Rheological and light scattering properties of flaxseed polysaccharide aqueous solutions

Polysaccharides isolated from flaxseed meals using ethanol consisted of a soluble ( approximately 7.5% w/w) and an insoluble fraction (2% w/w). The soluble fraction was dialyzed in various salt concentrations and characterized using viscometry and light scattering techniques. Observations using a size-exclusion column coupled to a multiangle laser light scattering (SEC-MALLS) revealed three molecular weight fractions consisting of a small amount ( approximately 17%) of large molecular weight species (1.0 x 10(6)) and a large amount ( approximately 69%) of small molecular weight species (3.1 x 10(5) Da). Dynamic light scattering measurements indicated the presence of very small molecules (hydrodynamic radius approximately 10 nm) and a very large molecular species (hydrodynamic radius in excess of 100 nm); the latter were probably aggregates. The intrinsic viscosity, [eta], of the polysaccharide in Milli-Q water was 1030 +/- 20 mL/g. The viscosity was due largely to the large molecular weight species since viscosity is influenced by the hydrodynamic volume of molecules in solution. The Smidsrod parameter B obtained was approximately 0.018, indicating that the molecules adopted a semi-flexible conformation. This was also indicated by the slope ( approximately 0.56) from the plot of root-mean-square (RMS) radius versus molar mass (M(w)).     

Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scattering

Dynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25 degrees C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 x 10(5) to 2.1 x 10(6) and ratios of the z-average radius of gyration (z) (1/2) to the hydrodynamic radius R(H) (calculated with previous (z) data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa-Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse-graining the heteropolysaccharide molecule. Excluded-volume effects are taken into account in the quasi-two-parameter scheme, as was done previously for (z) and [eta] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of R(H) is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm(-1), an excluded-volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from (z) and [eta] data, demonstrating that the solution properties (D, (z), and [eta]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied.     

Characterization of orange peel pectin and effect of sugars, -ascorbic acid, ammonium persulfate, salts on viscosity of orange peel pectin solutions

The effects of temperature and concentration on the viscosity of orange peel pectin solutions were examined at five different temperatures between 20 and 60°C and five concentration levels between 2.5–20 kg/m³. The effects of temperature was described by an Arrhenius-type equation. The activation energy for viscous flow was in the range 19.53–27.16 kJ/mol, depending on the concentration. The effect of concentration was described by two types of equation, power-law and exponential. Equations were derived which describes the combined effects of temperature and concentration on the viscosity for two different models in the range of temperatures and concentrations studied. Orange peel pectin was extracted by using HCl (pH 2.5, 90°C, 90 min) ammonium oxalate (0.25%, pH 3.5, 75°C, 90 min) and EDTA (0.5%, 90°C, 90 min) extraction procedures. The best result was obtained with ammonium oxalate extraction in which the pectin content of the final product was 30.12%, although the efficiency among the procedures varied.The average molecular weight was measured by light scattering technique. Magnitudes of intrinsic viscosity and molecular weight of pectins obtained by extraction with HCl, ammonium oxalate and EDTA were 0.262, 0.281, 0.309 m³/kg and 84 500, 91 400, 102 800 kg/kgmol, respectively. The molecular weight dependence of the intrinsic viscosity of the orange peel pectin solutions was expressed by Mark–Houwink–Sakurada equation. The data were fitted to equation as η_i=2.34×10⁻⁵(M_w,ave)^0.8224 which helps to evaluate the average molecular weight of pectin solutions from orange peel with a knowledge of their intrinsic viscosity.     

