Response Surface Analysis and Modeling of Flaxseed Oil Yield in Supercritical Carbon Dioxide

Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of particle size, pressure, temperature and the flow rate of supercritical carbon dioxide (SC-CO₂) were investigated. Response surface methodology was used to determine the effects of pressure (30–50 MPa), temperature (50–70 °C) and SC-CO₂ flow rate (2–4 g/min) on flaxseed oil yield in SC-CO₂. The oil yield was represented by a second order response surface equation (R ² = 0.993) using the Box-Behnken design of experiments. The oil yield increased significantly with increasing pressure (p < 0.01), temperature (p < 0.05) and SC-CO₂ flow rate (p < 0.01). The maximum oil yield from the response surface equation was predicted as 0.267 g/g flaxseed for 15 min extraction of 5 g flaxseed particles (particle diameter <0.850 mm) at 50 MPa pressure and 70 °C temperature, with 4 g/min solvent flow rate. Total extraction time at these conditions was predicted as 22 min.     

Time Fractionation of Minor Lipids from Cold-Pressed Rapeseed Cake Using Supercritical CO<Subscript>2</Subscript>

This work explored the possibility of using supercritical carbon dioxide (SC-CO₂) to achieve fractionation of pre-pressed rapeseed (Brassica napus) cake oil at 30–50 MPa, at 40 or 80 °C, and increase the concentration of minor lipids (sterols, tocopherols, carotenoids) in the oil. Minor lipids are partially responsible for desirable antioxidant effects that protect against degradation and impart functional value to the oil. The weight and concentration of minor lipids in oil fractions collected during the first 60 min were analyzed. Cumulative oil yield increased with pressure, and with temperature at ≥40 MPa, but was lower at 80 °C than at 40 °C when working at pressure ≤35 MPa. Differences in solubility between the oil and minor lipids explained fractionation effects that were small for tocopherols. Unlike tocopherols, which are more soluble in SC-CO₂ than the oil, sterols and carotenoids are less soluble than the oil, and their concentration increased in the later stages of extraction, particularly at ≥40 MPa, when there was not enough oil to saturate the CO₂ phase. Because of the fractionating effects on rapeseed oil composition, there was an increase in the antioxidant activity of the oil in the second half as compared to the first half of the extraction. Consequently, this study suggests that SC-CO₂ extraction could be used to isolate vegetable oil fractions with increased functional value.     

Optimization of Supercritical Carbon Dioxide Extraction of Gardenia Fruit Oil and the Analysis of Functional Components

Supercritical carbon dioxide (SC-CO₂) extraction of whole fruit oil from Gardenia jasminoides Ellis was performed. The effect of extraction pressure, temperature and CO₂ flow rate on the oil yield was investigated by response surface methodology (RSM). The results showed that experimental data had a good fit to the proposed model (R ² = 0.938). Extraction pressure, CO₂ flow rate, the quadratics of pressure, and the interaction between pressure and flow rate showed significant effects on the oil yield (p < 0.05). The optimum parameters that maximized the yield of gardenia fruit oil (GFO) were: extraction pressure of 36.8 MPa, temperature of 65 °C, and CO₂ flow rate of 15 kg/h. The main fatty acid of GFO was linoleic acid (about 44%), followed by palmitic acid (about 26.4%) and oleic acid (about 24.6%). α-Tocopherol was dominant in the total tocopherols of GFO, and showed the main antioxidant activity. The fatty acid composition and tocopherols content of GFO were not remarkably affected by the extraction by SC-CO₂ and n-hexane.     

