Plantago Ovata Husk: An Investigation of Raw Aqueous Extracts. Osmotic, Hydrodynamic and Complex Rheological Characterisation.

The aim of the study was to characterize raw aqueous extracts from Plantago ovata husk in terms of molecular chain mass, osmotic, hydrodynamic, and rheological properties. The raw extracts used in this study have not been yet investigated in the indicated research area. Determination of the molecular weight of the chains present in the extract was performed by gel permeation chromatography (GPC). Osmotic properties were characterized using membrane osmometry. Rheological properties were investigated via classical rotational rheology with normal force measurements, as well as less common but equally important measurements of extensional viscosity. Two types of chains with an average molecular mass of 200 and 1780 kDa were found. The values of the first virial coefficient (B2) indicate the predominance of biopolymer-biopolymer interactions. The hydrodynamic radius established at 25 and 30 °C was 74 and 67 nm, respectively, and lower than at 40 °C (>600 nm). The first critical concentration was determined: c*=0.11 g·dL-1. The dominance of negative normal force values resulting from the formation of a pseudo-gel structure of the heteroxylates was demonstrated. Extensional viscosity measurement results revealed that the studied extracts cannot be treated as simple shear-thinning fluids, as indicated by shear flow, but should be considered as viscoelastic fluids.

When Incorporated into Fruit Sorbet Matrix, Are the Fructans in Natural Raw Materials More Beneficial for Bone Health than Commercial Formulation Added Alone?

We assessed the extent to which fructans from various sources and added in various forms (raw materials in diet alone or incorporated into a strawberry matrix) differ in their effectiveness towards selected parameters related to bone health under calcium hypoalimentation in growing female Wistar rats. The aim of this study was to evaluate the levels of selected parameters involved in calcium metabolism, in response to a 12-week restriction of Ca intake: serum ions (Ca, Mg, P); the activity of alkaline phosphatase-using a BS 120 analyzer; the markers of bone turnover (osteocalcin, CTX; using a Rat-MidTMOsteocalcinEIA Kit and RatLapsTMEIA, respectively); and the bone mineral content (BMC) and density (BMD), using a Norland Excell Plus Densitometer. Among the examined markers, the CTX concentration increased dramatically under calcium hypoalimentation. The presence of Jerusalem artichoke (independently of the form of addition) and yacon root powder (with strawberry sorbet matrix) in the rats' diet led to a significantly lower CTX concentration than was observed in the low-calcium control group. The type of fructan influenced the bone mass content. When fructan was added to the low-calcium diet as an ingredient of sorbet, it exerted more pronounced effects on the biochemical parameters of bone metabolism than when added alone, in the growing-female-rat model.

Functional and Rheological Properties of Vicia faba L. Protein Isolates.

A protein isolate (85.5%) was obtained from the Vicia faba L. seeds. The main protein fraction, typical for the seeds of this plant, was found to be most numerous: Legumin (35 kDa) and Vicilin (45 kDa). The hydrodynamic and surface properties of isolate aqueous solutions were studied with the help of dynamic light scattering, ζ-potential, and tensometry in a wide range of concentrations and pH conditions. Selected functional properties, like foaming and emulsifying abilities, were studied. An increase of water solubility was shown with a raising pH, as well as a water holding capacity (WHC). The protein isolate showed a tendency to decrease the surface tension of water solutions, with high hydrophobicity and a negative charge of the isolate enhancing the foaming and emulsifying properties. The analysis of the concentration and the pH influence on selected functional properties indicated alkaline conditions as favorable for good foaming and emulsifying properties of the isolate and affected on their rheological properties.

Swelling of Hydrogels Based on Carboxymethylated Starch and Poly(Acrylic Acid): Nonlinear Rheological Approach.

