Viscoelastic properties of an exocellular polysaccharide produced by a Lactococcus lactis

The viscoelastic properties of a well-characterized exocellular polysacchar ide (EPS) produced by the lactic acid bacterium Lactococcus lactis subsp. c remoris strain B40 were investigated. Dynamic theological measurements were made as a function of frequency and EPS concentration. The bead-spring mod el 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 frequencie s are indicative of significant normal stress differences, and we put forwa rd a hypothesis that suggests that these normal stresses may explain the co ntribution of EPSs to the ropy behavior of yogurts.