Anton Paar interfacial rheology system

The thin layer of froth on the surface of an espresso, known as the crema, is considered to be a sign of a good coffee. The crema comprises a dispersion of tiny gas bubbles surrounded by surfactants and emulsified oils.

Interfacial rheology does not probe the foam itself, but measures the adsorption of the amphiphilic ingredients and their network formation at the liquid-foam interface. Higher values of the interfacial properties and a faster film formation are expected to correlate with a better foam stability.

The Anton Paar interfacial rheology system (IRS) combined with an MCR rheometer enables 2-D rheological measurements of interfacial films at the air/liquid and the liquid/liquid interface. With the IRS, a bi-cone measuring system is placed in the interface and measures absorbed or spread films, eg, films produced by proteins or surfactants.

Employing the low-torque capabilities and the TruStrain feature of the MCR302/502 rheometers, the IRS enables rheological measurements of weak interfacial structures.

Measurements can be performed in rotational and oscillatory mode, eg, allowing flow curves and creep tests at an interfacial layer or oscillatory tests during the film formation process.