EFFECTS OF SUCROSE, GLUCOSE, UREA AND GUA NIDINE-HYDROCHLORIDE ON THERHEOLOGICAL PROPERTIES OF GELLAN GUM GELS

Effects of sucrose, glucose, urea and guanidine hydrochloride on dynam ic elasticity of gellan gum gels, with and without potassium chloride or calcium chloride, were studied. The dynamic Young's modulus E' of g ellan gum gels without and with the salts decreased with increasing co ncentrations of sucrose or glucose. Urea weakened the gelling ability by breaking hydrogen bonds: Urea strengthened the gel-forming ability of gellan gum gels containing excessive potassium chloride or calcium chloride. Guanidine hydrochloride promoted the gel-forming ability by the aggregation of double or single helices of gellan gum molecules, u p to a certain amount, but excessive addition of guanidine hydrochlori de weakened the gelling ability of gellan gum gels with and without po tassium chloride. Guanidine hydrochloride weakened the gelling ability of gellan gum gels with calcium chloride. It is suggested that a smal l amount of guanidine hydrochloride shields the electrostatic repulsio n between carboxyl groups in gellan gum molecules and increases the nu mber of junction zones. However, higher excessive amount of guanidine hydrochloride disrupts hydrogen bonds and weakens the gel-forming abil ity.