Rheological characteristics and chain conformation of mannans obtained from Saccharomyces cerevisiae

Mannans were extracted from S. cerevisiae, the rheological properties of mannan solutions were important in many industrial applications. In this paper, effects of mannans concentration, solution temperature, pH, salts and their concentrations on apparent viscosity were investigated. The conformational parameters of yeast mannans were determined by SEC-MALS-RI-DP. The Higiro's 1 and Higiro's 2 plots were obtained by capillary viscometry gave an intrinsic viscosity of 0.166 and 0.131dl/g. The yeast mannans solution showed Newtonian flow behavior at all the tested concentrations. The apparent viscosity of yeast mannans solution decreased continuously with the temperature increase (25°C-85°C) at a given shear rate. The viscosity did not change within the pH values of 4.0-10.0, however, it increased when the pH decreased from 4.0 to 2.0. The viscosity decreased with addition of CaCl₂ up to 10mM and remained constant above this concentration. The conformational parameters (derived from [η] vs M_w and R_g vs M_w) showed yeast mannans existed as a sphere-like shape with many shorter branches. The special flow behavior and conformation of yeast mannans may make it preferable polysaccharide in food industry.