Extraction of fat from pigskin with supercritical carbon dioxide

A supercritical fluid extraction process for reducing the fat content of pigskin is presented in this work. Carbon dioxide has been used as supercritical solvent for fat extraction. Efficiencies close to 100% were reached. The influence of process parameters - such as extraction temperature, pressure and time and solvent ratio - on the extraction yield was studied. The influence of other variables such as initial fat and water content of the pigskin was also considered. The results showed that when using pigskin sheets, for non-interrupted extractions, there was an extraction yield limit, of around 60%, that could not be overcame even using an extraction pressure of 65 MPa. Some experiments that were interrupted for sampling of the pigskin showed that there was a positive influence of the intermediate depressurizations of the extractor on the extraction yield and, in this case, values close to 100% could be reached. The analysis of the results gave rise to the conclusion that the external mass transfer resistance could be easily eliminated by increasing the solvent flow rate through the extractor. The internal mass transfer resulted to be the main resistance controlling the rate of the process, although, in the very first part of the extraction, it was the solubility that imposed the limit to the process rate. A steady-state approximation of the extraction from solids was used to model the experimental data and to obtain the total mass transfer coefficient that would allow the scale up of the process. (c) 2005 Elsevier B.V. All rights reserved.