In this paper, the authors discuss the results of research on the preparation and properties of superabsorbent hydrogels based on carboxymethylated high-amylose corn starches. They were obtained by graft copolymerisation (in an aqueous environment) of acrylic acid and its sodium salt onto modified starches (with various substitution degrees DS = 0.2 and 0.8), using potassium persulfate as an initiator and N,N'-methylenebisacrylamide (MBA) as a cross-linker. Modified starches, with various DS, were used to synthesise two series of hydrogels with varying molar ratios of cross-linkers to monomers. The swelling behaviour of hydrogels was studied and their properties were estimated using the kinetic equation. The occurrence of starch-polyacrylic acid covalent interactions was demonstrated by FTIR analysis. Nonlinear rheological methods have proved to be very effective in assessing the mechanical properties of hydrogels. LAOS (large -amplitude oscillatory shear) analysis allowed the determination of the durability of the gel structure as a function of the amount of absorbed water.

The effect of temperature on the colligative properties of food-grade konjac gum in water solutions.

This research paper presents the results of tests on the colligative properties of konjac gum chains in water solutions. For this purpose, the measurements of osmotic pressure and intrinsic viscosity of aqueous solutions, in the function of konjac gum concentration and temperature were carried out. The applied methods allowed for the determination of the second osmotic virial coefficients B2, which raised with the increase of temperature. It indicate that increase of temperature causes higher affinity of polysaccharide's chains to water. It was determined, that the osmotic average molecular mass of the konjac gum in non-purified solutions increases with temperature (1.07×105-3.80×105g×mol-1). Values of the reduced viscosity linearly increased in range 18-29dL×g for all temperatures. Received values of the Huggins constant (0.81-1.72) lead that water is poor solvent for konjac gum. The theta (θ) conditions were extrapolated for non-purified solutions - 325K (52°C), and interpolated for purified solutions - 307K (34°C). Based on the results of tests using the dynamic light scattering, the values of two main relaxation times (fast - 0.4-1.8ms and slow components - 4300-5500ms) were determined (the Kohlrausch-Williams-Watts). The obtained autocorrelation functions were characteristic for sol type systems or these which indicate a gel-like structure.

The effect of structural properties on rheological behaviour of starches in binary dimethyl sulfoxide-water solutions.

This research study analysed the rheological properties of potato amylose and potato amylopectin in binary solutions of the following water and dimethyl sulfoxide concentrations: 90% DMSO (1), 80% DMSO (2) and 50% DMSO (3), with preparation methodology involving the dissolution at the temperature of 98°C. The studies of dynamic light scattering on the biopolymer coils and the determination of main relaxation times of the solutions were carried out. For the amylose solutions, the fast relaxation phenomena are predominant. The results of the quality tests of the hysteresis loop showed, that the amylose solutions in the solvents (1) and (2) are rheologically stable and shear-thickened. The amylose solutions in solvents (3) reveal oscillatory alterations of viscosity in the time. Amylopectin solutions are characterized by 80% share of slow relaxation phenomena, very low diffusion coefficients and hydrodynamic radii in the range of 2000 nm. The amylopectin solutions are rheologically unstable.

The Physical and Linear Viscoelastic Properties of Fresh Wet Foams Based on Egg White Proteins and Selected Hydrocolloids.

The aim of this work was to evaluate the physicochemical properties of fresh foams based on egg white proteins, xanthan gum and gum Arabic. The distributions of the size of gas bubbles suspended in liquid were determined, as well as density and volume fraction of gas phase of the generated foams. Additionally, the viscoelastic properties in the linear range were measured, and the results were analyzed with the use of the fractional Zener model. It was shown, that foam supplementation with hydrocolloids considerably decreased their volume fraction of gas phase in comparison to pure egg white protein-based foams. Application of gum Arabic did not cause an increase in the size of foam bubbles when compared to pure white egg foam, whereas application of xanthan gum significantly decreased the size of the bubbles. Application of the fractional Zener model allowed to determine the relaxation times, their intensity in analyzed suspensions and also equilibrium module (Ge ). The increase in the concentration of xanthan gum resulted in the prolongation of the relaxation time and increased its intensity. Gum Arabic, when added, weakened the viscoelastic properties of the mixture as a viscoelastic solid.