Phenomenological modeling and intensification of texturing/grinding-assisted solvent oil extraction: case of date seeds (Phoenix dactylifera L.)

Abstract

Accelerated Solvent Extraction (ASE) and Dynamic Maceration (DM) were used with n-hexane to study the extraction of oil from date seed powders with different particle sizes. The intensification was studied with instant controlled pressure drop (DIC) as texturing pretreatment. DM yields increased from 4.57% to 10.49 ± 0.05% dry–dry basis (ddb) when particle size decreased from 1.4 to 0.2 mm. For coarsely grounded seed powder, ASE oil yields were 11.35 ± 0.05% ddb and 14.15% ddb for untreated and DIC date-seeds, respectively. Optimized DIC pretreatment allowed the smallest particle size powder to get 15.2 ± 0.05% ddb as ASE yields, while the 2-h DM yields increased from 4.67 to 11.62 ± 0.05% ddb for particle size decreased from 1.4 to 0.2 mm, respectively. Fundamental analysis of various powders was achieved through washing–diffusion phenomenological model. DIC texturing implied higher washing stage, with relative starting accessibility %δYs of 70% against 55% for untreated particles. Consequently, the diffusion stage time was dramatically reduced, without great modification of effective diffusivity Deff value. Therefore, DIC ground seeds greatly enhanced the mass transfer mechanism. The evaluation of starting accessibility δYs enables to establish an empirical relationship between δYs and particle diameter δYs = f(D). Finally, DIC texturing did not imply any modification of the lipid profile. Keywords: Date seed oil, Solvent extraction kinetics, DIC, Particle size, Process intensification