A hydrodynamic study of the depolymerisation of a high methoxy pectin at elevated temperatures

The hydrodynamic properties (intrinsic viscosity, [η]; infinite dilution sedimentation coefficient, s_20,w⁰; weight average molecular weight, M_w and translational frictional ratio, f/f₀) of a high methoxy pectin have been evaluated at various temperatures (20–60°C). A reduction in the value of all four hydrodynamic parameters is indicative of depolymerisation and is in agreement with an earlier study using viscometry [Axelos, M.A.V., & Branger, M., (1993). Food Hydrocolloids, 7, 91–102]. The apparent linearity of the Mark – Houwink plot of log[η] vs log M_w suggests that the conformation of the pectin molecule does not change significantly over the temperature range studied. The evaluation of the Mark–Houwink viscosity exponent (a=0.84) indicates a moderately extended structure. This then allows the calculation of the number of Kuhn statistical lengths per chain from the adapted ‘blob’ theory of Dondos [Dondos A. (2001). Polymer, 42, 897–901]. The weight average number of Kuhn statistical lengths per chain is reduced from (170±10) to (125±10) when the temperature is increased from 20–60°C. This may be of significance as many high methoxy pectins are exposed to high temperatures during processing in both the food and pharmaceutical industries.     

Purification and properties of an acidic protein from chromaffin granules of bovine adrenal medulla

1. A soluble protein has been purified from an aqueous extract of bovine adrenal chromaffin granules by chromatography on Sephadex G-200. This protein comprises 25% of the total protein of the granules and gave a single band on gel electrophoresis. 2. The protein is unusually rich in acidic amino acids, notably glutamic acid (26.0%, w/w); it is also relatively rich in proline (8.6%, w/w) but poor in cystine (0.35%, w/w). 3. A molecular weight of 77000 was obtained from sedimentation and diffusion measurements on the protein, and approach-to-equilibrium measurements gave apparent molecular weights of the same order. 4. A molecular weight 7 times that given above was estimated from the results of chromatography on a column of Sephadex G-200 that had been calibrated with globular proteins. However, good agreement between the ultracentrifuge and Sephadex experiments was obtained on the assumption that Sephadex chromatography depends on the effective hydrodynamic radii of proteins and not on their molecular weights. 5. The hydrodynamic properties of the protein differed from those of a typical globular protein. Thus the protein had a high intrinsic viscosity, a high frictional ratio and a large effective hydrodynamic volume. 6. The hydrodynamic properties of the protein, but not its molecular weight, were dependent on the ionic strength of the solvent. Increasing the ionic strength caused an increase in the sedimentation and diffusion coefficients, but a decrease in the intrinsic viscosity and in the frictional ratio of the protein. 7. Optical-rotatory-dispersion measurements indicated that only a small part of the polypeptide chain was in an alpha-helical conformation. 8. These results are compatible with the protein's having a conformation approaching that of a random-coil polypeptide, the volume occupied by the molecule being determined by electrostatic repulsion between the excess of negative charges.     

Bone-tissue-engineering material poly(propylene fumarate): correlation between molecular weight, chain dimensions, and physical properties

Poly(propylene fumarate) (PPF) is an important biodegradable and cross-linkable polymer designed for bone-tissue-engineering applications. For the first time we report the extensive characterization of this biomaterial including molecular weight dependences of physical properties such as glass transition temperature Tg, thermal degradation temperature Td, density rho, melt viscosity eta0, hydrodynamic radius RH, and intrinsic viscosity [eta]. The temperature dependence of eta0 changes progressively with molecular weight, whereas it can be unified when the temperature is normalized to Tg. The plateau modulus and entanglement molecular weight Me have been obtained from the rheological master curves. A variety of chain microstructure parameters such as the Mark-Houwink-Sakurada constants K and alpha, characteristic ratio Cinfinity, unperturbed chain dimension r0(2)/M, packing lengthp, Kuhn length b, and tube diameter a have been deduced. Further correlation between the microstructure and macroscopic physical properties has been discussed in light of recent progress in polymer dynamics to supply a better understanding about this unsaturated polyester to advance its biomedical uses. The molecular weight dependence of Tg for six polymer species including PPF has been summarized to support that Me is irrelevant for the finite length effect on the glass transition, whereas surprisingly these polymers can be divided into two groups when their normalized Tg is plotted simply against Mw to indicate the deciding roles of inherent chain properties such as chain fragility, intermolecular cooperativity, and chain end mobility.     

