Supercritical CO2 extraction of rosehip seed oil: Fatty acids composition and process optimization

Rosehip seed oil has been extracted using supercritical CO₂ at various operating conditions to optimize extraction process. The effect of extraction conditions on the fatty acids composition in the oil was also observed. The extraction conditions were as follows: pressures (P) of 150, 300 and 450 bar, temperatures (T) of 40, 60 and 80 ^oC, and CO₂ flow rate (F) of 2, 3 and 4 mL/min. A full 3³ factorial design coupled with statistical and graphical analysis of the results, by using analysis of variance (ANOVA) was applied to optimize variables in the process of rosehip seed oil extraction with SC-CO₂. The experimental result showed that the seed oil extracted mainly contained linoleic acid (C18:2) as the most abundant followed by linolenic (C18:3), palmitic (C16:0) and stearic acid (C18:0); and the extraction conditions influenced the fatty acids composition. The analysis of experimental design for process optimization results demonstrates that temperature and pressure were to be the influential variables on the extraction yield of seed oil. Furthermore, the apparent solubility of oil in SC-CO₂ was also determined from the experimental data and correlated using empirical equations for further model developing.     

Exploiting microalgae as a source of essential fatty acids by supercritical fluid extraction of lipids: Comparison between Scenedesmus obliquus,Chlorella protothecoides and Nannochloropsis salina

Supercritical CO₂ extraction from microalgae is applied with the aim of obtaining an oil rich in α-linolenic (ALA) essential fatty acid and with a low ω6:ω3 ratio. The maximum extraction yield is obtained at 60 °C and 30 MPa with 0.4 kg/h of CO₂ and 5% of co-solvent (ethanol). When the effect of pressure, temperature and density on the supercritical extraction yield and solubility are studied, the thermodynamic cross-over is found at a pressure close to 30 MPa, while the extraction cross-over occurs at around 25 MPa. The experimental solubility data are correlated by literature empirical models. Mathematical models developed by Sovová are applied to describe the experimental extraction curves. Soxhlet extraction of lipids is also carried out, obtaining a similar fatty acids profile but proving to be less selective than SCCO₂ method. Among the three species of microalgae examined, results show that Scenedesmus obliquus oil is richer in ω-3 fatty acids and ALA than Chlorella protothecoides and Nannochloropsis salina lipids. The effect of the extraction parameters on ALA content and the fatty acid profile is also analysed, concluding that the ω-3 percentage is favoured by lower temperatures, lower pressures and shorter extraction times.     

Determination and calculation for solubility of m-nitroaniline and its mixture in supercritical carbon dioxide

Equilibrium solubility of m-nitroaniline and p-nitroaniline in supercritical carbon dioxide (SCCO₂) is essential to design the process of SCCO₂ extraction and to investigate the effect of each solute on the solubility in SCCO₂ ternary system. However, the solubility data is not reported so far. We performed the solubility measurements at the temperatures of 308–328 K and in the pressure range of 11.0–21.0 MPa. The experimental results showed the solubility of m-nitroaniline and p-nitroaniline was enhanced in m-nitroaniline + p-nitroaniline + SCCO₂ ternary system. The improvement factor (i), separation factor (μ) and separation efficiency (HE) in the ternary system were defined and calculated, and the best separation result could be obtained at 21.0 MPa and 328 K using SCCO₂ extraction, where the separation efficiency was up to 90.9%. Based on the chemical association theory, a new model was developed to calculate the solubility of mixed solutes in SCCO₂. The correlation result of the new model was tested by about 500 solubility data from 15 kinds of two solutes mixtures in SCCO₂. The correlated result showed that the new model could achieve much better AARD (%) than those of frequently used Sovova and Sovova-T models.     

