Solid–liquid transitions in the rheology of a structured yeast extract paste, Marmite™

The rheology of Marmite™, a popular yeast extract spread, was studied using a range of techniques. Steady-state data indicated a structured, thixotropic material at ambient temperature; the extent of breakdown and restructuring exhibited a dependence on both stress and strain. At higher temperatures the extent of thixotropy decreased and behaviour approached Newtonian. Non-steady-state data indicated a period of shear-thickening at shear rates below those at which shear-thinning occurs. Creep tests indicated a transition between solid and liquid regimes at a critical stress that is a strong function of the solids content of the sample. A ‘true’ yield stress was not found although this may be related to the limits of the region which could be accessed experimentally.