Solution properties of targacanthin (water-soluble part of gum tragacanth exudate from Astragalus gossypinus)

Solution properties of tragacanthin (the water-soluble part of gum tragacanth) were studied by gel permeation chromatography (GPC) combined with multi-angle light scattering and viscometry at 25 degrees C. Photon correlation spectroscopy was used to determine the hydrodynamic radius. Ultrasonic degradation was applied to obtain biopolymer fractions of different molecular weights. The dependence of intrinsic viscosity [eta] and radius of gyration (s2)z(1/2) on weight average molecular mass M(w) for this biopolymer were found to be [eta] = 9.077 x 10(-5) M(w)(0.87) (dL g(-1)) and (s2)z(1/2) in the range of M(w) from 1.8 x 10(5) to 1.6 x 10(6). The conformational parameters of tragacanthin were calculated to be 1111 nm for molar mass per unit contour length (M(L)), 26 nm for persistence length (q) and 1.87 ratio of R(g)/R(h). It was found that the Smidsr?d parameter B, the empirical stiffness parameter was 0.013, which is lower than that of several polysaccharides indicating the stiff backbone for tragacanthin. The rheological behavior of aqueous solutions of gum tragacanth and its insoluble and soluble fractions (bassorin and tragacanthin, respectively) were studied. For concentrations equal to 1%, at 25 degrees C and in the absence of salt, bassorin solution showed the highest viscosity and shear thinning behaviour. Power law and Williamson models were used to describe the rheological behaviour of bassorin and tragacanthin, respectively. Oscillatory shear experiments showed a gel like structure for the bassorin but for tragacanthin the oscillatory data were as would be expected for semi-dilute to concentrated solution of entangled, random coil polymers. NaCl changed the steady and oscillatory rheological properties of both fractions and in this way the final viscosity of bassorin was even less than tragacanthin. The calculated activation energy for bassorin and tragacanthin indicated a more rapid decrease in viscosity with temperature for tragacanthin. The plot of eta(sp,0) versus C[eta] revealed that the transition from dilute to semi-dilute regime occurs at C*[eta] = 2.82 for tragacanthin.     

Structural characterization, degree of esterification and some gelling properties of Krueo Ma Noy (Cissampelos pareira) pectin

Pectins extracted from Krueo Ma Noy (Cissampelos pareira) leaves mainly consisted of galacturonic acid with trace amount of neutral sugars. The dominant structure of Krueo Ma Noy pectin was established as a 1,4-linked -D-galacturonan by a combination of carboxyl reduction and methylation analysis, and confirmed by FT-IR spectroscopy. The degree of esterification of Krueo Ma Noy pectins was 41.7 and 33.7% for crude and dialyzed pectins, respectively. Krueo Ma Noy pectin has an average molecular weight of 55 kDa, radius of gyration of 15.2 nm and intrinsic viscosity of 2.3 dl/g. Krueo Ma Noy pectin exhibited gelling properties in aqueous solutions at 0.5% (w/v) at 5 °C. Gels were formed at concentrations of 1.0% (w/v) and above even at room temperature. The gel strength, melting point, and melting enthalpy of Krueo Ma Noy pectin increased with polysaccharide concentration.     

On the molecular weight of pectic substances and its relation to their gel strengths

A study has been made on the possibility of determining the molecular weight M_w, the second virial coefficient A₂ and the radius of gyration by measuring the light scattering of pectin aqueous solutions. The experimental data were processed on a computer by using an algorithm, accounting for the effect of microgel formations in the pectic solution. A tendency towards a decrease in M_w when decreasing the degree of esterification for a certain type of pectin was established and was confirmed by the change in the intrinsic viscosity [η]. This fact is explained by degradation during deesterification.

The dependence of the gel strength of the pectic preparations on their degree of esterification, molecular weight M_w and purity (p%) was also studied as well as the dependence of the gel strength on the intrinsic viscosity [η], the degree of esterification and the purity p%. The passive multifactor experiment method was used to obtain regression models which were tested for an optimum in the factors influencing the gel strength. The optimal value for the degree of esterification was obtained at 57–58% which confirmed the view that within this range the pectin macromolecules possess maximum conformational flexibility.     

