Effect of moisture content on the extraction rate of coffee oil from spent coffee grounds using Norflurane as solvent

Recently, vegetable oils have been widely used in several industrial fields as food additives, biofuels, cosmetic ingredients, packaging materials, or pharmaceutical compounds. In this study, we investigated the extraction of lipids from spent coffee grounds using an innovative system and the hydrofluorocarbon Norflurane, as solvent. Extraction experiments were performed on matrices at different levels of moisture under a recirculating solvent flow in the pressure range 5-11 bar. The results confirmed the effectiveness of the novel extraction process on wet, dried and partially dried matrices, and the oil yields and the extraction times (approximately 92% in 75, 90 and 285 min respectively) were comparable with those obtained using the more expensive supercritical CO2 process. A kinetic approach was used to model the extraction rates of wet, dry and partially dried samples. It showed that a partial drying of the SCG promoted the solubilization of oil in Norflurane during the first extraction stage and improved the contact between Norflurane and the oily solute. The fatty acid profiles of the extracts were determined and the results revealed the presence of palmitic (C 16:0) and linoleic (C 18:2) acids, as major components, and stearic (C 18:0) and oleic (C 18:1) acids, as minor components. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.