Malvern Instruments

Analytical Solutions for Manufacturing Productivity

Evaluating product texture using oscillatory testing on a rotational rheometer

Malvern Instruments

Formulating products to have both the correct functional and sensory attributes can be a difficult task. The latter in particular relies heavily on user feedback which can take considerable time and effort to attain. In addition it is not always easy to interpret such feedback in the context of material properties and hence rheological data.

To use rheology as a tool for evaluating product texture it is important to understand which rheological test mode best mimics the particular application and also the most appropriate parameters to use in that test. For instance skin cream application and rubbing is a high shear rate process which is best evaluated using steady shear testing at the appropriate shear rate. Conversely in the pot texture is related to the underlying microstructure which is best evaluated by means of oscillatory testing or creep testing.

A simple test to evaluate material texture under small deformations is an oscillation amplitude sweep. This can provide important information relating to sample stiffness, springiness, structural strength and deformation. Stiffness is reflected in the complex modulus G* with higher values indicating a stiffer structure, while phase angle d indicates the degree of elasticity and hence springiness of the structure.

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