ABSTRACTPulsed NMR was applied to measure the spin‐lattice (T1) and the spin‐spin (T1) relaxation times of the water adsorbed on sodium alginate, pectin, corn starch, casein and cellulose. T1was determined by means of repeated 90°‐90° pulse sequences and T2by the spin‐echo method. T1relaxation time curves for all the samples studied showed simple exponential, i.e., single phase, behavior. Plots of T1as a function of moisture content showed minima at 0.15–0.258 water/g dry matter; plots of T1vs water activity (Aw) yielded minima at Aw of 0.65. T2relaxation time curves for corn starch containing more than 0.56g water/g DM exhibited two‐phase behavior, indicating the existence of two water fractions of different mobility. The amount of water in the bound fraction showed a remarkable consistency (0.194 ± 0.011g water/g DM) among six samples of high moisture content. T2was found to increase with moisture content for all the macromolecules. Cellulose showed exceptionally long T2values compared to the other materials at the same moisture content, whereas pectin and sodium alginate showed short T2values. These results indicated that T2value is a measure of strength of water binding. Break points were observed in the T2‐moisture curve. The moisture contents at these points corresponded to the bound water content determined by freezing and to the equilibrium moisture content at Aw of 0.9. T2increased expon
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