Diffusion phenomena during the decaffeination of coffee beans

Abstract

The coffee bean behaves with respect to the diffusion of caffeine almost as perfectly as a spherical model system. This behaviour is a consequence of at least two opposite effects-the taking up of solvent and the water loss. The overall change of the diffusion coefficient caused by these factors remains, however, small compared with the shifts brought about by the parameters investigated: water content and temperature. It is therefore reasonable to express the effects of these variables by using a single quantity, namely, the average apparent diffusion coefficient which, for Columbia and Robusta coffee and at optimal experimental conditions, lies in the range 0·5-1·3.10-6 cm2 sec-1. © 1979.