Rheology of edible soft glassy materials

In this paper we investigate the rheology of three different classes of edible yield stress fluids: a) cookie doughs, b) vegetable/fruit purees, and c) protein-rich doughs as used in meat analogs and 3D food printing. Strains sweeps of different formulations within one class can be mapped to a (partial) master curve, with at least the same strain softening index, and a similar crossover point. For classes showing only a partial master curve, the formulation differs in the response of the loss modulus in the linear viscoelastic (LVE) regime, and the transition regime between LVE and strain softening regimes, where several formulations also show a weak strain overshoot. Amongst different classes, different behaviour in strain softening has been observed. Meat analogs and fruit purees show a ratio of 2 between strain softening indices of elastic and loss modulus, while for cookie doughs and protein-rich inks, the ratio is near unity. A constitutive model using a configurational tensor with shear rate-dependent viscosity and strain-dependent elastic modulus can reproduce all features observed for the different classes and for the various formulations within a class. We conclude that our constitutive model is a good basis to design edible yield stress fluids for fiber-enrichment, starch and/or sugar replacement.