Molar mass and rheological characterisation of an exopolysaccharide from Pediococcus damnosus 2.6

The molar mass and rheological properties of an exopolysaccharide (EPS) from Pediococcus damnosus 2.6 were investigated. The molar mass was determined by asymmetrical flow field-flow fractionation coupled with multiangle light scattering and refractive index detection. The EPS was observed to be a flexible chain polymer with a molar mass value of 4 × 106 g mol−1. Heating the sample at 80 °C for 10 min caused a shift to lower hydrodynamic radius. The rheological behaviour of the EPS was compared to that of a commercial cereal β-glucan (0.359 × 106 g mol−1). The maximum storage modulus, Gmax′ for EPS solution was lower than that for the cereal β-glucan at all concentrations, while the relaxation time, tG′=G″tG′=G″ was higher. The Gmax′ was reduced on heating the EPS solution at 80 °C for 10 min, likely indicating some conformational changes. Three-dimensional models of the polymers revealed some differences in intramolecular hydrogen bonds. The EPS molecule had a ropy nature in solution and this could make it suitable for usage as a thickener in food systems.