Supercritical fluid extraction of daphne (Laurus nobilis L.) seed oil

Laurus nobilis L., commonly known as daphne tree, is an evergreen that belongs to the Lauraceae family. Daphne trees produce grape-sized shiny purplish berries having three parts: flesh, skin, and an inner kernel (single seed). This study examines supercritical CO₂ (SC-CO₂) extraction of oil from daphne seeds. The oil yield of ground seeds varied from 14 to 28% depending on the method and particle size used for oil recovery. Yields were similar for both petroleum ether and SC-CO₂ extraction. The extraction yield decreased significantly with increasing particle size. The amount of extract collected increased exponentially with increasing SC-CO₂ pressure. The highest extraction yield was obtained at the highest temperature studied, 75°C. More than 45% of the oil was lauric acid. SC-CO₂ is a viable technique to obtain high-purity L. nobilis L. seed oil, which is a potential ingredient for the cosmetic industry.     

Supercritical Carbon Dioxide Extraction and Characterization of Argentinean Chia Seed Oil

Extraction of chia seed oil was performed with supercritical carbon dioxide (SC-CO₂). To investigate the effects of pressure and temperature on the oil solubility and yield, two isobaric (250 and 450 bar) and two isothermal (40 and 60 °C) extraction conditions were selected. The global extraction yield of chia oil increased with pressure enhancement, but temperature had a little influence on it. The maximum oil recovery using SC-CO₂ at a mass flow rate of 8 kg/h was 97%, which was obtained at 60 °C, 450 bar for a 138-min extraction. The results showed that solubility changed from 4.8 g oil/kg CO₂ at 60 °C–250 bar to 28.8 g oil/kg CO₂ at 60 °C–450 bar. The final extract obtained by SC-CO₂ under different conditions and Soxhlet extraction contained mainly α-linolenic (64.9–65.6%) and linoleic (19.8–20.3%) acids. SC-CO₂ extraction is an interesting alternative methodology because it is possible to achieve a chia oil yield close to that obtained by conventional extraction with a similar fatty acid composition using an environmentally friendly process.     

Characterization of oil including astaxanthin extracted from krill (Euphausia superba) using supercritical carbon dioxide and organic solvent as comparative method

Krill oil including astaxanthin was extracted using supercritical CO₂ and hexane. The effects of different parameters such as pressure (15 to 25MPa), temperature (35 to 45 °C), and extraction time, were investigated. The flow rate of CO₂ (22 gmin⁻¹) was constant for the entire extraction period of 2.5 h. The maximum oil yield was found at higher extraction temperature and pressure. The oil obtained by SC-CO₂ extraction contained a high percentage of polyunsaturated fatty acids, especially EPA and DHA. The acidity and peroxide value of krill oil obtained by SC-CO₂ extraction were lower than that of the oil obtained by hexane. The SC-CO₂ extracted oil showed more stability than the oil obtained by hexane extraction. The amount of astaxanthin in krill oil was determined by HPLC and compared at different extraction conditions. The maximum yield of astaxanthin was found in krill oil extracted at 25 MPa and 45 °C.     

Supercritical CO2 extraction of flaxseed

Extraction of flaxseed oil was performed with supercritical carbon dioxide (SC-CO₂). To investigate the effects of pressure and temperature on the solubility of oil and oil yield, three isobaric (21, 35, and 55 MPa) and two isothermal (50 and 70°C) extraction conditions were selected. Although the maximal solubility of flaxseed oil, 11.3 mg oil/g CO₂, was obtained at 70°C/55 MPa, the oil yield obtained after 3 h of extraction at this condition was only 25% (g oil/g seed×100), which represented 66% of the total available oil of the flaxseed. Lipid composition and FFA and tocol (tocopherol and tocotrienol) contents of the oils obtained by both SC-CO₂ and petroleum ether extraction were determined. The α-linolenic acid content of the SC-CO₂-extracted oil was higher than that obtained by solvent extraction.     

