Abstract
Dietary fibers were evaluated for their hydration ability by the pulsed NMR method. Each dietary fiber was classified by the shape of the relaxation curve, the correlation coefficient of a linear expression for the natural logarithm of signal amplitude vs. delay time, the spin-spin relaxation time (T2), the ratio of the proton population of relaxing components, and the root mean square (RMS) value. Each dietary fiber was examined to ascribe its hydration behavior to the related polar groups.
Water-soluble dietary fibers (SDFs) had a greater correlation coefficient for any range of delay time and higher ratio for the slowest-relaxing component than water-insoluble fibers (IDFs). The relaxation curve tended to change at 30°C after one day for SDFs only, and the longest relaxation time for SDFs was less than for IDFs. The relaxation curves appeared to be monophase for most types of SDF, and multiphase for IDF. Judging from the common position of the polar groups involved in the molecule, the 6-carboxylate group seemed to contribute most to the hydration behavior of the polysaccharides. In addition, the Na form of the dissociable group tended to give more hydration ability to the polysaccharides than did the corresponding H form.
