Response Surface Optimization of Nigella glandulifera Freyn Seed Oil Yield by Supercritical Carbon Dioxide Extraction 155 y (oil yield,% 1.00 382 37.025 0.50 ●373729 35.85 i 34.675 0.00 36677 33.5 -0.50 3307内 07④ 1.00 1.00 ●5866 0.50 0.50 0.00 0.00 34☒ -0.50 -1.00 (flow rate.Lh) 0.50 -1.00-1.00 -1.00 -0.50 0.00 0.50 1.00 X(temperature,C) (temperature,C) Fig.3 Response surface curve and its contour plot for the effects of temperature and CO,flow rate at a constant extraction pressure of 30 MPa on the oil yield. and the result is shown in Fig.4.The plot demon- 37.9 strates that the experimental points are evenly distrib- 37.7 uted around the diagonal of horizontal and vertical axis, which indicates that the experimental values are in good 37.5 1-0.9852r+0.573 agreement with the predicted values,and also suggests d that the predicted second order polynomial model is 37.3 accurate and reliable.Thus,a statistically significant 37.1 multiple regression relationship between the indepen- 37 373 37.5 37.7 37.9 dent variables (pressure,temperature,and CO,flow Observed value (% rate)and the response variable(oil yield)was established. The second order polynomial model could therefore be Fig.4 Observed values vs.predicted values for model verification. effectively used to represent the relationship among the parameters selected. consistent with the effect of N.glandulifera seed in activating blood circulation.The essential fatty acids Fatty acid composition of N.glandulifera seed oil like linoleic acid are not easily synthesized in the human body and must be supplied externally through the The fatty acid composition of N.glandulifera seed oil diet,and N.glandulifera seed oil can be a good nutri- extracted by SC-CO,and by Soxhlet method was de- tional supplement as a source of linoleic acid. termined by gas chromatography-mass spectrometry (GC-MS)and is shown in Table 3.The result shows that the fatty acid composition of oil extracted by the CONCLUSION two methods is similar,and the content of linoleic acid and oleic acid reached up to 48.30 and 22.28%, RSM was successfully applied for optimization of SC- respectively.As can be observed,the composition and CO,extraction parameters for N.glandulifera seed oil content in fatty acids do not depend on the extraction yield.The response surface plots indicated that the method.The oil contained 12 fatty acids,among them, three factors(pressure,temperature and CO,flow rate) linoleic acid was the most abundant unsaturated fatty significantly influenced the oil yield,independently and acids.This work also shows that N.glandulifera Freyn interactively.The optimum process parameters were seed oil is a rich source of linoleic acid.Linoleic acid obtained as:pressure 30.84 MPa,temperature 40.57C, has the ability to inhibit platelet aggregation,which is and CO,flow rate 22 L h.Under these conditions,the 2012,CAAS.All rights reserved.Published by Elsevier Ltd.Response Surface Optimization of Nigella glandulifera Freyn Seed Oil Yield by Supercritical Carbon Dioxide Extraction 155 © 2012, CAAS. All rights reserved. Published by Elsevier Ltd. consistent with the effect of N. glandulifera seed in activating blood circulation. The essential fatty acids like linoleic acid are not easily synthesized in the human body and must be supplied externally through the diet, and N. glandulifera seed oil can be a good nutri￾tional supplement as a source of linoleic acid. CONCLUSION RSM was successfully applied for optimization of SC￾CO2 extraction parameters for N. glandulifera seed oil yield. The response surface plots indicated that the three factors (pressure, temperature and CO2 flow rate) significantly influenced the oil yield, independently and interactively. The optimum process parameters were obtained as: pressure 30.84 MPa, temperature 40.57°C, and CO2 flow rate 22 L h-1. Under these conditions, the Fig. 4 Observed values vs. predicted values for model verification. and the result is shown in Fig. 4. The plot demon￾strates that the experimental points are evenly distrib￾uted around the diagonal of horizontal and vertical axis, which indicates that the experimental values are in good agreement with the predicted values, and also suggests that the predicted second order polynomial model is accurate and reliable. Thus, a statistically significant multiple regression relationship between the indepen￾dent variables (pressure, temperature, and CO2 flow rate) and the response variable (oil yield) was established. The second order polynomial model could therefore be effectively used to represent the relationship among the parameters selected. Fatty acid composition of N. glandulifera seed oil The fatty acid composition of N. glandulifera seed oil extracted by SC-CO2 and by Soxhlet method was de￾termined by gas chromatography-mass spectrometry (GC-MS) and is shown in Table 3. The result shows that the fatty acid composition of oil extracted by the two methods is similar, and the content of linoleic acid and oleic acid reached up to 48.30 and 22.28%, respectively. As can be observed, the composition and content in fatty acids do not depend on the extraction method. The oil contained 12 fatty acids, among them, linoleic acid was the most abundant unsaturated fatty acids. This work also shows that N. glandulifera Freyn seed oil is a rich source of linoleic acid. Linoleic acid has the ability to inhibit platelet aggregation, which is Fig. 3 Response surface curve and its contour plot for the effects of temperature and CO2 flow rate at a constant extraction pressure of 30 MPa on the oil yield