Response surface optimization of Smyrnium cordifolium Boiss (SCB) oil extraction via supercritical carbon dioxide

In this study, the essential oil of aerial parts of a species of a plant called Smyrnium cordifolium Boiss (SCB) was extracted by supercritical CO₂. The essence was analyzed by the method of GC/MS. Design of experiments was carried out with response surface methodology by Minitab 16 software to optimize four operating variables of supercritical carbon dioxide (SC-CO₂) extraction (pressure, temperature, CO₂ flow rate and extraction dynamic time). This is the first report announcing optimization of the operation of supercritical extraction of SCB in laboratorial conditions. Optimizing process was done to achieve maximum yield extraction. Independent variables were dynamic time (t_d), pressure (P), temperature (T) and flow rate of SC-CO₂ (Q) in the range of 30–150 min, 10–30 MPa, 40–60 °C and 0.5–1.7 ml/min, respectively. The experimental optimal recovery of essential oil (0.8431, w/w%) was obtained at 13.43 MPa, 40 °C, 150 min (dynamic) and 1.7 ml/min (CO₂ flow rate).     

Characterization of wheat bran oil obtained by supercritical carbon dioxide and hexane extraction

Supercritical carbon dioxide (SC-CO₂) and soxhlet extraction using was carried out to extract oil from wheat bran oil. For SC-CO₂, the pressure and temperature were ranging from 10 to 30 MPa and 313.15–333.15 K. The extraction was performed in a semi batch process with a CO₂ flow rate of 26.81 g/min for 2 h. Wheat bran oil was characterized to investigate the quality. Acid value (AV) and peroxide value (POV) were higher in hexane extracted oil compared to SC-CO₂ extracted oil. Induction period was measured by rancimat test. The oil obtained by SC-CO₂ extraction had higher capability to delay the oxidation by surrounding environment. The DPPH radical scavenging activity was also measured. The SC-CO₂ extracted oil showed higher radical scavenging activity compared to hexane extracted oil.     

Effect of moisture and particle size on the extractability of oils from seeds with supercritical CO2

Moisture level and particle size of soybeans, peanuts and cottonseed were correlated with the extraction rate and yield of oil when extracted with supercritical carbon dioxide (SC-CO₂) at a constant temperature (50 C) and pressure (8000 psig). The rate of extraction and ultimate oil yields were quite low with cracked soybeans. However, good extraction rates and nearly theoretical oil yields were obtained from ground or thinly flaked (<0.010″) seeds. Moisture levels between 3% and 12% had little effect on extracability. Oil composition was not influenced by either parameter. Scanning electron microscopy was used to study seed structure before and after extraction with SC-CO₂. Micrographs of SC-CO₂-extracted seeds were similar to hexane-extracted seeds. Presented at the AOCS Meeting, May 1983, Chicago.     

Supercritical Carbon Dioxide Extraction of <Emphasis Type="Italic">Microula sikkimensis</Emphasis> Seed Oil

The seed oil of Microula sikkimensis had been intensively studied due to its pharmacological actions. In the present study, seed oil of Microula sikkimensis was extracted using supercritical fluid extraction (SFE). Determinations of the extracts composition were performed by gas chromatography (GC). An orthogonal array design (OAD), OA₉ (3⁴), was employed for optimization of the supercritical fluid extraction of the compound with regard to the various parameters. Four factors, namely pressure (21.0–27.0 MPa), the dynamic extraction time, temperature, and CO₂ flow rate of the supercritical fluid, were studied and optimized by a three-level OAD. The effects of the parameters on the yield of seed oil were studied using analysis of variance (ANOVA). The results revealed that the pressure had a significant effect on the yield of seed oil (p < 0.05), while the other three factors, i.e., CO₂ flow rate, dynamic extraction time and temperature, were not identified as significant factors under the selected conditions based on ANOVA. The results show that the best values for the extraction condition of seed oil was pressure 24.0 MPa, extraction time 3 h, temperature 45 °C and a CO₂ flow rate 20 L/h in the 20-L vessel.     

