Chemical composition and antioxidant activity of oil obtained from coconut meal by subcritical ethanol extraction

This work aimed to evaluate the efficiency of subcritical ethanol extraction for recovering oil from coconut meal. Dried coconut meal with an oil content of 19.85% (w.b.) was treated with subcritical ethanol at various ethanol concentrations (80, 90, and 100% v/v), solvent to solid ratios (5:1, 8:1, 10:1, and 15:1 v/w), temperatures (80, 100, and 120 °C), and holding times (0, 15, 30, and 45 min) in a batch-type vessel. The highest oil recovery (81.49%), which was obtained from the extraction with 100% ethanol and solvent-solid ratio of 8:1 (v/w) at 100 °C for 45 min did not significantly differ from those obtained at 120 °C for 15–45 min. The chemical properties, including free fatty acid content, peroxide value, saponification value, unsaponifiable matter, and fatty acid profile of the oils conformed to the standard values for crude coconut oil. Gas chromatography showed the higher ratios of caprylic and capric acids in the subcritical ethanol-extracted oils than those in hexane extracted oil, approximately 1.05–1.4 times. Additionally, the total phenolic content and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity of the oils extracted with the subcritical ethanol extraction were significantly higher (up to 3.5 and 6 times, respectively) than those of the oil Soxhlet-extracted with hexane. The present study showed that subcritical ethanol extraction is an effective method for extracting oil with good qualities and antioxidant properties from coconut meal.