decreasing the concentration of MC gellant and Al metal particles in the ethanol gels. The dynamic study showed that all of the linear viscoelastic regions (LVE) of the gel samples were independent of strain percentage (1 to 10). The G′ values depended on the frequency and exceeded the G′′ values, which indicated a gel‐like highly structured material. The tanδ values showed that all of the ethanol gels were elastic and weak physical gels with a high degree of cross‐linking.     

POEGMA‐b‐PAA comb‐like polymer dispersant for Al2 suspensions

POEGMA‐b‐PAA comb‐like polymer is synthesized through RAFT polymerization, and it is employed as an efficient dispersant for Al₂O₃ suspensions. The POEGMA‐b‐PAA polymer consists of PAA chains and POEGMA comb‐like chains. The former provide electrostatic attraction between Al₂O₃ particles and polymer, while the latter extend to solution and maintain the stability of suspension due to strong steric hindrance. The adsorption is proven and the rheology behaviors of Al₂O₃ suspensions are strongly improved. Different POEGMA‐b‐PAA polymers with different length of side chains have similar but not identical rheological properties. The polymer with the appropriate length of side chain provides the biggest improvement to rheological properties of Al₂O₃ suspensions, such as apparent viscosity and granularity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43352.     

Synthesis and characterizations of branched poly(butylene succinate) copolymers with 1,2‐octanediol segments

Branched poly(butylene succinate) (PBS) copolymers were synthesized, from succinic acid (SA), 1,4‐butanediol (1,4‐BD), and 1,2‐octanediol (1,2‐OD) through a two‐step process containing esterification and polycondensation, with different mole fractions of 1,2‐OD segments. The branched PBS copolymers were characterized with ¹H‐NMR, differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), thermogravimetric analysis (TGA), dynamic rheological testing, and tensile properties analysis. The results of DSC and WAXD show that, with the increasing of the 1,2‐OD segments content, the glass transition temperature (T_g), melting temperature (T_m), crystallization temperature (T_c), and the degree of crystallinity (X_c) decrease. While the crystal structure of PBS does not change by introducing 1,2‐OD segments. The results of TGA and dynamic rheological testing indicate that the thermal stability of neat PBS is improved with the addition of 1,2‐OD segments. The incorporation of 1,2‐OD segments has some effects on the rheological properties of PBS, such as complex viscosities (|η*|), storage modulus (G′), and loss modulus (G″). Tensile testing demonstrates that the elongation at break is improved significantly with increasing 1,2‐OD segments content, but without a notable decrease of tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheological study on the thermoinduced gelation behavior of poly(N‐isopropylacrylamide‐co‐acrylic acid) microgel suspensions

Submicron‐sized thermoresponsive poly(N ‐isopropylacrylamide‐co ‐acrylic acid) microgels were synthesized by soap‐free emulsion polymerization. The physical state of the microgel suspensions, in a wide range of polymer concentrations (1.1–7.1 wt %), transformed from fluid to gel when the temperature was elevated across their volume phase transition temperature at pH = 3.0. Such thermoinduced gelation behavior was studied in detail by small‐deformation oscillatory rheological measurements within the linear viscoelastic region. It was found that the gelation temperature was strongly affected by the polymer concentration, decreasing as the polymer concentration increased. The gelation kinetics showed that the suspension gelled more quickly at either larger polymer concentration or higher isothermal heating temperature. In an isothermal frequency sweep for the as‐formed gels, both storage and loss moduli, G′ and G″ , exhibited a power‐law behavior, that is, G′ (ω) ～ ω^0.2–0.4 and G″ (ω) ～ ω^0.46?0.50 within the frequency range where G′ dominates G″ . In addition, the elasticity of the gels, which results from the attractive particle bonds, increased markedly with increasing polymer concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45259.     