Mapping of quantitative trait loci controlling barley flour pasting properties

Pasting properties are important characteristics of barley starch from a processing standpoint. A shorter time to peak viscosity and lower pasting temperature are favorable to both malting and food processing. This study was conducted to identify quantitative trait loci (QTLs) determining pasting properties of barley flour using a doubled haploid population of 177 lines from the cross between six-rowed Yerong and two-rowed Franklin. Yerong is a feed barley with a longer time to peak viscosity and a higher pasting temperature than the other parent Franklin which is a malting barley. Field trials were conducted in three different sites/years. Seven different parameters representing the pasting properties were measured using a Rapid Visco-analyser (RVA). DH lines showed significant differences in all seven parameters in most of the sites/years. For example, the pasting temperature of different DH lines ranged from 73.8 to 89.5 in 2006/2007 MTP field trial. Twenty one QTLs were associated with flour pasting properties. These QTLs were distributed on 11 chromosome regions. Genetic variance explained by these QTLs varies from 4.4 to 15.2%. The most important QTLs controlling the time to peak viscosity and pasting temperature were located on 1H, 2H, 3H and 7H. Results showed that some of the pasting properties can be effectively selected by the combination of several molecular markers.     

Relationship between Molecular Weights of Pectin and Hypocholesterolemic Effects in Rats

Hypocholesterolemic activities and other properties of three different molecular weight pectin were examined. The low-molecular-weight pectin (M_r ≒ 66,000) obtained by decomposition of original pectin (M_r≒ 750,000) had the properties of low viscosity and high solubility, but it lost hypocholesterolemic activities in rats. On the other hand, the medium-molecular-weight pectin (M_r ≒ 185,000) had characteristics of both low viscosity and hypocholesterolemic activities.     

Calculation of viscometric constants, hydrodynamic volume, polymer-solvent interaction parameter, and expansion factor for three polysaccharides with different chain conformations

The viscometric constants, K and a, for three polysaccharides: hydroxyethylcellulose (HEC); hydroxypropylcellulose (HPC); and chitosan, were calculated at 30 degrees C using intrinsic viscosity, [eta] and molecular weight (M(n), M(w), M(z)) data. The polydispersity correction factor, q(MHS), and hydrodynamic volume for each polymer sample were also calculated. The value of q(MHS) for the polymer samples was taken into account in the calculation of the viscometric constants. The polymer-solvent interaction parameters for the three polysaccharides were estimated by both semiempirical and numerical methods using intrinsic viscosity and molecular weight data. Hydrodynamic expansion factors were also estimated using the latter data. The quality of the solvents for the three polymers was compared using exponent a, polymer-solvent interaction parameter, and expansion factor data. This study resulted in the following constants for: The values of 0.60, 1.08, and 0.885 for exponents a indicate that HEC, HPC, and chitosan behave as a flexible random coil, linear and extended conformations, respectively. The values of exponents a for the three polysaccharides appear to be inversely related to their K values. The results of the expansion factor were consistent with the results of exponent a and polymer-solvent interaction parameters.     

Molecular characterisation of soybean polysaccharides: an approach by size exclusion chromatography, dynamic and static light scattering methods

Water soluble polysaccharides from soybean (SSPS) have a pectin-like structure and are used as stabilisers in acidified beverages. Physicochemical properties such as structure, molecular weight and shape or conformation are primary factors controlling their functional properties. Two soybean polysaccharides, a native SSPS and a modified SSPS treated with beta-(1-->4)-D-galactosidase (GPase/SSPS) were studied by dynamic and static light scattering (DLS, SLS) and size exclusion chromatography (SEC). Consecutive filtrations using a range of membrane pore size removed a small fraction of macromolecular aggregates from dilute polysaccharide solutions with relatively little effect on the major component molecules as monitored by DLS and SEC measurements. Access to aggregate-free dilute solutions of SSPS and GPase/SSPS allowed the direct measurement of molecular characteristics. SLS results showed that SSPS had a weight average molecular weight of (645+/-11)x 10(3)g/mol and a radius of gyration, Rg, of (23.5+/-2.8)nm. By comparing R(g) with the hydrodynamic radius, Rh (21.1+/-0.5 nm) obtained from DLS, the structural parameter rho (Rg/Rh) was found to be 1.1, suggesting that SSPS has an overall globular shape due to a highly branched structure. The modified SSPS had a significantly lower molecular weight (287+/-18)x 10(3)g/mol but a similar radius of gyration (23.2+/-1.7 nm). The structure parameter rho of GPase/SSPS was higher (rho=1.3) because of a smaller hydrodynamic radius (17.7+/-1.8 nm). This suggests that GPase/SSPS has a much less branched structure yet still differs significantly from a linear random coil conformation (rho=1.7-2.0). The results derived from SLS and DLS are in agreement with the conclusions obtained from a chemical analysis where the reduction of molecular weight of GPase/SSPS was caused by the cleavage of galactan side chains.     

