Molecular Diffusion in Polysaccharide Gel Systems as Observed by NMR

The diffusion coefficients D of dendrimers in agar gel and pullulan in gellan gel were determined by pulsed field gradient spin-echo (PFGSE) NMR measurements. The ratio of D to D 0 (diffusion coefficient in dilute solution) was used to estimate mesh size. The mesh size increased as the temperature fell below the gelling temperature, suggesting that the solute polysaccharides are involved in aggregation. Changes in mesh size explain the experimental results of water exudation from a stored agar gel under compression and the heat resistance of gellan gel in the presence of divalent cations.