PULSED-FIELD GRADIENT SPIN-ECHO NMR MEASUREMENT OF WATER DIFFUSION-COEFFICIENT IN THICKENING AND GELLING AGENTS - GUAR GALACTOMANNAN SOLUTIONS AND PECTIN GELS

The Pulsed Field Gradient Spin-Echo (PFG-SE) method was used to study the diffusional properties of water in guar galactomannan solutions an d in highly methyl-esterified (HDE) pectin solutions and gels. The dif fusion coefficient of water in the non-gelling galactomannan system wa s the same than that of pure water and independent on polymer concentr ation, despite of a strong increase in viscosity. In the two-component gelling system, pectin-sucrose, the diffusion coefficient of water wa s lower than in the pure state, and decreasing as a function of the co ncentration of both constituents. A normalized diffusion coefficient, D-gel/D-suc, was defined to discriminate the effect of the gelation pr ocess on water diffusion, and it showed a clear dependence on the exte nt of network formation. Unrestricted diffusion was evidenced in all c ases.