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Interfacial Shear Rheology of Coffee

Many food products are either in the form of emulsions or foams for which the knowledge of interfacial properties is important to achieve product stability.

Coffee is a complex dispersion, which in the case of espresso coffee is topped by a foam structure of tiny bubbles, e.g. the espresso cream ‘crema’. The ‘crema’ is a polyphasic system consisting of dispersed tiny gas bubbles of carbon dioxide and water vapour surrounded by surfactant films, droplets of emulsified oils, and solid fragments. Interfacial rheology does not probe the foam itself, but measures the adsorption of the amphiphilic ingredients and their network formation at the liquid surface. Higher values of the interfacial properties and a faster film formation are expected to correlate with a better foam stability. Some simple qualitative interfacial shear rheology measurements on coffee samples have been published and confirm the close correlation between foam stability and interfacial shear properties.

Different techniques have been used to measure interfacial shear properties. However, a combination of a suitable geometry with a rotational rheometer, which is both extremely sensitive in torque and angular resolution, offers the largest flexibility with respect to test possibilities and measuring ranges.

In an experiment carried out using an MCR 302 rheometer from Anton Paar rheometer and its accessories, a commercial soluble coffee powder was mixed in different concentrations with distilled water.

Click on the link above to download the five-page Application Report with all the details and interesting results of this experiment.

Anton Paar Ltd

Anton Paar develops, produces and distributes highly accurate laboratory instruments and process measuring systems, and provides custom-tailored automation and robotic solutions.

Anton Paar develops, produces and distributes highly accurate laboratory instruments and process measuring systems, and provides custom-tailored automation and robotic solutions.

It is the world leader in the measurement of density, concentration and CO2 and in the field of Rheometry. Other areas of specialty are: Viscometry, Polarimetry, Refractometry, Microwave Sample Preparation & Synthesis, Chemical and Mechanical Surface and Nanostructure Analysis.

With over 2200 employees at the headquarters in Graz (Austria) and the 25 sales subsidiaries worldwide, Anton Paar ensure that their products live up to their excellent reputation. The core competence of the company – high-precision production – and close contact to the scientific community form the basis for the quality of Anton Paar’s instruments.

A strong sales network in more than 110 countries guarantees customers rapid support and answers to their application and service queries.

Innovation is the basis for progress and every year Anton Paar invests more than 20 percent of the annual turnover in R&D.

Anton Paar Limited, a subsidiary of Anton Paar GmbH, provides sales, application support and service to users across the UK and Ireland.

With an office in St Albans (UK) and Dublin (Ireland) and a team of over 30 dedicated employees, Anton Paar Limited aims to provide first-class service at every stage in the customer relationship, ensuring our products live up to their excellent reputation.

Anton Paar Ltd
Unit F, The Courtyard
St Albans
AL4 0LA
UK

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