Solubility of niflumic acid and celecoxib in supercritical carbon dioxide

The solubility data of two fluorinated and non-steroidal anti-inflammatory drugs, niflumic acid (CAS No. 4394-00-7) and celecoxib (CAS No. 169590-42-5), in supercritical carbon dioxide were measured with a semi-flow type phase equilibrium apparatus at temperatures ranging from 313.2 K to 353.2 K and pressures up to 31 MPa. At the highest extraction temperature and pressure, the solubilities are 2.09 × 10⁻⁵ and 1.52 × 10⁻⁵ in mole fraction for niflumic acid and celecoxib, respectively. The saturated solubility data were correlated with the Chrastil model, the Mendez-Santiago–Teja equation, and the Peng–Robinson equation of state. The Chrastil model fitted the experimental data to about within the experimental uncertainty. The correlated results of the Mendez-Santiago–Teja model confirmed the consistency of the solubility data over the entire experimental conditions. Incorporating with two-parameter van der Waals one-fluid mixing rules, the Peng–Robinson equation of state represents satisfactorily the gas–solid equilibrium behavior of niflumic acid and celecoxib in supercritical carbon dioxide.     

Supercritical CO2 extraction of omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds

Supercritical carbon dioxide (SC-CO₂) was employed to extract omega-3 rich oil from Sacha inchi (Plukenetia volubilis L.) seeds and partially defatted cake. For ground seeds, the supercritical extraction was carried out at temperatures of 40, 50 and 60 °C and pressures of 300 and 400 bar, and for the cold pressed partially defatted cake, the extraction was carried out with 300 bar at 40 °C and with 400 bar at 60 °C. The global extraction yields (X₀), oil solubility, fatty acid composition of the oil and tocopherol content were determined. The seed samples used in this work contained 54.3% oil, of which 50.5% was linoleinc acid (ω-3). The maximum extraction recovery for the seeds as 92% at 400 bar and 60 °C, but on one occasion a recovery of 99.1% oil was obtained when cold pressed extraction was employed, followed by supercritical extraction at 400 bar and 60 °C. A high tocopherol content of about 2–3 g/kg of oil was obtained.     

Extraction of jojoba seed oil using supercritical CO2+ethanol mixture in green and high-tech separation process

In this study, the extraction of jojoba seed oil obtained from jojoba seed using both supercritical CO₂ and supercritical CO₂+ethanol mixtures was investigated. The recovery of jojoba seed oil was performed in a green and high-tech separation process. The extraction operating was carried out at operating pressures of 25, 35 and 45 MPa, operating temperatures of 343 and 363 K, supercritical fluid flow rates of 3.33 × 10⁻⁸, 6.67 × 10⁻⁸ and 13.33 × 10⁻⁸ m³ s⁻¹, entrainer concentrations of 2, 4 and 8 vol.%, and average particle diameters of 4.1 × 10⁻⁴, 6.1 × 10⁻⁴, 8.6 × 10⁻⁴ and 1.2 × 10⁻³ m. It was found that a green chemical modifier such as ethanol could enhance the solubilities, initial extraction rate and extraction yield of jojoba seed oil from the seed matrix as compared to supercritical CO₂. In addition, it was found that the solubility, the initial extraction rate and the extraction yield depended on operating pressure and operating temperature, entrainer concentration, average particle size and supercritical solvent flow rate. The solubility of jojoba seed oil and initial extraction rate increased with temperature at the operating pressures of 35 and 45 MPa and decreased with increasing temperature at the operating pressure of 25 MPa. Furthermore, supercritical fluid extraction involved short extraction time and minimal usage of small amounts entrainer to the CO₂. About 80% of the total jojoba seed oil was extracted during the constant rate period at the pressure of 35 and 45 MPa.     

