Study on the effect of simple, ready-to-apply solvent extraction methodologies on the physical, chemical and antioxidant properties of oil from spent coffee grounds

This study investigated oil recovery from spent coffee grounds (SCG) using mechanical high-speed-stirring (MHE) and accelerated solvent extraction (ASE), based on isooctane as oil recovering solvent. The impact of varying extraction times for MHE (5, 10, 15 min) and ASE (6, 12 min) on SCG oil yield, fatty acid profile, thermal behaviour, UV–Vis spectrum, caffeine and diterpenes (i.e., kahweol and cafestol) contents, antioxidant properties, and oxidative status was assessed, and compared to the results obtained using hexane-based Soxhlet. Application of MHE (∼10 %) and ASE (∼15 %) resulted in lower (−23 %) and higher (+12 %) extraction yields as compared to Soxhlet (∼13 %), respectively. No difference was observed in terms of fatty acid profile and thermal behaviour. Conversely, the application of MHE and ASE yielded significantly higher kahweol (+32 %) and cafestol (+12 %) contents, likely due to low MHE processing temperature and enhanced diterpenes decompartmentalization under pressurized ASE conditions. MHE and ASE were also able to yield a remarkably higher antioxidant activity (∼8-fold and ∼11-fold, respectively) and lower peroxide value (−69 % and −26 %, respectively) than Soxhlet, with MHE showing the lowest peroxide value. Results indicate the possibility to upcycle SCG into bioactive-rich oil using techniques with low investment burden, moderate processing costs, and high readiness levels, showing potential for application in diverse industrial sectors including food, cosmetics, and pharmaceuticals.