|Tilley, Michael - Mike|
Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2010
Publication Date: 8/15/2010
Publication URL: http://dx.doi.org/10.1016/j.foodchem.2010.01.008
Citation: Wang, F., Wan, J., Huang, W., Tilley, M. 2010. Effects of Transglutaminase on the Rheological and Mixolab Thermomechanical Characteristics of Oat Dough. Food Chemistry. 121(4):934-939. Interpretive Summary: The bread bakery industry is increasingly using frozen dough, which is preferred for manufacturing and standardization of product quality. The phase change of water and the recrystallization of ice during frozen storage of dough are important parameters that determine the quality of bread products. Water also plays a critical role in staling of bread made from frozen dough due to the formation of ice crystals. Glycerol application to frozen dough has been demonstrated to improve the anti-freezing property of yeast, similarly, ice-structuring protein (ISP) improved the specific volume and softened the bread crumb of frozen dough bread. However, the effects of cryo-protectors such as glycerol and ISP on water mobility in frozen dough and bread are not well known. Nuclear magnetic resonance (NMR) is one of the most powerful techniques for determining changes in water mobility and molecular interactions. The changes of water state in frozen doughs were studied by NMR. It was found that several NMR parameters correlated with the firming process in bread crumb. Water mobility in frozen dough and bread during storage, and the influence of glycerol, ISP, and their combined use on the physico-chemical properties of frozen dough and the staling process of bread were investigated. In general, glycerol has a greater ability to associate with water in a dough system. ISP also can reduce the water mobility of frozen dough. NMR relaxation parameters of frozen dough could be used as a powerful tool to inspect and guide frozen dough production.
Technical Abstract: To understand the effect of cryo-protectors on water mobility in frozen dough and bread during storage, transverse relaxation (T2) of protons was measured inside the magnet of a pulsed, low field 1H nuclear magnetic resonance (NMR) instrument. Using NMR, the three-component model was found to represent the states of water in the frozen dough and bread crumb samples well. The results showed that the amount of T23 state water in the frozen dough increased with time, indicating: the capability of holding water in a frozen dough system decreases with increased storage time, glycerol has a greater ability to associate with water in the system, and ice-structuring protein (ISP) can reduce water mobility of frozen dough. During bread staling, changes in T2s and the corresponding intensities of protons were complicated, suggesting a dynamic structural transformation of macromolecules and microscopic migration of moisture in the staling bread. Added glycerol showed retarding of bread staling.