Rheological and Texture Studies of Butter3

Four commercial butters (conventional batch and Westfalia, Contimab and Cherry‐Burrell continuous churned) were stored at two temperatures and evaluated periodically for rheological and textural properties. Evaluation methods included four mechanical tests (quasistatic shear, quasistatic uniaxial compression, Penetrometer, and extrusion) and sensory ratings of spreadability, firmness, and other texture parameters. The first three mechanical methods produced quasistatic shear yield stress values that had close agreement. For quality control the three tests can be considered equivalent. Shear stress‐strain rate data from extrusion testing developed using the Rabinowitch‐Mooney equation could be represented well by the Casson model. Casson yield stress values were an order of magnitude lower than the quasistatic values. The power law equation with a yield stress also represented the butter flow well, and all four butters had similar power law exponents (approx. 0.56). The Cherry‐Burrell butter had much higher quasistatic and Casson model constants than the other butters. It was also the most temperature sensitive and most stable with storage time. Temperature‐shear rate equivalent effects on shear stress were demonstrated by developing shift factors. The quasistatic yield values for the butters best predicted sensory spread‐ability and hardness. The changes in flow properties (Casson yield stress and Casson slope) correlated with aging.