Study of water in dough using nuclear magnetic resonance

The amount and state of water play an important role in the preparation and properties of wheat flour doughs and their products. A new method for pres entation and analysis of relaxation time measurements of protons in dough i s described in this article. This new method acknowledges a continuous prob ability distribution of protons having different relaxation times in hetero geneous systems such as dough, which is dramatically different from the con ventional discrete methods that rely on prior assumptions of a number of di screte relaxation components. In the present study, pulsed proton nuclear m agnetic resonance was used to study the relaxation characteristics of dough systems at moisture levels of 12-45%. The relaxation curves obtained using a 90-degree pulse (Onepulse) sequence and the Carr-Purcell-Meiboom-Gill pu lse sequence were analyzed using a multiexponential discrete model and a co ntinuum model. The discrete model produced three fractions of protons relax ing in three different time domains. The continuum model produced spectra o f spin-spin relaxation time vs. amplitude, from which two to five peaks, de pending on the moisture content, could be identified. At moisture contents of 23 and 35%, dramatic changes in relaxation time and amplitude were obser ved with both models. The continuum model provided additional information a bout the homogeneity of the morphology and physical state of the dough syst ems.