Phloem Alkaloid Tolerance Allows Feeding on Resistant Lupinus angustifolius by the Aphid Myzus persicae

We examined the hypothesis that the polyphagous green peach aphid (Myzus persicae) shows clone-specific adaptation to the narrow-leafed lupin (Lupinus angustifolius) containing toxic quinolizidine alkaloids. We compared the performance of a lupin-feeding clone of M. persicae from Western Australia to that of nine clones of the same species collected from eastern Australian locations, where narrow-leafed lupins rarely occur. Mean relative growth rate (MRGR) and colonization ability varied among the M. persicae clones on one aphid-susceptible and two aphid-resistant lupin varieties. The performance of the lupin-feeding clone was better than that of all other clones on the resistant narrow-leafed lupin varieties “Tanjil” and “Kalya”, indicating that successful lupin feeding is not a characteristic of the species. Gas chromatography-mass spectrometry analyses (GC-MS) of phloem from the different lupin varieties detected differences in the quantities of two alkaloid compounds identified as 13-OH-lupanine and lupanine. The lupin-feeding M. persicae clone also showed better performance on artificial diet amended with lupanine. The results suggest that the M. persicae clone collected from Western Australia is adapted to feed successfully on narrow-leafed lupin, and that this adaptation may involve improved tolerance of lupanine in its diet.     

The thermal,mechanical and viscoelastic properties of poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) (PBST) copolyesters with high content of BT units

Poly(butylene succinate-co-terephthalate) (PBST) copolyesters, with rigid butylene terephthalate (BT) units varying from 50 to 70 mol%, were synthesized via direct esterification route. The chemical structure and comonomer composition were characterized by ¹H NMR. The weight-average molecular weights (M _w ) of the prepared products measured by GPC spanned a range of 1.39 × 10⁵–1.93 × 10⁵ with corresponding M _w /M _n value of 2.23–2.42. Based on the WAXD analysis, PBST copolyesters were identified to have the same crystal structure as that of poly(butylene terephthalate) (PBT). The researches on the thermal properties showed that the melting temperature and decomposed temperature of PBST copolyesters increased with the increasing content of rigid BT units through DSC and TGA measurement. Furthermore, the tensile test results presented that the copolyester with higher content of BT units had higher initial modulus, higher breaking strength but lower elongation at break. Additionally, the viscoelastic properties of the prepared PBST films were analyzed by DMA measurement. It was found that both storage modulus (E′) and loss modulus (E″) corresponding to the peak tended to heighten with the increase of BT units, indicating the copolyester with higher BT units content had the more prominent viscoelasticity. The peak of loss factor (tan δ) curve shifted to higher temperature as the content of rigid BT units increased due to the increasing of the glass transition temperature (T _g).     

Thermal and mechanical properties of compression‐molded pMDI‐reinforced PCL/gluten composites

Many biopolymers and synthetic polymers composites were developed by different researchers for environmental protection and for cost reduction. One of these composites is polycaprolactone (PCL) and vital wheat gluten or wheat flour composites were prepared and compatibilized with polymeric diphenylmethane diisocyanate (pMDI) by blending and compression‐molding. PCL/pMDI blend exhibited glass transition (T_g) at ?67°C (0.20 J/g/°C) and vital gluten at 63°C (0.45 J/g/°C), whereas no T_g was recorded for wheat flour. Although T_g was unmistakable for either PCL or gluten, all composite exhibited one T_g, which is strong indication of interaction between PCL and the fillers. Several samples amongst the blended or compression‐molded composites exhibited no T_g signifying another confirmation of interaction. The ΔH of the endothermic (melting) and the exothermic (crystallization) for PCL was decreased as the percentage of gluten or flour increased, whereas the overall ΔH was higher for all composites compared to the theoretical value. The presence of pMDI appeared to strengthen the mechanical properties of the composites by mostly interacting with the filler (gluten or flour) and not as much with PCL. The FTIR analysis ruled out covalent interaction between PCL, pMDI, or the fillers but suggested the occurrence of physical interactions. Based on the data presented here and the data published earlier, the presence of pMDI did not change the nature of interaction between PCL and gluten, but it improved the mechanical properties of the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The prediction of lathering and solubility properties of bar soaps by differential scanning calorimetry

The present differential scanning calorimetry (DSC) study of eight commercial bar soap products has resulted in the assignment of DSC thermal absorptions to three key polymorphic states of soap (also known as“soap phases”): Δ,β,Ω. The DSC data have also been correlated with polymorphic states of soap identified previously by x-ray diffraction (XRD) method. The correlations of quantitative DSC data with consumer-perceived lathering attributes and experimentally determined solubility properties of these bars also are discussed. ¹ Presented at the American Oil Chemists’ Society Meeting, Baltimore, April 1990. *To whom correspondence should be addressed at American Soap Company, Inc., 11170 Green Valley Drive, Olive Branch, MS 38654.