Liquid and supercritical CO2 extraction of fat from rendered materials

The separation of fat from rendered materials has potential for value-added products, fuels and feed sources for animals. Current industrial processes utilize continuous screw pressing to extract fat from rendered materials, but the ability to minimize residual fat content is limited. In this work, liquid and supercritical CO₂ were used to extract the remaining fat from rendered poultry meal. CO₂ extraction offers high extraction yields with potential ecological and economic benefits for the rendering industry. A semi-batch extraction unit was used to investigate the effect of pressure (69–345 bar), temperature (25 °C, 40 °C and 50 °C), flow rate, and mass of CO₂ on the extraction yield and the fat solubility. Maximum extraction yields between 87% and 97% were obtained which produced a remaining fat content of 1.0 ± 0.3 wt% in the extracted poultry meal. Fat solubility increased with pressure but decreased with temperature, providing liquid CO₂ with the highest fat solubility (6.47 g/L) at 25 °C and 345 bar. The Chrastil model successfully correlated the solubility data as a function of density and temperature, obtaining an AARD value of 5.56%. Gas chromatography was used to analyze the composition of fatty acids, obtaining similar results with those reported in the literature. It can be concluded that high fat extraction yields can be obtained using CO₂ and that liquid CO₂ is more effective than supercritical CO₂ for the extraction of rendered fats under the conditions tested.     

Application of response surface methodology for the optimization of supercritical carbon dioxide extraction and ultrasound-assisted extraction of Capparis spinosa seed oil

Caper (Capparis spinosa) seed oil growing wild in Iran was extracted using supercritical CO₂ and ultrasound-assisted extraction methods. The experimental parameters of SFE and UAE were optimized using a rotatable central composite design. The highest yield for SFE was obtained at a pressure of 355 bar, temperature of 65 °C, modifier volume of 140 μL, static and dynamic extraction time of 10 and 35 min, respectively, and for UAE was gained at solvent volume of 23 mL, sonication time of 45 min and temperature of 40 °C. This resulted in a maximum oil recovery of 25.1% and 27.9% for SFE and UAE, respectively. The extracts with higher yield from both methods were subjected to transesterification and GC–MS analysis. SFE and UAE processes selectively extracted the fatty oils with high percentage of omega-6 and omega-9-fatty acids. The major components of the extracted oils from both methods were linoleic, oleic, its positional isomer cis-vaccenic and Palmitic acid.     

Optimization of supercritical fluid extraction of phytosterol from roselle seeds with a central composite design model

Recovery of phytosterol from roselle (Hibiscus sabdariffa L.) seeds via supercritical carbon dioxide extraction modified with ethanol was investigated at pressures of 200–400 bar, temperatures from 40 to 80 °C and at supercritical fluid flow rates from 10 to 20 ml/min. It was found that an entrainer such as ethanol could enhance the solubility and extraction yield of roselle seed oil from the seed matrix, compared to values obtained using supercritical CO₂. After a typical run (holding period of 30 min, continuous flow extraction of 3 h), the results indicate that the oil recovery was optimal with a recovery of 108.74% and a phytosterol composition of 7262.80 mg kg^?1 at relatively low temperature of 40 °C, a high pressure of 400 bar and at a high supercritical fluid flow rate of 20 ml/min in the presence of 2 ml/min EtOH as entrainer. The solubility of roselle seed oil increased with temperature at the operating pressures of 200, 300 and 400 bar. Supercritical fluid extraction involved a short extraction time and the minimal usage of small amounts of entrainer in the CO₂.     

Measurement and correlation of quaternary solubilities of dihydroxybenzene isomers in supercritical carbon dioxide

The equilibrium quaternary solubilities of dihydroxybenzene (resorcinol + pyrocatechol + hydroquinone + SCCO₂) isomers were experimentally determined at 308, 318 and 328 K over a pressure range of 9.8–15.7 MPa by using a saturation method. The effects of temperature, pressure and the components on each other have been thoroughly investigated. The selectivity of SCCO₂ for ternary (resorcinol + pyrocatechol + SCCO₂) and quaternary systems was discussed. A new model equation for quaternary solubilities of solids has been developed by accounting for non-idealities by combining the solution model with Wilson activity coefficient model. The model equation has five adjustable parameters and correlates the quaternary solubilities of current data along with two other quaternary data reported in the literature.     

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.     

