In this work, three extraction methods: Soxhlet, microwave irradiation and ultrasonic irradiation for extraction of lipids from spent coffee grounds were carried out using n‐hexane and petroleum benzene as solvent. Also, supercritical fluid extraction (SFE) using CO2 under different conditions was used for comparison. Different methods of extraction with organic solvents showed significant differences in the extraction yields. However, no significant differences were found when a given method (e.g., microwave irradiation) was applied using different organic solvents. On the other hand, different extraction conditions from the various runs of SFE resulted in significantly different extraction yields, all of which were higher than those of the other extraction methods using organic solvents except the Soxhlet extraction. No significant differences were observed in the fatty acid compositions of the extracted oils using organic solvents. However, the fatty acid compositions of the oils extracted under different conditions of SFE indicated significant differences among several fatty acids.
PRACTICAL APPLICATIONS
Supercritical fluid extraction (SFE) can be applied as a green technology to the oil extraction of spent coffee grounds (SCGs), as a waste product of the coffee industry, demonstrated in this work. Extraction using supercritical carbon dioxide is a feasible food processing unit operation, and no regulatory hurdles. The extraction yield of oil from SCGs was obtained at 98.14% relative to the Soxhlet extraction. This trend demonstrates that SFE can be a potential candidate for oil production from the waste product of the coffee industry.