Extraction of polysaccharides from brown algae: rheological studies

Various species of polysaccharides were extracted from algae collected from the west coast of Morocco. This area is known for its abundance of various species of algae. The polysaccharides of three species, Sargassum muticum, Cystoseira myriophylloides and Cystoseira baccata were selected and their rheological properties were evaluated at different concentrations (1, 3, 5, 7 and 9% by w/v) and in the temperature range from 10 to 60 °C. FTIR analysis of these polysaccharides was also carried out to identify the functional groups and its analysis revealed the presence of uronic acid groups. These polysaccharides showed non-Newtonian behavior. The evolution of the apparent viscosity as a function of shear rate was described by the power-law model. The values of the flow behavior index were less than unity at high concentration. The consistency coefficient greatly increased. The non-linearity was increased with concentration and it was characterized by a power law, basically for Cystoseira myriophylloides and Cystoseira baccata. Besides, the flow behavior temperature dependence was characterized by the Arrhenius model to extract the activation energy. The values of the activation energy were found between 11.28–13.76 kJ/mol, 15.29–17.67 kJ/mol, and16.83–17.98 kJ/mol for Sargassum muticum, Cystoseira baccata and Cystoseira myriophylloides, respectively.