KAPPA-CARRAGEENAN GELS - EFFECT OF SUCROSE, GLUCOSE, UREA, AND GUANIDINE-HYDROCHLORIDE ON THE RHEOLOGICAL AND THERMAL-PROPERTIES

The effect of sucrose, glucose, urea, and guanidine hydrochloride on dynamic viscoelasticity and differential scanning calorimetry (DSC) curves of k-carrageenan gels were studied. The dynamic Young's modulus E' and the melting point of k-carrageenan gels increased with increasing sugar content. Urea weakened the gelling ability. Guanidine hydrochloride strengthened the gelling ability up to a certain amount, but excessive addition of guanidine hydrochloride weakened the gelling ability. The heat absorbed on forming 1 mol of junction zones showed a maximum as a function of added content of sugars or guanidine hydrochloride. It is suggested that sugars may create junction zones and stabilize the structure of junction zones, but the excessive addition of sugars immobilizes free water necessary for junction zone formation. Low concentrations of guanidine hydrochloride shield the electrostatic repulsions between sulfate groups in k-carrageenan molecules and stabilize the structure of junction zones. However, higher concentrations of guanidine hydrochloride disrupt hydrogen bonds and weaken the gel-forming ability. © 1990, American Chemical Society. All rights reserved.