NMR investigation of the dynamic behaviour of guar galactomannan water solutions

Proton longitudinal and transverse relaxation times have been measured to examine the concentration dependence of the dynamic behaviour of guar galactomannan aqueous solutions. Two concentration regimes have been evidenced from our results, with a limiting concentration separating the two regimes at about 3% guar concentration. The T1/T2 ratio indicates that even bulk water experiences anisotropic motions over the limiting concentration. A comparison is made with T1/T2 ratios evaluated in glucose solutions which do not exhibit any deviation from isotropic behaviour of bulk water molecules. The results are discussed taking into account topological entanglement interactions between polysaccharide molecules, according to the current model for the solution behaviour of guar galactomannan.