Cassia spectabilis DC seed galactomannan: structural, crystallographical and rheological studies

Structure of a galactomannan from the seeds of Cassia angustifolia Vahl

Cassia angustifolia Vahl (family: Caesalpiniaceae) is a fast growing and spreading Indian shrub of which seeds, pods and leaves are extensively used for pharmaceutical applications. The seeds have been found to be an alternative source of commercial gums. The structural aspects of the galactomannans have been determined for a better understanding of its properties. The purified seed galactomannan contains mannose:galactose in a ratio of 2.90. The average molecular weight (M(w)) is 9.66x10(4) and the intrinsic viscosity (eta) is 209 mL/g. Methylation analysis, periodate oxidation, Smith degradation and 13C NMR studies confirm that the gum has the basic structure of legume galactomannans with a main chain of (1-->4)-linked beta-D-mannopyranosyl units to which single alpha-(1-->6)-D-linked galactopyranosyl units are attached through block pattern.

Viscosity and temperature relationship in ethanol/water mixtures gelified with Carbopol Ultrez 10

The rheological characterization of Carbopol Ultrez 10 ethanolic (15%) gels is complemented by studying flow behavior as a function of temperature (20-50 degrees C) at different pH (4.0-7.0) and polymer concentrations (0.1-0.5%). Flow curves were adjusted to the Ostwald model, showing a fall in viscosity, together with an enhancement in flow index with increasing temperature. Calculated flow activation energies at constant shear rate (Egamma) were found to be related to the final pH of hydroalcoholic gels. Nevertheless, at the polymer concentration range evaluated, no significant correlations were obtained between activation energy and concentration. In general, the Carbopol Ultrez 10 gels exhibit little viscosity change under the temperature variations of normal use and storage, which minimizes possible unacceptable changes in the product's characteristics.

Viscosity analysis of the temperature dependence of the solution conformation of ovalbumin

The viscosity of ovalbumin aqueous solutions was studied as a function of temperature and of protein concentration. Viscosity-temperature dependence was discussed on the basis of the modified Arrhenius formula at temperatures ranging from 5 to 55 degrees C. The activation energy of viscous flow for hydrated and unhydrated ovalbumin was calculated. Viscosity-concentration dependence, in turn, was discussed on the basis of Mooney equation. It has been shown that the shape parameter S decreases with increasing temperature, and self-crowding factor K does not depend on temperature. At low concentration limit the numerical values of the intrinsic viscosity and of Huggins coefficient were calculated. A master curve relating the specific viscosity etasp to the reduced concentration c[eta], over the whole range of temperature, was obtained and the three ranges of concentrations: diluted, semi-diluted and concentrated, are discussed. It has been proved that the Mark-Houvink-Kuhn-Sakurada (MHKS) exponent for ovalbumin does not depend on temperature.