Rheological behaviour of baker’s yeast suspensions Original Research Article

By using a few rheometrical instruments (such as a conventional rotational viscometer equipped with a double couette sensor system; a dynamic stress rheometer with cylindrical and plate-and-cone geometry, and Cannon–Fenske capillary viscometers), it was possible to assess that yeast suspensions in the range 25–200 kg m−3 behaved as Newtonian liquids. In fact, their dynamic viscosity (as determined under shear flow, oscillatory flow and creep) practically coincided with that determined using capillary viscometers. The relative viscosity of these suspensions at 5°C was then correlated to the yeast volumetric fraction (φ) by means of the Krieger equation, while the effect of temperature on viscosity was better described by using a power-law model rather than the Arrhenius relationship, its empirical parameters being dependent on yeast concentration.