Supercritical CO₂ extraction of lipids from grain sorghum dried distillers grains with solubles

Experiments were carried out on a lab supercritical CO₂ extraction system to determine the effects of extraction conditions, including mass ratio of CO₂ consumed to distillers dry grain with solubles (DDGS) extracted, extraction pressure, extraction temperature and time, on yield and composition of extracted lipids. A maximum lipid yield of 150 g/kg DDGS was achieved with a mass ratio ∼45, an extraction pressure at 27.5 MPa, an extraction temperature at 70 °C and an extraction time of 4 h. Under these extraction conditions, the contents of tocols, phytosterols, policosanols and free fatty acids were 0.44, 15.6, 31.2 and 155.3 mg/g in the extract. Experimental results indicated that shorter extraction time and higher flow rate of CO₂ can achieve higher contents of tocols, phytosterols and policosanols but lower content of free fatty acids in the lipid extract. Extraction conditions had no observed effects on the composition of free fatty acids in the extract. Palmitic, oleic and linoleic acids were three main free fatty acids extracted and constituted about 94% of all free fatty acids.