Supercritical Extraction Kinetics of Seed Oil: A New Model Bridging the 'Broken and Intact Cells' and the 'Shrinking Core' Models

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: 5x10-8 [m/s]), verifying the reliability of the proposed model.