From Alveograph test to extensional behavior of wheat flour dough

Dough extensional properties obtained from 14 wheat flours hydrated at 50% (/flour weight) were assessed by the empirical test of Alveograph, a bubble inflation test, and by the rheometric test of uniaxial compression in lubricated conditions (LSF) at large deformations. In baking industry, comparison between flours is based on several parameters (n ≥ 5) defined from the alveogram, which is the time variations of pressure inside dough. In this study, the alveogram is converted into a stress-strain curve (σ = f(ε_b)). Then, from this curve, the extensional behavior coefficient of the flours, assessed by the consistency k₀, is fitted between 0 ≤ ε_b ≤ 1.5, assuming \(\dot{\varepsilon_b}\) $\dot{{\epsilon }_b}$ = 0.25 s⁻¹ (R² = 0.99 ± 0.01 for 14 flours). The flow index (n = 0.36) and strain hardening index (SHI = 1.73) are kept constant. The model is validated by comparing the stress values calculated from the alveogram to those measured in LSF for wheat flour doughs hydrated at 50% (R² = 0.91) at ε_b = 1 and 0.25.10⁻² < \(\dot{\varepsilon_b}\) $\dot{{\epsilon }_b}$ < 2.5 s⁻¹. Therefore, the Alveograph, which allows classifying flours according to several dough stretching properties, also provides access to the model of dough extensional behavior.

Determining dough extensional properties for alveograph test and validating by comparison with resutls obtained by LSF