Supercritical Carbon Dioxide Extraction of Sorghum Bug (<Emphasis Type="Italic">Agonoscelis pubescens</Emphasis>) Oil Using Response Surface Methodology

Supercritical fluid extraction (SFE) of sorghum bug oil (SBO) with carbon dioxide was performed and compared with Soxhlet extraction using hexane. Response surface methodology (RSM) was used to determine the effects of pressure (200–400 bar) and temperature (50–70 °C) on the sorghum bug oil yield in SC-CO₂. The high extraction yield (more than 45.0%) was obtained at 300 bar and 60 °C followed by 400 bar and 70 °C, while the lower yield was obtained at 159 bar and 60 °C. At low pressure levels (159 and 200 bar), the oil yield decreased due to the reduced density of CO₂ at higher temperatures. Gas chromatography was used to characterize the fatty acids of the oils obtained while α-tocopherol was quantified by HPLC. No differences were found in the fatty acid compositions of the various extracts, while the α-tocopherol extracted from sorghum bug oil by the conventional solvent method was less than that extracted by the SFE process using CO_2. It can be observed that the conventional solvent extraction method exhibited notable DPPH radical-scavenging activity, with an efficacy slightly lower (IC₅₀ 7.45 ± 0.3) than that of the SFE extracts.     

Antioxidant Activity and Total Polyphenols Content of Camellia Oil Extracted by Optimized Supercritical Carbon Dioxide

In this study, Camellia oil is co-extracted from Camellia oleifera seeds and green tea scraps by supercritical carbon dioxide (SC-CO₂), which is optimized on the extraction yield, ABTS-scavenging activity, and total polyphenols content (TPC) of oil by single-factor experiments combined with response surface methodology (RSM). The extraction temperature, pressure, dynamic time, carbon dioxide (CO₂) flow rate, and seed mass ratio were investigated with single-factor experiments. The results indicated the optimum CO₂ flow rate and dynamic extraction time were 15 L hour⁻¹ and 60 min (i.e., 2.382 kg CO₂/100 g sample). Furthermore, the complicated effects of extraction temperature (40–50 °C), pressure (20–30 MPa), and seed mass ratio (0.25–0.75) were optimized by RSM based on the Box–Behnken design (BBD). The models with high R-squared values were obtained and used to predict the optimum operating conditions of the process. Under the optimum operating conditions (i.e., temperature of 46 °C, pressure of 30 MPa, and seed mass ratio of 0.35), the extraction yield, ABTS-scavenging activity, and TPC of oil were 14.43 ± 0.17 g/100 g sample, 73.70 ± 0.34%, and 2.18 ± 0.05 mg GAE/g oil, which were in good agreement with the predicted values. In addition, the experiments indicated that the Camellia oil obtained was rich in polyphenols, resulting in better oxidation stability and antioxidant activity than the original oil.     

Ethanol modified supercritical carbon dioxide extraction of flavonoids from Momordica charantia L. and its antioxidant activity

Ethanol modified supercritical carbon dioxide (SC-CO₂) extraction of flavonoids from Momordica charantia L. fruits and its antioxidant activity were performed. The influences of parameters such as temperature, extraction time and pressure on the yield of flavonoids were investigated. The antioxidant activities of flavonoids were assessed by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and β-carotene bleaching test. The experimental data obtained indicated that pressure, temperature and time had significant effect on the extraction yield. The optimum extraction conditions, determined by the 3D response surface and contour plots derived from the mathematical models, were as follows: extraction temperature 46 °C, pressure 33.4 MPa, and extraction time 53.2 min. Under these conditions, the experimental value was 15.47 mg/g, which was well matched with value predicted by the model. The antioxidant activity of flavonoids obtained by ethanol modified SC-CO₂ extraction method had higher antioxidant activity than the flavonoids extracted by conventional solvent extraction (CSE) method. The DPPH radical-scavenging ability of flavonoids obtained by ethanol modified SC-CO₂ extraction method reached to 96.14 ± 1.02%, equivalent to the clearance rate of ascorbic acid at 1.2 mg/mL. Results indicated that ethanol modified SC-CO₂ extraction was a suitable approach for the selective extraction of flavonoids from M. charantia L.     

