NMR studies of calcium induced alginate gelation. Part II. The internal bead structure

Proton NMR relaxation, diffusion and microimaging techniques were used to i nvestigate the internal structure of calcium alginate gel beads formed by d ripping a sodium alginate solution into a calcium chloride solution. It is shown that many of the pore structures previously reported are probably art efacts of sample preparation. Evidence is presented for a non-uniform calci um alginate concentration profile even in beads that have been 'equilibrate d' in calcium chloride solution for over 24 h. It is found that the interna l structure depends on the ratio of calcium and alginate concentrations and a microstructural phase diagram can be constructed. Copyright (C) 2000 Joh n Wiley & Sons, Ltd.