Water mobility in wheat flour doughs and breads was investigated by deuteron relaxation using pulsed NMR. Water was replaced by deuterlum oxide in dough and bread at different concentrations. Mixograms indicated that wheat flour associated more strongly with D20 than it did with H20. Varying the D2O:HzO ratio of flour doughs had no effect on the longitudinal (Tt) or transverse (Tz) relaxation times of deuteron. Hard wheat and soft wheat flour doughs showed similar increases in Tt and T2 with increasing moisture content. Staling of bread crumb was accompanied by decreased Tt and T2, indicating an overall decrease in water mobility and increase in water binding. The decrease in water mobility of bread crumb with storage time was shown to be independent of reduction in moisture content.

Transverse relaxatioh time (T,) of water protons in wheat flour doughs, an indication of moleculdr mobility of water, was determined by pulsed nuclear magnetic resonance. The relaxation curves consist of two components with a long and a short T, , corresponding to a more mobile and a less mobile fraction, respectively. The less mobile fraction has a T, of about 20 msec and accounts for about 0.62g water per g dry solid. These values seem to be independent of flour strength and mixing time. The more mobile fraction increased with moisture content and showed T, value of about 60 msec for most samples. Mixing and addition of salt to the dough resulted in reduced T,.

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