High-pressure phase equilibria for the binary system carbon dioxide + dibenzofuran

The experimental solubility of dibenzofuran in near-critical and supercritical carbon dioxide and the solid–liquid–vapor (SLV) equilibrium line for the CO₂ + dibenzofuran system are reported. The built in-house static view cell apparatus used in these measurements is described. The solubility of naphthalene in supercritical CO₂ and the CO₂ + naphthalene SLV line are also determined in order to assess the reliability and accuracy of the measurement technique. The solubility of dibenzofuran in carbon dioxide is determined at 301.3, 309.0, 319.2, 328.7 and 338.2 K in the 6–30 MPa pressure range. Solubility data are correlated using the Chrastil model and the Peng–Robinson equation of state. This equation is also used to predict the CO₂ + dibenzofuran SLV line. Results show the feasibility of using supercritical CO₂ to extract dibenzofuran.     

Extraction of oil and β-sitosterol from peach (Prunus persica) seeds using supercritical carbon dioxide

Oil was extracted from the peach (Prunus persica) seeds by supercritical carbon dioxide. Principal phytosterols (stigmasterol, campesterol and β-sitosterol) that have been known to have cholesterol lowering properties were investigated in the extracted oil. Based on gas chromatography–mass spectrometry (GC–MS) analysis, β-sitosterol was identified in the peach seed oil. The effects of temperature, pressure, flow rate of supercritical CO₂, mean particle size of the seeds and extraction time on the amounts of extracted oil and β-sitosterol were investigated. Supercritical fluid extractions were performed in a range of 35–55 °C, 160–240 bar, 4–8 ml CO₂/min, 0.3–1.7 mm and 1–4 h for mentioned parameters. The results indicated that the amounts of oil and β-sitosterol extracted from the peach seeds were optimal with values of 35.3 g/100 g seed and 1220 mg/kg seed respectively at 40 °C, 200 bar, 7 ml/min, 0.3 mm and 3 h.     

Canola oil extracted by supercritical carbon dioxide and a commercial organic solvent

Samples of crushed and cooked canola seeds (Okapy Double Zero) were extracted using supercritical carbon dioxide (SCCO₂) (34.0 MPa and 40.0 °C) and a commercial organic solvent (AW406). Oil solubility was obtained through several stepwise extractions under the conditions of this study, and then three additional extractions were performed to measure fatty acid compositions, iodine values, chlorophyll concentrations and unsaponifiable matter. The yield of SCCO₂ extraction was lower than that after extraction with AW406 solvent, due to the incomplete SCCO₂ extraction process. Fatty acid composition analysis showed that the SCCO₂‐extracted oil was slightly higher in polyunsaturated fatty acids and lower in erucic and behenic acids. However, iodine values and unsaponifiable matter did not indicate significant differences (p >0.05) in the two extracted oils. The chlorophyll concentration of SCCO₂‐extracted oil was lower than that in the AW406 solvent, and as a result, the color of SCCO₂‐extracted oil was lighter.     

Lipase Catalyzed Synthesis of Medium-chain Biodiesel from Cinnamonum camphora Seed Oil

The non-edible camphor tree seed oil was extracted and catalyzed by immobilized lipase for biodiesel production. The oil yield from camphor tree seeds reached 35.2% of seed weight by twice microwave-assisted extractions. Gas chromatography showed that free fatty acid content in camphor tree seed oil was 1.88%, and the main fatty acids were capric acid (53.4%) and lauric acid (38.7%). With immobilized lipase Candida sp. 99–125 as catalyst, several important factors for reaction conditions were examined through orthogonal experiments. The optimum conditions were obtained: water content and enzyme loading were both 15% with a molar ratio of 1:3.5 (oil/ethanol), and the process of alcoholysis was in nine steps at 40 °C for 24 h, with agitation at 170 r·min^− 1. As a result, the medium-chain biodiesel yield was 93.5%. The immobilized lipase was stable when it was used repeatedly for 210 h.     

