ABSTRACT
The rheological properties of six compound gels that consists of kappa carrageenan (KC) and another excipient such as konjac gum were explored through comparison of their viscosity measured by the rotation method. The gel fluid type was dependent on the rheological curve fitted by the power-law equation. The effect of concentration on the viscosity of different compound gels was investigated by establishing the linear equation between their viscosity and concentration, the slope of which was used to determine the relation between viscosity and concentration of different compound gels. The viscous flow activation energy (Eη) was calculated by the Arrhenius equation, which was able to investigate the effect of temperature on their viscosity. The interaction between monomer and compound gels was also studied by measuring their viscosity. The results showed that six compound gels were pseudoplastic fluid. Among all compound gels, the KC-xanthan gum (KC-XG) solution exhibited the most obvious shear thinning, the strongest pseudoplasticity, while the smallest Eη, resulting in the best thermal stability of viscosity. Furthermore, the concentration of KC-sodium hyaluronate (KC-HA-Na) solution affected its viscosity significantly. The viscosity of six compound gels was greater than the summation of the two kinds of monomer gels, which suggests that there is a synergistic-viscosity interaction between KC and another excipient.
ABSTRACT
OBJECTIVE: To investigate the rheological property of Kappa carrageenan and the effects of standing time, concentration, and temperature on the viscosity of carrageenan solution. METHODS: The fluid type was determined by fitting the rheological profiles to Power law model. The effect of temperature on the rheological behavior was investigated according to the viscous flowactivation energy(Eη) which was calculated by the Arrhenius formula. RESULTS: The viscosity of carrageenan solution decreased with the increase of shear rate and temperature, whereas it increased with the concentration. There existed a positive correlation between Eη and concentration. Furthermore, the effects of different cations on the viscosity were also studied and the results indicated that the viscosity increased significantly with the ionic concentration, especially that of potassium chloride. CONCLUSION: Carrageenan was inferred to be pseudo-plastic fluid which hasthe character of shear thinning effect and its viscosity is significantly affected by cationic species.
ABSTRACT
Agaro- and carra-oligosaccharides were produced by partial acid hydrolysis of commercial agarose and kappa-carrageenan. Di- and tetrasaccharides were purified by gel filtration chromatography and characterized by NMR (1D and 2D) spectroscopy and ESIMS. The following oligosaccharides were obtained: agarobiose, agarotetraose, kappa-carrabiose and kappa-carratetraose. Agarobiose and agarotetraose were used as standards to develop a high performance size exclusion chromatography (HPSEC) method which was utilized to study the hydrolysis rate of agarose and oligosaccharide production. Six hours of hydrolysis (0.1 M TFA, 65 ºC) produced mainly di- and tetrasaccharides. The methodology for oligosaccharide production and evaluation developed in the present work shows good potential for the production of bioactive oligosaccharides.