Supercritical CO2 Extraction of Essential Oil from Origanum Vulgare L.: Experiments and Mathematical Modeling

In this work, the supercritical CO₂ extraction of essential oil from Origanum Vulgare L. was investigated and modeled. An orthogonal test and ANOVA indicated that extraction pressure, extraction temperature, and extraction time had significant influence on extraction effects. Based on experiments, a mathematical model depended on mass conservation equation was established to describe and simulate supercritical CO₂ extraction of essential oil from Origanum Vulgare L. The mean diameter, accumulation properties, and the inside and outside transfer properties of extracted material particles were considered in the model. The model was solved numerically with the finite difference method and Runge-Kutta method synthetically. Model estimation was validated with small scale experimental data. Moreover, the effects of extraction pressure, extraction temperature, extraction time, concentration, and the flow rate of the entrainer on mass of essential oil were investigated using the model.     

Experimental studies and discrete thermodynamic modeling on supercritical CO2 extractions of a hexadecane and crude oil

Continuous multiple-contact experiments using a supercritical CO₂ were performed to study the phase equilibrium behavior of the dynamic extractions of a hexadecane and crude oil. The extraction yields increased as CO₂ density increased with a pressure rise at constant temperature. The rates of extractions were also greater at higher pressure. The simulated distillation analysis of extracted crude oil samples represented that the earlier extracts contained lighter compounds and the latter extracts contained progressively heavier compounds. These compositional changes occurring during a dynamic extraction were also ascertained by phase-equilibrium flash calculations using the equations of state and a pseudo-component lumping method. Two different equations of state, Soave-Redlich-Kwong and Peng-Robinson, were used to predict the equilibrium compositions of the extract phase that is a supercritical carbonic phase. The results of phase behavior calculations established the nature of the extraction and partitioning process as a function of time. These results also provided reasonable agreement between the experimental data and the calculated values.     

Supercritical carbon dioxide extraction of cottonseed with co-solvents

Extraction of cottonseed lipids with supercritical carbon dioxide (SC-CO₂) was conducted with and without a cosolvent, ethanol or 2-propanol (IPA). At 7000 psi and 80°C, the reduced pressure, temperature and density of SC-CO₂ was at 6.5, 1.17 and 1.85, respectively; the specific gravity was 0.87. Under these conditions, CO₂ is denser than most liquid extraction agents such as hexane, ethanol and IPA. The extraction of cottonseed with SC-CO₂ gave a yield of more than 30% (moisture-free basis). This is comparable to yields obtained by the more commonly used solvent, hexane. The crude cottonseed oil extracted by SC-CO₂ was visually lighter than refined cottonseed oil. This was substantiated by colorimetric measurements. No gossypol was detected in the crude oil. However, crude oil extracted by SC-CO₂, to which less than 5% of ethanol or IPA as co-solvent was added, containedca. 200 ppm of gossypol, resulting in the typical dark color of cottonseed crude oil with gossypol. CO₂ extracted a small amount of cottonseed phosphatides, about one-third of that extracted by pure ethanol, IPA or hexane. A second extraction with 100% ethanol or IPA after the initial SC-CO₂ extraction produced a water-soluble lipid fraction that contained a significant amount of gossypol, ranging between 1500 and 5000 ppm. Because pure gossypol is practically insoluble in water, this fraction is believed to be made up of gossypol complexed with polysaccharides and phosphatides. Partially presented at the AOCS 1993 Annual Meeting & Expo in Anaheim, California.     

Recovery of Oil,Erucic Acid,and Phenolic Compounds from Rapeseed and Rocket Seeds

Erucic acid‐enriched oil, sought for industrial purposes, from rapeseed (agronomic plant) and rocket seeds (non‐agronomic plant) was extracted by three different processes: supercritical CO₂, mechanical expression, and hexane extraction. Oil extraction yields were determined and the extracted oils were characterized for their fatty acid and phenolic compound compositions. Higher oil yields were achieved using hexane compared to mechanical expression and supercritical CO₂ extractions. Fatty acid analysis indicated a higher content of erucic acid in rapeseed oil than in rocket oil. In addition, supercritical CO₂ extraction allowed better recovery of phenolic compounds with high antioxidant activities. The most prominent identified polyphenols were vanillin, sinapic acid, syringic acid, and apigenin.     

