The shear rheology of bread dough: modeling

Abstract

The mechanics and rheology of the two-regime shear flow behaviour of bread dough was explored. Small-strain oscillatory measurements revealed that storage and loss moduli data as a function of applied frequency fit power law relations, with the exponent p ∼ 0.31. A Lodge-type model with a power law memory function was then investigated for shear flow, where relaxation parameters were derived from small-strain oscillatory tests. The model implied the response to steady shear may be described as a product of shear rate to the exponent p and a function of strain, which is confirmed by experimental observations. The soft-solid rheological behaviour of bread dough under steady shear deformation was then analysed over a range of shear rates (0.1–20 s^− 1). Initially, stress was over-predicted in the reconstruction of the data, and the application of a damage function to the model was considered since the material fractures under shear strains ∼20. The damage term was found to be a function of strain over the complete range of shear rates. The transition of dough from solid-like to liquid-like behaviour is discussed, following the damage reduction factors rapidly reducing to zero post material fracture, which suggested a loss of elasticity in the dough. A simple integral-type model resulted for the prediction of the shear rheology of bread dough in the solid-like regime, with generalised Newtonian viscous behaviour predicted for shear flows following material fracture. Further analysis on local strain behaviour in more complex shearing geometry, such as tube flow, is required.