59D-35 |
Effect of constituents on molecular dynamics of water in dough as studied by NMR |
Y. KOU1, E. W. Ross2, and I. A. Taub2. (1) Department of Food Science, University of Massachusetts, Amherst, MA 01003, (2) OTD, U.S. Army Natick Soldier Center, Kansas Street, Natick, MA 01760-5018 The concept of a distribution of microdomains within a heterogeneous food matrix provides a basis for explaining the observed dispersion in its volume-averaged properties. Viscosity, mobility, glass transition, and reactivity that vary at the local or microscopic level are best described in terms of an average and a dispersion. Since changes can take place in regions of low viscosity, the distribution of microdomains should be considered in assessing food stability and its implication for quality and safety. The objective of this study was to assess the influence of differing levels of moisture, gluten, and starch over a range of temperatures on the molecular dynamics of water and on the distribution of microdomains in dough. Dough samples with different moisture contents and gluten levels were examined at different temperatures. A suite of NMR techniques was used to measure spin-spin relaxation times (T2), spin-lattice relaxation times (T1), and self-diffusion coefficient (D) of water. A mathematical model was applied to convert relaxation data into a spectrum of relaxation times. Analysis of T2 data discerned different proton spin environments in dough. The T2 values varied depending on the moisture and solid contents, reflecting four dominant fractions of associated water molecules. T1 and D values also varied and could be correlated to the Tg of dough. The water mobility increased with increasing moisture content and temperature, and was also influenced by the concentration of the gluten and starch. The increase in water mobility is taken to be related to structural changes involving constituents, and the changes in dispersion reflect changes in the distribution of microdomains in dough. The influence of constituent concentrations at different temperatures on the structure and distribution of microdomains provides some insight into the nature of the interactions, which can be exploited in principle for improving food quality and shelf life.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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