Supercritical CO2 extraction of pigment components with pharmaceutical importance from Chlorella vulgaris

BACKGROUND: Chlorella vulgaris is a green microalgae that contains various pigment components of carotenoids and chlorophylls. Supercritical CO₂ is widely used for extraction of pharmaceutical compounds because it is non‐oxic and easily separated from extracted material by simply depressurizing. In this work, pharmaceutical compounds from Chlorella vulgaris have been extracted using supercritical CO₂ with or without entrainer at various extraction conditions. RESULTS: Based on high performance liquid chromatography (HPLC) analysis, the extracts contained pigment components, such as lutein, β‐carotene, chlorophyll a and b. Higher extraction pressure and temperature promoted higher lutein extraction by supercritical CO₂. The optimum pressure and temperature for extraction were obtained as 50 MPa and 80 °C. Ethanol as an entrainer was more effective than acetone for the extraction of pigment components. Pigment components in the extract obtained by supercritical CO₂ with and without entrainer were compared with the extract obtained by a conventional extraction method. CONCLUSION: Supercritical CO₂ has been successfully applied for the extraction of pigment components from Chlorella vulgaris. Supercritical CO₂ enabled high selectivity for lutein extraction; however, the lutein yield was lower than that obtained by extraction using supercritical CO₂ with ethanol and soxhlet. Copyright © 2008 Society of Chemical Industry     

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.     

Tunisian Pistacia atlantica Desf. Extraction Process: Impact on Chemical and Nutritional Characteristics

Plant materials have been used in different fields such as therapeutics, cosmetics, and energy for ages. Several studies have investigated seeds, whether common or not, in order to ensure a better valuation of natural resources. Among these, Pistacia atlantica Desf. has been the subject of several works on its characterization and valorization. Among the current trends in sustainable development and environmental protection, valorizing natural wild plants via green chemistry has become prevalent. One of these plants, Pistacia atlantica Desf., is a tree that grows in arid and semi-arid areas, notably in Tunisia, and produces seeds rich in oil. In this study extracting the oil from its seeds is tried by three methods (supercritical carbon dioxide (CO₂), pressure, and hexane), and the efficiency of these extraction processes is compared in order to obtain the best yield and maximize its valorization in a variety of industrial fields. The obtained oil is found to be rich in polyunsaturated fatty acids, namely linoleic and oleic acids, with a similar acidic composition among all extraction methods. The tocopherol composition of the oil is determined using high performance liquid chromatography. The total polyphenol content is determined using the Folin-Ciocalteu colorimetric analysis method. The results show that the seed oil of Pistacia atlantica Desf. extracted by supercritical CO₂ gives the highest extraction yield (25%) and the lowest acidity and peroxide values with a high degree of oxidation at 232 and 270 nm. This method also gives the highest content of alpha, gamma, and delta tocopherol as well as total phenolic content compared to the other extraction methods. The composition of chlorophylls and carotenes in the seed oil of Pistacia atlantica Desf. is determined. Besides, the analysis of the sterol composition reveals that β-sitosterol is still prevailing. Among all the tested extracts, the supercritical CO₂ extract demonstrates the best antioxidant performance against the tested radicals. The oil extracted by supercritical carbon dioxide (CO₂) is of a higher quality compared to that extracted by pressure and by hexane. Practical applications : The Pistacia atlantica Desf. oil exhibits interesting physicochemical and biological characteristics. The type of extraction affects the quality of the major and minor components in the seeds. However, the supercritical CO₂ method produces a better oil quality with the presence of antioxidants such as tocopherols and polyphenols. In fact, it is found that the oil extracted by the three methods has an important sterolic profile with the predominance of β-sitosterol. According to the classification of vegetable oils, unsaturated fatty acids of atlas pistachio oil can be categorized as oleo linoleic oil, which enhances its nutritional value. Having these characteristics, the use of this oil can be considered in agrifood products.     

Deacidification of black cumin seed oil by selective supercritical carbon dioxide extraction

The deacidification of high-acidity oils from Black cumin seeds (Nigella sativa) was investigated with supercritical carbon dioxide at two temperatures (40 and 60°C), pressures (15 and 20 MPa) and polarities (pure CO₂ and CO₂/10% MeOH). For pure CO₂ at a relatively low pressure (15 MPa) and relatively high temperature (60°C), the deacidification of a highacidity (37.7 wt% free fatty acid) oil to a low-acidity (7.8 wt% free fatty acid) oil was achieved. The free fatty acids were quantitatively (90 wt%) extracted from the oil and left the majority (77 wt%) of the valuable neutral oils in the seed to be recovered at a later stage by using a higher extraction pressure. By reducing the extraction temperature to 40°C, increasing the extraction pressure to 20 MPa, or increasing the polarity of the supercritical fluid via the addition of a methanol modifier, the selectivity of the extraction was significantly reduced; the amount of neutral oil that co-extracted with the free fatty acids was increased from 23 to 94 wt%.     

