KINETICS OF ION-INDUCED GELATION IN CARRAGEENAN GELS UNDER PHYSIOLOGICAL CONDITIONS

The kinetics of gelation of an ungelled carrageenan solution exposed t o a gel-inducing ionic solution was studied using a turbidity techniqu e. Alkali metal ions were allowed to diffuse through a dialysis membra ne into the solution of biopolymer. Optical transmission was measured as a function of distance away from the membrane. In the early stage o f 12 h, the transmission increases with distance. After 96 h, the tran smission is independent of distance. This indicates that gelation is c ompleted everywhere inside the gel and the gel's structure is homogene ous, in agreement with previous results. Time-dependent transmission i ndicates the presence of two relaxation processes occurring during ion -induced gelation: a primary relaxation process related to the gelling zone movement, and a secondary relaxation process related to local di ffusion of polymer, bound ions, and water molecules. (C) 1996 John Wil ey & Sons, Inc.