The viscoelastic properties of a well-characterized exocellular polysaccharide (EPS) produced by the lactic acid bacterium Lactococcus lactis subsp. cremoris strain B40 were investigated. Dynamic rheological measurements were made as a function of frequency and EPS concentration. The bead - spring model of Rouse could reasonably describe the dynamic properties. Concentrated EPS solutions have a significant elasticity (G′ > G″) at high frequencies. The relatively high G′ values at high concentrations and high frequencies are indicative of significant normal stress differences, and we put forward a hypothesis that suggests that these normal stresses may explain the contribution of EPSs to the ropy behavior of yogurts.
Tuinier, R., Oomen, C. J., Zoon, P., Cohen Stuart, M. A., & de Kruijf, C. G. (2000). Viscoelastic properties of an exocellular polysaccharide produced by a Lactococcus lactis. Biomacromolecules, 1, 219-223. https://doi.org/10.1021/bm000282v