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: 5 × 10−8 m/s), verifying the reliability of the proposed model.

Graphical abstractIn this work, an extraction model capable of predicting the supercritical extraction process of seed oil is presented. The model takes into account the seed structure: the ground seed particles are considered being composed of concentric shells consisting of oil-bearing cells that progressively exhaust their oil content. The internal mass transport coefficient is described with three alternative models: a discrete, a continuous and a semi-continuous one.Figure optionsDownload full-size imageDownload as PowerPoint slideDimensionless overall mass-transfer coefficient versus the exhaustion degree of the particle for the three kinetic local models.