Action of Oxidants on Water Sorption, 2H Nuclear Magnetic Resonance Mobility,and Glass Transition Behavior of Gluten

Oxidation of vital wheat gluten with potassium bromate and ascorbic acid significantly extends or broadens glassy-rubber transition to a higher final temperature range or moisture content. Thermomechanical and deuterium nuclear magnetic resonance (NMR) data show that the increased stiffness due to oxidation could be detected from the thermomechanical and deuterium NMR mobility level, indicating increased rigid fractions. The oxidation also resulted in increased water sorption, but no significant change in “freezable” water, and a much decreased mobile deuterium NMR signal. Room temperature sorption of water resulted in a glassy-rubbery transition over a ≈10–20% mc range for the control. For the oxidized sample, it started at ≈10%mc, but the transition was gradual and extended into much higher moisture ranges that corresponded to a more rigid fraction of deuterium (NMR) signal. This suggests that the oxidative interactions led to a more rigid gluten fraction, extending the transition to a higher temperature range, perhaps resulting in a more elastic dough.