Solubility of red pepper (C<Emphasis Type="Italic">apsicum annum</Emphasis>) oil in near- and supercritical carbon dioxide and quantification of capsaicin

Red pepper oil was extracted using near- and supercritical carbon dioxide. Extraction was carried out at pressures ranging from 10 to 35 MPa and temperatures from 30 to 60 °C, with a CO₂ flow rate of 24.01 g/min using a semi-continuous high-pressure extraction apparatus. The duration for extraction was 2 h. The highest oil yield was found at high pressure and temperature. The highest solubility of oil (1.18 mg/g of CO₂) was found at 35 MPa and 60 °C. The solubility data of red pepper oil in near- and supercritical CO₂ were fitted in Chrastil model. The fatty acid composition of red pepper oil was analyzed by gas chromatography (GC). Linoleic acid was found to be the major fatty acid in the oil. Capsaicin was quantified in different extracts by high performance liquid chromatography (HPLC). The highest capsaicin yield was found at 35 MPa and 60 °C.     

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.     

Extraction of lipids from Yarrowia Lipolytica

BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high‐lipid‐content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO₂) extraction using ethanol as a co‐solvent. Also, high pressure solubility measurements in the systems ‘CO₂ + yeast oil’ and ‘CO₂ + ethanol + yeast oil’ were carried out. RESULTS: The solubility experiments determined that, at the conditions of the supercritical extractor (40 °C and 20 MPa), a maximum concentration of 10 mg of yeast oil per g of solvent can be expected in pure CO₂. 10% w/w of ethanol in the solvent mixture increased this value to almost 15 mg of yeast oil per g of solvent. Different pretreatments were necessary to obtain satisfactory yields in the extraction experiments. The Soxhlet and the ASE method were not able to complete the lipid extraction. The ‘SCCO₂ + ethanol’ extraction curves revealed the influence of the different pretreatments on the extraction mechanism. CONCLUSION: Evaluating the effectiveness of a given pretreatment, ASE reduced the amount of material and solvent used compared with Soxhlet. In all three cases, the best total extraction performance was obtained for the ethanol‐macerated yeast (EtM). Addition of ethanol to the solvent mixture enhanced the oil solubility. Oil can be extracted from Y. lipolytica in two different steps: a non‐selective ethanol extraction followed by TAG‐selective SCCO₂ purification. © 2012 Society of Chemical Industry     

Supercritical CO2 Extraction of Essential Oil from Algerian Rosemary (Rosmarinus officinalis L.)

The present study presents experimental results concerning the supercritical CO₂ extraction of essential oil from Algerian rosemary leaves. The effects of key operating parameters such as pressure, temperature, particle size and CO₂ mass flow rate on the extraction yield were investigated. The obtained yields were in the range of 0.95–3.52 g oil/g dry rosemary, and the best value was observed at a pressure of 22 MPa, a temperature of 40 °C, a flow rate of 7 g/min, and a particle size of 1 mm. The performance of the local rosemary used was assessed by comparison of the obtained yields with values reported in the literature for essential oils derived from different rosemary sources. The GC and the GC‐MS analyses showed that the major compound detected in the essential oil was camphor, at 48.89 wt %.     

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.     