Characterization of hop pectins shows the presence of an arabinogalactan-protein

Hop pectins were extracted from spent hops using acid extraction conditions and were characterized chemically. The acid extraction of spent hops resulted in a yield of 2%, containing 59% of polysaccharides. The hop pectins under investigation had a relatively high molecular weight and an intrinsic viscosity comparable to that of commercially available apple and citrus pectins. The low degree of methyl esterification of these pectins implicates that they are mainly suitable for use in calcium gels. The degree of acetylation and the neutral sugar content were relatively high.

A high molecular weight fraction which contained arabinogalactan-proteins was shown to be present in the hop pectin extract after preparative size-exclusion chromatography. Additionally, a fraction with a lower molecular weight was present containing mainly homogalacturonans. The arabinogalactans in the high molecular weight population consisted of (1→3)- and (1→3,6)-linked galactans highly branched with arabinose and galactose side-chains. The protein part of the arabinogalactan-protein (13%) was found to be rich in cystein, threonin, serinin, alanin, and hydroxyprolin. The molecular weight distribution of the hop pectin after degradation with the enzymes endopolygalacturonase plus pectin methyl esterase suggested that the arabinogalactan-protein present in the hop pectin extract was linked to the pectin and that the arabinogalactan-protein itself had a fairly low molecular weight.     

Rheological properties of guar gum and hydroxyethyl guar gum in aqueous solution

The rheological properties of aqueous solutions of guar gum (GG) and hydroxyethyl guar gum (HEG) have been investigated. The flow properties of these polysaccharide solutions were studied at the shear rate in the range 1.5–1310s⁻¹ using a Rheotest-2 viscometer. The flow of these polysaccharide solutions was described by equation of state based on Cross model. The basic rheological parameters, like zero shear rate viscosity (η_o), elasticity modulus (G_o) and relaxation time (gl_o) were calculated using simple and established relations. Master viscosity curves indicated that the molecular weight distribution of native guar gum has been changed by hydroxyethylation under specified reaction conditions. The effect of concentration and temperature on η_o and λ_o has been studied, and the relations among these were established by simple equations.     

Hydrodynamic properties of oxidized extracellular polysaccharides from Erwinia chrysanthemi spp

The molecular weights of the native polysaccharides of Erwinia chrysanthemi strains range from 1.8 to 7.1 x 10(6) and their hydrodynamic properties are those of polydisperse, polyanionic biopolymers with pseudoplastic, non-thixotropic flow characteristics in aqueous solutions. The effect on the hydrodynamic properties of the polysaccharides by adding carboxyl groups to increase the charge density is studied, with particular reference to their molecular weight (MW), viscosity and conformation. In general, it is found that periodate oxidation of the extracellular polysaccharides of E. chrysanthemi strains, Ech9Sm6 and Ech6S+, introduces little change in the hydrodynamic properties of the resulting polyaldehydes. However, bromine oxidation at neutral pH of the polyaldehydes results in polycarboxylate biopolymers that show significant reduction in MW and viscosity, but they are still characteristic polyanions.     

