H-2 AND O-17 NUCLEAR-MAGNETIC-RESONANCE STUDY OF WATER IN GLUTEN IN THE GLASSY AND RUBBERY STATE

Water mobility in hydrated gluten at 0-50% mc was studied using O-17 a nd H-2 nuclear magnetic resonance (NMR), Glass transition behavior mea sured by dynamic mechanical analyzer (DMA) and by differential scannin g calorimetry (DSC) was compared to the NMR signal intensity. The H-2 NMR signal intensity increased during glassy-rubbery transition due to hydration. O-17 NMR detected the signal when >0.21 g of water/g total occurred in the ''free'' or bulk water region, as determined from the sorption isotherm. Freezable water was only observed at >18% mc, when the sample was in the rubbery state (beyond the midpoint glass transi tion) and water was unfreezable in the glassy region. Results from the different techniques (NMR, DMA, DSC, and sorption isotherm) showed go od correlation, although experimental conditions, sample preparations, and the time frame of each experiment were inherently different.