Energetical and rheological approaches of wheat flour dough mixing with a spiral mixer

Wheat flour dough was mixed in a spiral mixer for different operating conditions, at a speed ranging from 80 to 320 rpm, for a period of 7–15 min. The specific mechanical energy Es delivered and the dough temperature Td were continuously recorded and varied from 7 to 82 kJ/kg and Td of 13.5 to 36 °C, respectively. Es and Td were strongly correlated because of viscous dissipation but variations of ingredients initial temperature allowed to uncouple them. The energy balance during mixing process was set through a simple model assuming constant heat transfer (h = 75 W/(m2 °C)) which took into account thermal losses. Shear viscosity curves of the dough were determined by correlating volumic power to angular speed; by comparison to typical dough shear flow curve, a constant characteristic of the mixer geometry (Ks = 1.55) was determined like for models of mixer power consumption. The impact of mixing on small deformation rheological properties was assessed by DMA and the variations of the ratio, of maximum (75 °C) to minimum (50 °C) elastic modulus, was interpreted in relation with gluten network development.

► Temperature and energy during wheat dough in spiral mixer show important viscous dissipation.
► Model of energy balance with heat transfer coefficient ≈75 W/(m2 °C).
► Viscosity power law model with spiral mixer constant = 1.55.
► Both constant characterize spiral mixer.
► Gluten network development assessed by thermal variations of storage modulus.