Optimisation of supercritical carbon dioxide extraction of amaranth seeds by response surface methodology and characterization of extracts isolated from different plant cultivars

Isolation of amaranth seed lipids by supercritical carbon dioxide extraction (SCE-CO2) in order to obtain the highest oil yield was optimized using central composite design (CCD) and response surface methodology (RSM). The predicted optimal extraction process parameters yielding 15.5% of extract were 40 °C temperature, 35.8 MPa pressure, 110 min extraction time and 2.9 SL/min CO2 flow rate. The solubility of amaranth seed oil increased with temperature at high pressures, however it decreased with increasing temperature at lower pressures. CO2 flow rate was more important for the extraction speed than for the oil yield. The predicted models were highly significant (p < 0.05). SCE-CO2 and the predicted values of extraction method well fitted the experimental values. The composition of fatty acids and the content of squalene were analysed by chromatographic methods. The main fatty acids were linoleic, oleic and palmitic. Squalene content in the SCE-CO2 extract at optimal parameters was 12%. Twelve amaranth accessions were extracted at optimal conditions and the total oil yield varied from 10.6 to 16.7%, whereas the percentage of squalene in the extracts was in the range of 4.6–12.3%.