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Y. KOU¹, Y. Wang², and I. A. TAUB². (1) Food Science, University of Massachusetts, Amherst, MA 01003, (2) OTD, U.S. Army Natick Soldier Center, Kansas Street, Natick, MA 01760-5018

The stability of a food depends strongly on its microstructure, local viscosity, and associated molecular mobility. Moisture content, humectant concentration, and temperature are key factors that determine the structure and distribution of microdomains in dough and control local viscosity and molecular mobility.

The objective of this study was to understand the influence of moisture content, humectant, and temperature on the structure and distribution of microdomains in dough.

Dough samples with different moisture content (10 to 38%) and glycerol or propylene glycol levels (0 to 15%) were examined at different temperatures. NMR measurements were made with a PCT NMR analyzer. Single-pulse and CPMG sequences were used to measure spin-spin relaxation times (T2). Saturation recovery sequence was used to measure spin-lattice relaxation times (T1). For ESR measurements, the spin probe TEMPO was included in the samples, and the TEMPO spectrum was monitored following reduction by erythorbate.

Analysis of T2 discerned different proton spin environments. T2 values varied depending on the moisture and humectant contents. T1 values also varied and could be correlated to the glass transition temperature of dough. The reduction rate of TEMPO increased with increasing moisture content and temperature, and was also influenced by the presence of the humectant. The increase in both average water mobility and average reduction rate of TEMPO as moisture content and temperature increased was presumably related to the observed molecular and structural changes and reflected a microscopic distribution of viscosities in dough.

The results indicate the importance of hydration dynamics and its effect on microstructure in dough. A better understanding of the influence of water, humectant, and temperature on the structure and distribution of microdomains would provide a basis for improving quality and shelf life of food products.