RHEOLOGICAL BEHAVIOR OF ERWINIA GUM IN AQUEOUS SOLUTION

摘要

Erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose andglucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and arotational viscometer. Its weight-average molecular weight M_w and intrinsic viscosity [η] in 0.2 mol/L NaClaqueous solution were measured by light scattering method at 35℃and viscometry at 25℃and found to be1.06×10~6 g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gelpermeation chromatography (GPC). These results indicated that E gum in water has exceedingly highviscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreasedwith increasing temperature, and the turning point appeared at 38℃for dilute solution and 80℃forconcentrated solution suggesting that the aggregates of E gum in water started to disaggregate under thesetemperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimentalresults indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.