Thermal expansion of flour-water dough measured with a dynamic mechanical analyzer

Thermal expansion of a wheat flour-water dough was measured with a dynamic mechanical analyzer (DMA) at a temperature scan range of 25 to 160 degrees C, in 5 degrees C/min increments. Dough water-absorption levels were increa sed from 50 to 70% (14% mb) in 4% increments. A standard bread-baking metho d was used, and loaf volume was measured for regression analysis. The therm al expansion pattern of flour-water dough during heating included four stag es with changes in the thermal expansion coefficient: gas thermal expansion (GTE) (25-60 degrees C), starch gelatinization-gluten matrix formation (GM F) (60-100 degrees C), vapor pressure expansion (VPE) (100-120 degrees C), and structure fixation-crust formation (SCF) (>120 degrees C). The onset te mperature (T-o) between each stage and the thermal expansion coefficient (C -e) of each stage were affected significantly by dough water content. The o nset temperature (To1-2) from GTE to GMF (the starting temperature of gelat inization of starch in dough) decreased from 68 to 55 degrees C as water ab sorption increased from 50 to 70%. The thermal expansion coefficient (C-e2) of flour-water dough during GMF was highly correlated (r(2) = 0.886) to br ead loaf volume. The ratio (C-e2/C-e1) of thermal expansion coefficient dur ing the GMF stage to the coefficient during the GTE stage also was signific antly correlated (r(2) = 0.882) to baking volume. Thus. DMA measurement of dough thermal expansion has the potential to be a powerful method of predic ting baking quality in cultivar screenings, baking simulations, and scale-u p studies.