Extensional rheology of bread dough

Abstract

We investigated the extensional properties of wheat flour dough on the Filament Stretching Rheometer (FISER), in which the sample approaches uniform uni-axial extension flow at a constant strain rate over a large portion of the experiment, thereby allowing us to directly probe the transient material function characterizing the behavior of dough in extension. The large dynamic range of this Rheometer permitted us to investigate the visco-elastic nature of the dough well into the baking/proofing range. Special experimental protocols and modifications to the rheometer fixtures were designed and built to overcome problems in sample preparation. Parameters such as water content, base flour type and mixing conditions were varied to determine their respective effects on the extensional properties. Ultimately we would like to develop a constitutive equation describing the evolution of stress during extension and arrive at a model for the stability against rupture in these doughs.

(cont.) This will form the basis for developing protocols to map results from the true uni-axial extension experiments onto empirical measurements obtained from existing and widely utilized industrial standard testing devices. As an example in this first stage, we focused on the Mixograph, which is a widely accepted method of testing dough in the food industry, and considered how its output can be related to the true material functions generated in filament stretching rheometry.