Effects of supercritical CO2 extraction parameters on chemical composition and free radical-scavenging activity of pomegranate (Punica granatum L.) seed oil

Pomegranate (Punica granatum L.) seed oil (PSO) was prepared by supercritical CO₂ (SC-CO₂) extraction technology. Changes in the yield, chemical composition and free radical-scavenging activity of PSO under different extraction parameters were investigated. The results of SC-CO₂ extraction revealed that extraction pressure was the dominant factor to affect the oil yield. PSO was characterized by a high content of punicic acid (approximately 60%) and γ-tocopherol (more than 300 mg/100 g oil). A slight increase in the contents of punicic acid, arachidic acid and gadoleic acid was observed under higher extraction pressure and temperature. At lower pressure or shorter extraction time, PSO with high amount of total tocopherols was obtained. PSO extracted by SC-CO₂ showed strong free radical-scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenz-thiazoline-6-sulfonic) diammonium salt (ABTS) radicals and its scavenging ability was correlated with the level of tocopherols in extracted oils.     

Supercritical carbon dioxide extraction,purification, and characterization of wax from sorghum and sorghum by-products as an alternative natural wax

The objective of this work was to obtain high purity natural wax from sorghum and by-products of sorghum processing (sorghum dried distillers grains with solubles [DDGS] and sorghum bran) using a green process based on supercritical carbon dioxide (SC-CO₂). SC-CO₂ extractions were carried out at varying temperatures (50, 70°C) and pressures (30, 40 MPa) at a CO₂ flow rate 1 L/min for 120 min. Significantly higher wax yield (4.9%) from DDGS was obtained by SC-CO₂ at 40 MPa/70°C compared with whole kernel (0.6%) and bran (3.3%) (p < 0.05). The yield of the extracts obtained by SC-CO₂ extraction was higher than that of the conventional hexane extraction for all three sorghum sources. The highest fraction of wax in the SC-CO₂ extracts was obtained from whole kernel extracts (89%), whereas it was 53.3% from the DDGS and 26.8% from the bran at the same extraction conditions. SC-CO₂ and hexane extracts from sorghum whole kernel shared a similar melting peak temperature of 76.3–77.9 and 79.7°C, respectively, while DDGS and bran extracts by SC-CO₂ showed a much lower melting temperature in the range of 50.7–61.9°C, indicating the presence of lower melting point components such as triacylglycerols. However, the melting points of the DDGS and bran extracts after ethanol purification were significantly increased with the observed peak temperature of 80.8 and 82.0°C, respectively. While the wax yield from DDGS and bran was higher than that of whole kernel, the sorghum whole kernel feedstock was found to be a more feasible feedstock to obtain higher purity wax.     

Supercritical carbon dioxide extraction of oil from Thunnus tonggol head by optimization of process parameters using response surface methodology

Total oil was extracted from ground fish head of Longtail tuna (Thunnus tonggol) using supercritical carbon dioxide (SC-CO₂) at 20 to 40 MPa, 45 to 65 °C and 1 to 3 ml min^?1. Response surface methodology (RSM) was employed to optimize the operating conditions of the SC-CO₂ technique where the highest oil yield was obtained (35.6% on dry weight basis) at 40 MPa, 65 °C, and 3 ml min^?1. The solubility of the oil in SC-CO₂ increased from 2.9 to 14.2 g oil/100 g of CO₂ with increasing pressure and temperature. The total saturated, monounsaturated and polyunsaturated fatty acids obtained were 41.6, 24.7 and 26.8%, respectively, where the omega-3 fatty acids were found to be 22.3%. A correlation was developed determining the coefficients of the second-order polynomial equation where the extraction parameters of SC-CO₂ method to extract fish oil from fish sample were successfully optimized using response surface methodology.     