Dilute solution properties of Balangu (Lallemantia royleana) seed gum: effect of temperature, salt, and sugar

The interaction between hydrocolloids and solvent/cosolutes are the predominant factors determining their functional properties in food systems. In this research, the influence of different temperatures, salts and sugars were investigated on some molecular parameters of Balangu seed gum (BSG) as a new potential source of hydrocolloid. The results revealed that BSG has a high molecular weight (3.65 × 10(6)g/mole) and intrinsic viscosity (7236.18 ml/g), rather flexible chain with a chain flexibility parameter of 1156.53, low stiffness parameter (0.346 for Na(+) and 0.507 for Ca(2+)) and hydrogel content (46%). It was observed that except for water, the solutions of different salts (NaCl and CaCl(2)) and sugars (sucrose and lactose) are poor solvents for BSG as indicated by a monotonous decrease in intrinsic viscosity, swollen specific volume, shape function, hydration parameter, and coil dimensions. The parameters representing the interactions of BSG molecules with different cosolutes, i.e. hydrogel content and Huggins constant, were observed to increase significantly as the ionic strength and sugar concentrations increased from 0.005 to 0.05 M and 2.5 to 40% w/v, respectively. In addition, the elevated temperatures (20-50 °C) induced a clear contraction in BSG dimensional and shape parameters along with a decrease in solvent quality and the extent of associated water molecules through hydrogen bonds and/or physical entrainment. These results may be of high significance when considering the influence of major additives generally used in food products, such as various salts and sugars, and/or frequent processing parameters like temperature on rheological and functional points of view.     

On the interchain associations in aqueous solutions of a succinoglycan polysaccharide

Formation of interchain associations between succinoglycan chains have been studied by comparing weight average molecular weight, intrinsic viscosity of succinoglycan as a function of the conditions to prepare the solutions (polymer concentration, the heating temperature adopted compared with T_m). The different solutions obtained were characterized by their Newtonian viscosity, the storage and loss moduli and their sensitivity to the temperature. It was found that interchain associations, first stabilized mainly during the disorder-order transition convert to more stable associations by aging at temperatures below but not too far from T_m. These associations appear from succinoglycan solutions characterized by an overlap parameter higher than about 8 and modify only very slightly the conformational transition parameters obtained from microcalorimetry measurements.     

Viscoelastic behavior of fractionated ovine submaxillary mucins.

Solution properties of fractionated ovine submaxillary mucin (OSM) and asialo OSM (aOSM) in aqueous guanidine hydrochloride have been investigated using light scattering and rheological methods. For the first time we present viscometric evidence in both dilute and concentrated solution that the molecular structure of OSM is that of a wormlike chain. The intrinsic viscosity shows molecular weight dependence consistent with the linear extended chain conformation observed by light scattering measurements. The viscoelastic behavior of the OSM fractions in aqueous guanidine hydrochloride was further examined above the overlap concentration as a function of molecular weight and temperature. Under these solvent conditions in which the role of nonbonding intermolecular interactions is minimized, OSM shows predominantly fluid like behavior. However, high molecular weight OSM shows evidence of the existence of an entanglement network at high concentration. The frequency-dependent shear storage and loss moduli at all concentrations and molecular weights can be scaled to yield a master curve by incorporating typical viscoelastic shift parameters. The entanglement molecular weight and concentration are consistent with literature data for extended, semiflexible wormlike chains. The behavior of aOSM is similar to that of intact OSM at comparable degrees of coil overlap, indicating that the terminal sialic acid residue on the carbohydrate side chain has no effect on the rheology of concentrated OSM solutions beyond that due to an increase in the hydrodynamic volume.     

New, partially hydrolyzable synthetic analogues of lecithin, phosphatidyl ethanolamine, and phosphatidic acid

The synthesis of two new synthetic analogues of lecithin, two of phosphatidyl ethanolamine ("cephalin"), and one new phosphatidic acid analogue is described. They comprise one of each of the following types: the "isosteric" diether lecithin and cephalin analogues ROCH(2)CH(OR)- CH(2)CH(2)P(O) (O(-))OCH(2)CH(2)N(+)R'(3) (R = C(18)H(37); R' = H or CH(3)); and the "hydrocarbon" analogues of phosphatidic acid, lecithin, and cephalin, C(17)H(35)CH(2)CH(C(18)H(37))CH(2)P(O)(R) = (R'); [R = R' = OH; R = O(-), R' = OCH(2)CH(2)N(+)(CH(3))(3); and R = O(-), R' = OCH(2)CH(2)N(+)H(3)]. Infrared spectra and other properties of these compounds are described.