Comparison of solvent systems on extraction, quality characteristics, and volatile compounds of palm kernel oil

Hexane (HEX) and dichloromethane (DCM) have been used to extract oils from various sources due to their expansive solubility and low volatility that ease removal at low temperatures. However, environmental and health concerns make them undesirable solvents. The aim of this study was to evaluate the extraction efficiency and physicochemical characteristics of palm kernel oil (PKO) extracted with the addition of acetone in HEX-acetone (1:1, vol/vol) and DCM-acetone (1:1, vol/vol) mixtures as an alternative to DCM and HEX alone. PKO extracted with co-solvent systems had better quality characteristics compared with single solvent extracts. The oil recovered, free fatty acid content, peroxide value and other quality characteristics, and thermal properties were within the range for PKO, and similar oils as stipulated in standards. Monounsaturated fatty acid content in PKO was up to 70% of which lauric acid was the most abundant (48%-52%). A total of 50 volatile compounds were identified by GC-MS in all the extracts including amide (1), alcohol (1), aldehydes (2), ketones (3), acids (6), esters (6) and hydrocarbons (31) with higher numbers of volatiles in the HEX extracts compared to the DCM extracts. Dodecanoic acid, hexanal, and 2-undecanone were the most abundant acid, aldehyde, and ketone, respectively. Principal component analysis (PCA) differentiated the volatiles identified on the polar and non-polar columns with 88.2% and 8.8%, and 67.3% and 19.6% of the variation accounted for by PC1 and PC2, respectively, with several common volatile components forming a cluster from all the solvents used.