Extraction of essential oil from geranium (Pelargonium graveolens) with supercritical carbon dioxide

This study investigated the supercritical fluid extraction (SFE) of geranium essential oil from geranium (Pelargonium graveolens) using supercritical carbon dioxide solvent. The extraction yield was measured as a function of pressure, temperature and carbon dioxide flow rate. At low pressure (10 MPa) and high temperature (343 K), waxes were co‐extracted with the essential oil, resulting in artificially elevated essential oil extraction yields as no method was available with the SFE apparatus used to separate co‐extracted waxes and oil. At high pressure (30 MPa) and low temperature (313 K), the amount of wax co‐extracted decreased. Under these ‘optimum’ conditions, the extraction yield increased with decrease in flow rate giving a maximum extraction yield of 2.53%. All samples were analyzed by gas chromatography–mass spectrometry and the effect of pressure and extraction time on oil composition was studied. The percentage compositions of terpene hydrocarbons, terpenols, geraniol and geranyl esters were significantly affected by pressure and extraction time. The oil samples obtained by SFE were also compared with commercially obtained steam distilled samples. All major components of the commercially obtained oils were present in the SFE‐obtained oils; however, the percentage composition of the major components differed greatly between steam distilled and SFE oils. Copyright © 2005 Society of Chemical Industry     

The Fatty Acid Profile and Phenolic Composition of Descurainia sophia Seeds Extracted by Supercritical CO2

Oil and phenolics were extracted from Descurainia sophia (Sophia) seeds by a supercritical CO₂ system. Extractions were conducted in two sequential steps, first using 100 % CO₂ and then adding 10 % ethanol as co‐solvent. The extracts were collected in each step using two separate collectors operating at different pressures. The extraction run was 3 and 4 h for the first period, and 2 h for the second period. The majority of the oil was collected in the first extraction period while phenolic compounds were obtained in the second extraction period. A combined mode of static/dynamic extraction (3 h running and 1 h soaking in CO₂) was also used in the first extraction period, which enhanced the total extraction yield (29.3 ± 0.5 %) and was comparable to the 4 h extraction yield (31.4 ± 0.1 %). The total fatty acid (FA) content of oil in collector 1 (0.94 g) was nearly twice that in collector 2 (0.60 g). The oil contained 14 FAs with α‐linolenic being predominant (48.5 %), with a total 91.1 % unsaturated FAs, a ω3/ω6 ratio of 2.7, and an erucic acid content of 6.2 %. More than 10 phenolic compounds were detected by HPLC in the Sophia seed extracts of which sinapic acid was the dominant compound. Sophia seed extracts showed high levels of antioxidant activity. These results suggest that Sophia seed oil and phenolics have the potential for functional food and pharmaceutical applications.     

Supercritical fluid extraction of bioactive lipids from the microalga Nannochloropsis sp.

Marine microalgae are recognised as an important renewable source of bioactive lipids with a high proportion of polyunsaturated fatty acids (PUFA), which have been shown to be effective in preventing or treating several diseases. For the extraction of oil from microalgae, supercritical CO₂ (ScCO₂) is regarded with interest, being safer than hexane and offering a negligible environmental impact, a short extraction time and a high‐quality final product. Whilst some experimental papers are available on the supercritical fluid extraction (SFE) of oil from microalgae, only limited information exists on the kinetics of the process. In such a contest, a mathematical model able to describe the kinetics of the SFE was applied to the recovery with ScCO₂ of lipids from Nannochloropsis sp., a marine microalga commonly used in aquaculture and characterised by a lipid fraction with a high PUFA content. The aim of this paper was to examine the effect of operating conditions on the kinetics of the SFE, on process yields and on the fatty acid composition of lipid extracts.     

Supercritical CO2 extraction of oil, carotenoids, squalene and sterols from lotus (Nelumbo nucifera Gaertn) bee pollen

The high-quality oil, abundant in carotenoids, squalene and sterols (mainly consisting of campesterol, stigmasterol, β-sitosterol and β-amyrin), was extracted by supercritical CO₂ from lotus bee pollen for its potential nutraceutical use. The effects of extraction pressure and temperature on the yields and the compositions of the extracts were investigated by using a two-factor central composite rotatable design experiment. ANOVA for response surface model demonstrated that the data were adequately fitted into four polynomial models. The yields of the oil, carotenoids, squalene and sterols were significantly influenced by the experimental variables. It was predicted that maximum oil yield obtained at the extraction pressure of 38.2 MPa and temperature of 49.7 °C contained the maximum amount of carotenoids, squalene and sterols. GC-FID analysis of the fatty acid composition of lotus bee pollen oil showed that polyunsaturated fatty acids accounted for approximately 22% of the total fatty acids.     