Continuous extraction rate measurements during supercritical CO2 drying of silica alcogel

We investigated the kinetics of supercritical CO₂ (SCCO₂)-based drying of silica aerogels, a common, but time consuming and energy intensive step in their manufacture. An apparatus was developed to continuously measure alcohol extraction rates from alcogels as a function of key process variables by two redundant techniques. Kinetics data are reported for the drying of 2.5 mm, 5 mm, and 7.5 mm thick annular alcogels by pumping SCCO₂ through a 10 mm-thick concentric annulus surrounding their exterior. The SCCO₂ was at a temperature of 323 K and a pressure of 12.4 MPa and its mass flow rate varied from 1 kg/h to 5 kg/h. Gel thickness and SCCO₂ flow rate were both shown to significantly effect drying rate and required drying time. The results of a conjugate mass transfer model assuming pure diffusion in the alcogel compared favorably with the data when the composition dependence of molecular diffusivity was captured utilizing available correlations.     

Supercritical carbon dioxide extraction of Gac oil

Supercritical carbon dioxide extraction of Gac (Momordica cochinchinensis Spreng) aril was performed at pressures ranging from 200 to 400 bar, temperatures from 313 to 343 K and specific flow rates from 50 to 90 kg h⁻¹ CO₂ kg⁻¹ Gac aril. Total oil recovery and carotenes concentration were investigated in the course of extraction. Mathematical modelling of oil solubility data was also performed. The results showed that at specific flow rate of 70 kg h⁻¹ kg⁻¹, pressure of 400 bar and temperature of 343 K, Gac oil recovery exceeded 95% after 120 min of extraction. Gac oil loading of supercritical carbon dioxide was successfully described by Chrastil's model. Carotenes concentration of extracted Gac oil was found at level of thousands of ppm.     

Extraction of protocatechuic acid from Scutellaria barbata D. Don using supercritical carbon dioxide

The use of supercritical carbon dioxide (SC⿿CO₂), with water as a modifier, was evaluated in this study as a method to extract protocatechuic acid (PA) from Scutellaria barbata D. Don. The highest extraction yield of PA, 64.094 ± 2.756 μg/g of dry plant, was achieved at 75 °C and 27.5 MPa, with the addition of 15.6% (v/v) water as a modifier. The mean particle size was 0.355 mm, the CO₂ flow rate was 2.2 mL/min (STP) and the dynamic extraction time was 100 min. At pressures of 16.2⿿30.0 MPa and temperatures of 45⿿75 °C, the mole fraction solubilities of PA in SC⿿CO₂ ranged from 2.829 ÿ 10^⿿7 to 9.631 ÿ 10^⿿7. The solubility data for PA fit well in the Chrastil model. It is evident that the SC⿿CO₂ extraction uses less solvent, saves both energy and time and is an environmentally friendly extract technology that can be used in the food, cosmetic and pharmaceutical industries.     

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.     

Extraction of bioactive enriched fractions from Eruca sativa leaves by supercritical CO2 technology using different co-solvents

Supercritical fluid extraction from freeze-dried Eruca sativa leaves is assessed with the aim of studying the feasibility to obtain bioactive enriched fractions containing different classes of valuable compounds. Total extraction yields and compositions using pure CO₂ and CO₂ + selected co-solvents are compared. Overall extraction curves, fitted by the model of broken and intact cells developed by Sovová, are reported and the influence of the main parameters that affect the extraction process is analysed. The extract with the highest content in glucosinolates and phenols was collected at 30 MPa and 75 °C using 8% (w/w) of water with respect to the CO₂ flow rate, whereas the fraction richest in lipids was obtained using 8% (w/w) of ethanol as co-solvent at 45 °C and 30 MPa. A process including a first step with supercritical CO₂ extraction using water as co-solvent followed by a second step, where a fraction rich in lipids is extracted using ethanol as co-solvent, is proposed. SCCO₂ results are compared with Soxhlet and other methods that combine organic solvents with ultrasounds.