In this work, an extraction model capable of predicting the supercritical extraction process of seed oil is presented. The model bridges the 'broken and intact cells' and the 'shrinking-core' models available in the literature: as the former, the proposed model takes into account the seed structure with the presence of oil-bearing cells; as the latter, it assumes that the particles progressively exhaust their oil content from the outside to the inside, with a core shrinking during the process. The internal mass transport coefficient is described with three alternative models: the discrete and the semi-continuous models are superior to the continuous one which undervalues the same coefficient. By means of a supercritical extraction-column model and utilizing several experimental data of supercritical grape-seed oil extraction, the value of the internal mass transport coefficient of a single layer of oil-bearing cell has been calculated: its value is roughly the same for all the experimental cases analyzed (average value: 5 x 10(-8) m/s), verifying the reliability of the proposed model. (C) 2008 Elsevier B.V. All rights reserved