Recovery of spent coffee grounds oil using supercritical CO2: Extraction optimisation and physicochemical properties of oil

Abstract

Soxhlet and accelerated solvent extraction, using propanol as a solvent, and supercritical CO2 extraction methods presented statistically insignificant differences in the crude oil yield obtained from spent coffee grounds. Supercritical CO2 extraction method was selected to recover the oil. The optimal extraction condition for a high crude oil yield, low acid value, percentage of free fatty acids, peroxide value and thiobarbituric acid reactive substances (TBARS) value, and high iodine and saponification values, was obtained simultaneously at 50°C, 200 bar and 2 h. Under this condition, the experimental data obtained, namely 12.14% oil yield, acid value 3.89 mg KOH/g oil, 2.11% free fatty acids, iodine value 90.70 g I2/g oil, saponification value 212.05 mg KOH/g oil, peroxide value 3.77 mEqO2/kg oil and TBARS value 0.76 mg malondialdehyde/kg oil, were reasonably close to the predicted values. Additionally, the oil from spent coffee grounds is a precious source of palmitic and linoleic acids.

Keywords

• spent coffee grounds
• soxhlet
• accelerated solvent extraction
• supercritical co2 extraction
• response surface methodology