NMR velocimetry study of the temperature dependent rheology of butter, semisoft butter and margarine

A new rheological characterization technique is described in which nuclear magnetic resonance (NMR) velocimetry is used to measure velocity profiles a cross the annular gap of a Couette cell, for materials that exhibit yield s tress and power law shear thinning properties. The materials studied were b utter, semi-soft butter and margarine over a temperature range from 25C to 42C. The method enables the observation of heterogeneous behavior across th e different stress regimes that are present in the Couette gap and flow vis ualization makes it possible to clearly identify, the existence or absence of slip effects at the wall. The results show that the power law exponents are strongly temperature dependent for the edible fat materials investigate d.