Supercritical CO2 extraction of rice bran

Extraction of rice bran lipids with supercritical carbon dioxide (SC-CO₂) was performed. To investigate the pressure effect on extraction yield, two isobaric conditions, 7000 and 9000 psi, were selected. A Soxhlet extraction with hexane (modified AOCS method Aa 4–38; 4 h at 69°C) was also conducted and used as the comparison basis. Rice bran with a moisture content of 6%, 90% passable through a sieve with 0.297 mm opening, was used for extraction. A maximum rice bran oil (RBO) yield of 20.5%, which represents 99+% lipid recovery, was obtained with hexane. RBO yield with SC-CO₂ ranged between 19.2 and 20.4%. RBO yield increased with temperature at isobaric conditions. At the 80°C isotherm, an increase in RBO yield was obtained with an increase in pressure. The pressure effect may be attributed to the increase in SC-CO₂ density, which is closely related to the value of the Hildebrand solubility parameter. RBO extracted with SC-CO₂ had a far superior color quality when compared with hexane-extracted RBO. The level of sterols in SC-CO₂-extracted RBO increased with pressure and temperature.     

Compositional and Antioxidant Activity Analysis of <Emphasis Type="Italic">Zanthoxylum bungeanum</Emphasis> Seed Oil Obtained by Supercritical CO<Subscript>2</Subscript> Fluid Extraction

Supercritical CO₂ fluid extraction (SFE-CO₂) of Zanthoxylum bungeanum (Z. bungeanum) seed oil was investigated. To optimize the SFE process, three-level Box-Behnken factorial design and response surface methodology (RSM) were applied to optimize the extraction conditions, including pressure, temperature and amount of modifier. The optimum conditions were as follows: extraction pressure, 29.28 MPa; extraction temperature, 41.19 °C; and the added amount of modifier, 10.94%. The experimental results showed that the maximum extraction yield was 21.85 ± 0.23% (n = 3) under the proposed conditions. The compositional analysis of Z. bungeanum seed oil was performed by HPLC-FLD-MS using a new labeling reagent of 2-(11H-benzo[a]carbazol-11-yl)-ethyl-4-methyl benzenesulfonate (BCETS). The results indicated that the Z. bungeanum seed oil contained mainly unsaturated fatty acids, including C18:3, C22:6, C20:4, C18:2, C18:1 and C20:1, which accounted for 84.0% (mass percentage) of the total amount. The antioxidant activity of seed oil obtained by Box-Behnken design concerning the DPPH radical was investigated, and this indicated that the pressure and the amount of added modifier had positive effects on the antioxidant activity, but the effect of the temperature elevation is complicated, depending on the nature of the extracted contents.     

Supercritical carbon dioxide extraction of microalgae lipid: Process optimization and laboratory scale-up

Supercritical carbon dioxide (SC-CO₂) extraction of lipid from Scenedesmus sp. for biodiesel production was investigated and compared to conventional extraction methods. The effect of biomass pre-treatment prior to extraction and extracting conditions, namely pressure in the range of 200–500 bar, temperatures in the range of 35–65 °C and CO₂ flow rate in the range of 1.38–4.02 g min⁻¹, on SC-CO₂ extraction yield and quality of lipid were investigated. Three levels full factorial design of experiments and response surface methodology was used to model the system. A second order polynomial model was developed and used to predict the optimum conditions. Scaling up to a laboratory larger scale was also tested. The results indicated that SC-CO₂ extraction was superior to other extraction techniques, but exhibited significant variations in yield with changes in operating parameters. In the developed model, it was found that the linear and quadratic terms of the temperature, as well as the interaction with pressure had a significant effect on lipid yield; whereas, their effect on lipid quality was insignificant. The best operating conditions, in the tested range, were 53 °C, 500 bar and 1.9 g min⁻¹, in which lipid extraction yield of 7.41% (dry weight basis) was obtained. Negligible differences were observed when the fatty acid composition of SC-CO₂ extracted lipid was compared to that extracted by the conventional methods. At the optimum conditions, SC-CO₂ extraction was successfully scaled-up by eight-folds and the extracted lipid yield dropped by 16%.