Kinetics of supercritical carbon dioxide extraction of borage and evening primrose seed oil

In the present work, high‐pressure extraction of borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) seed oil, containing the valuable γ‐linolenic acid (GLA), has been investigated. Extraction was performed with supercritical carbon dioxide on a semi‐continuous flow apparatus at pressures of 200 and 300 bar, and at temperatures of 40 and 60 °C. A constant flow rate of carbon dioxide in the range from 0.17 to 0.20 kg/h was maintained during extraction. The extraction yields obtained using dense CO₂ were similar to those obtained with conventional extraction using hexane as solvent. The composition of extracted crude oil was determined by GC analysis. The best results were obtained at 300 bar and 40 °C for both seed types extracted, where the quality of oil was highest with regard to GLA content. The evening primrose seed oil extracted with supercritical fluid extraction was particularly rich in unsaturated fatty acids: up to 89.7 wt‐% of total free fatty acids in the oil. The dynamic behavior of the extraction runs was analyzed using two mathematical models for describing the constant rate period and the subsequent falling rate period. Based on the experimental data, external mass transfer coefficients, diffusion coefficients and diffusivity in solid phase were estimated. Results showed good agreement between calculated and experimental data.     

Supercritical fluid extraction of fungal oil using CO2, N2O,CHF3 and SF6

The extraction of oil from fungi (Mortierella ramanniana var.angulispora) was studied using carbon dioxide (CO₂), nitrous oxide (N₂O), trifluoromethane (CHF₃) and sulfur hexafluoride (SF₆) under supercritical conditions. The oil solubility was highest in SC-N₂O followed by SC-CO₂, while both SC-CHF₃ and SC-SF₆ showed poorer solvent power. The recorded oil solubilities at 333 K and 24.5 MPa were 2.3 wt% in N₂O, 0.48 wt% in CO₂, 0.0099 wt% in CHF₃ and 0.0012 wt% in SF₆. The oil solubilities in SC-N₂O and SC-CO₂ were measured over the pressure range 15.7–29.4 MPa and at temperatures ranging from 313–353 K. N₂O always showed greater solvent power than did CO₂ at the same temperature and pressure. The solvent power of a supercritical fluid increases with density at a given temperature, and increases with temperature at constant density. The change in neutral lipid composition of the extracted oil with the extraction ratio was measured. Free fatty acids or diglycerides were extracted more easily than triglycerides or sterol esters. The change in fatty acid composition was also measured. The proportion of γ-linolenic acid in the extract remained constant throughout the extraction.     

Supercritical fluid extraction and characterisation of oil from hazelnut

Hazelnut (Corylus avellana L.) oil was extracted with compressed carbon dioxide in the temperature range of 308—321 K and in the pressure range of 18—23.4 MPa. In addition the influence of the superficial velocity, within a tubular extractor was studied. Physical and chemical characteristics of the oil were obtained. The results including contents of free fatty acids, sterols, triacylglycerols and tocopherols were compared with those obtained when n‐hexane was used as solvent. No significant differences were found when the oils extracted by both methods were analysed. The main fatty acid was the oleic acid (83—85%), followed by linoleic acid (6—8%) and palmitic acid (5—6%). The main triglyceride found in hazelnut oils was the trioleylglycerol (OOO) (63.4—69.6%), followed by the linoleyl‐dioleylglycerol (LOO) (11.6—15.5%) and palmitoyl‐dioleylglycerol (POO) (9.9—10.4%). In terms of sterols, the main component was β‐sitos‐terol (∼83%) followed by campesterol (∼6%). The amount of cholesterol was very low (∼0.2%). The CO₂ extracted oil contained about 17% more tocopherols (458.7 μg/g oil) than the oil extracted by n‐hexane (382.8 μg/g). Oxidative stability was studied by using the induction time determined by the Rancimat method. The oil obtained by supercritical fluid extraction (SFE) was slightly more protected against oxidation (8.7 h for SFE extracted oil and 6.7 h for the hazelnut oil extracted with n‐hexane). Both oils presented high stability index values (7.81 for the oil extracted by n‐hexane and 8.7 for the oil extracted with supercritical CO₂). Oil extracted by supercritical CO₂ was clearer than the one extracted by n‐hexane, showing some refining. Besides, the acidity index was 1.6 for the n‐hexane extracted oil and 0.9 for the oil extracted with supercritical carbon dioxide. The central composite non‐factorial design was used to optimise the extraction conditions, using the Statistica, version 5 software (Statsoft). The best results, in terms of recoveries of hazelnut oil by SFE, were found at 22.5 MPa, 308 K and superficial velocity of 6.0 × 10^—4 ms^—1.