Effect of the drying rate of bread crust on complex viscosity
Effet de la vitesse de séchage d'une croute de pain sur la viscosité complexe
Lucas, T. ; Vanin, F.M. ; Michon, C.
Type de document
Communication scientifique avec actes
Affiliation de l'auteur
IRSTEA RENNES UR TERE FRA ; IRSTEA RENNES UR TERE FRA ; AGROPARISTECHN JRU 1145 ENGINEERING PROCESSES FOOD MASSY FRA
Résumé / Abstract
Crust and crumb come from the same original dough, but their properties differ due to a distinct local heat-moisture treatment. Stiffening of crumb, but also of crust, is known to affect dough inflation and squeezing. Past studies focused on dough rheology considered at best the effect of temperature at constant dough water content. This study aimed at characterizing the effect of heat-moisture treatment on dough rheology. Dynamic mechanical thermal analysis DMTA applied to a dough strip was retained and the heating rate in the DMTA oven was varied. Temperature and water content in dough were monitored and compared in the state diagram. High heating (drying) rates (>15°C/min) were relevant of a top crust, while lower heating rates (5°C/min) were rather relevant to the bottom crust during pan baking. At high heating rates, dough viscosity behaved as if water content was kept constant and as long as temperature remained below 80°C (stage A). Conversely to high heating rates, complex viscosity at low heating rates increased with decreasing water content; this was attributed to the enhanced distribution of water at the microscopic scale. The decrease in viscosity observed above 80°C in samples at constant water content was not observed whatever the heating rate, and replaced by a long-lasting plateau (stage B); this was related to a value in water content below approximately 37%, common to all drying rates. The range of water content over which stage B took place increased with higher heating rate, possibly affecting the degree of starch gelatinization. This implied that the higher the heating rate, the lower the complex viscosity in stage C (factor of 2). Above the ebullition temperature of water, the logarithm of complex viscosity increased linearly with water content (stage C), at a rate independent on the heating rate.
Cereal & Europe, 29/05/2013 - 31/05/2013, Leuven, BEL