Rheological Characterization of Butter Samples Using a Lubricated Squeezing Flow

The functional properties of butter, such as its rheological properties, are of primary importance for its use in many bakery applications. Here, we report on a squeeze flow method to evaluate the rheological properties of butter samples with a test that mimics the mechanical stress encountered by butter in extrusion/laminar processes. This test is performed in the lubricated mode to measure biaxial extension viscosity of small samples. The compression is performed with a constant biaxial strain rate and not with a constant crosshead speed. This allows us to determine the apparent viscosity of butter in the elongation mode. This method is particularly adapted to test butter samples at different temperatures as slippage could be a problem in the measurement of rheological properties of butter by traditional shearing methods, whereas slippage is a prerequisite in squeeze flow tests.