Abstract
Spent coffee grounds (SCG) are a potentially sustainable source of C16-C18 triglycerides. This study investigates known solvent extraction technologies with a wide range of solvents for lipid extraction from SCGs, and determines the effect of solvent selection and process temperature on the extraction efficiency and composition of the obtained oil. A correlation between increasing solvent boiling point, and therefore process temperature, and improved oil extraction efficiency was observed in Soxhlet extractions with a wide range of solvents. Experiments at elevated temperatures (up to 200 °C) were performed through Accelerated Solvent Extraction (ASE) and temperature increase initially improved the oil extraction efficiency when non-polar solvents were used, before decreasing it at higher temperatures. Utilization of ethanol resulted in the highest oil extraction ratio by ASE (at 165 °C), suggesting that temperature increase is more beneficial to the extraction efficiency of polar solvents. In addition, analysis of the oils was carried out to evaluate the composition of the oils extracted from SCGs using different solvents and extraction parameters. The Nuclear Magnetic Resonance (NMR) results were in agreement with the values obtained from the titrimetric determination of the free fatty acid content (FFA) of the oils in terms of the comparative trends, and also tentatively suggest that some differences in the composition of the extracted oils might be related to the type of extraction solvent used.
Highlights
Coffee is a crop cultivated in 80 countries and one of the most popular beverages worldwide (Campos-Vega et al, 2015; Murthy and Madhava Naidu, 2012)
This paper presents results of experimental investigations into effect of solvent extraction conditions on oil extraction efficiency and composition of oils extracted from Spent coffee grounds (SCG), with a comprehensive range of polar and non-polar extraction solvents investigated along with varying process temperatures
A range of oils extracted from the SCGs were selected for analysis by 1H Nuclear Magnetic Resonance (NMR); these were the oils obtained from Soxhlet extraction, and oils extracted by Accelerated Solvent Extraction (ASE) using ethanol and n-hexane at various temperatures
Summary
Coffee is a crop cultivated in 80 countries and one of the most popular beverages worldwide (Campos-Vega et al, 2015; Murthy and Madhava Naidu, 2012). Previous studies that investigated the extraction of lipids from SCGs through the Soxhlet method reported oil yields ranging from 7 to 30.4% w/w on a dry weight basis, with most researchers reporting values between 11 and 20% w/w (Al-Hamamre et al, 2012; Caetano et al, 2012; Deligiannis et al, 2011; Efthymiopoulos et al, 2017; Haile, 2014; Jenkins et al, 2014; Pichai and Krit, 2015). The FFA content of the extracted SCG oil samples was determined by titration, with NMR analysis undertaken in order to make a preliminary assessment of changes in extracted oil composition when different solvents were used
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
