Supercritical fluid extraction of oil from millet bran

Proso millet bran [Panicum miliaceum (L.)], variety Dakota White, was extracted with supercritical carbon dioxide (SC-CO₂) to yield crude oil. The effects of operating parameters (pressure, temperature, and specific solvent flow) and of features of the raw material (moisture content and particle size) on oil extraction were investigated. Complete de-oiling of ground millet bran pellets was achieved under 300 bar at 40°C with a specific solvent flow of 2–10 h⁻¹ within 200 to 500 min. Solvent requirements were 20–30 kg CO₂/kg raw material. Composition of crude SC-CO₂ oil extracted under optimal conditions, i.e., fatty acid profile, amount of unsaponifiables, tocopherols, free fatty acids, sterols, sterol esters, waxes, hydrocarbons, and phospholipids, was compared to that of crude oil obtained by petroleum ether extraction. These two oils were similar in terms of fatty acid profile and amount of free fatty acids, unsaponifiables, peroxides, and tocopherols. They differed in respect to phospholipids (present in petroleum etherextracted oil and absent in SC-CO₂ extracted oil), metals, and waxes (lower levels in SC-CO₂ extracted oil). The effects of extraction procedures on oxidative stability of crude SC-CO₂ oil were studied. Ensuring that all pieces of the extractor in contact with the oil were in stainless steel; cleaning the separator, i.e., washing with KOH, rinsing, purging with N₂ and CO₂, and heating; performing a couple of extractions before the main extraction; and achieving the extraction without interruption all positively influenced the oxidative stability of the oil. Conversely, increasing CO₂ purity above 99.5% had no effect. Oxidative stability of the SC-CO₂ oil extracted under these conditions was only slightly lower than that of the oil extracted with petroleum ether.     

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.     

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.     

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.     

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.     

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 extraction of borage seed oil coupled to conventional solvent extraction of antioxidants

This paper describes the extraction of borage seed oil by supercritical carbon dioxide (SC-CO₂) and the further extraction of antioxidants from the SC-CO₂-defatted borage meal with organic solvents (water, methanol, ethanol and ethyl acetate). The optimal conditions for oil extraction were obtained at 303 and 323 K at 200 bar, 2.5 h and a continuous flow of CO₂ of 1.5 L/h introduced through the bottom when the operating pressure and temperature were reached, attaining a yield of 60%. Borage oil is rich in unsaturated fatty acids; oleic acid, linoleic acid and linolenic acid accounted for 74% of the total fatty acid content under the above conditions. The highest extraction yield was achieved using water or methanol as extracting solvent from the SC-CO₂-defatted borage meal at 303 K and pressures of 200 and 150 bar for water and methanol, respectively. The most potent extracts, according to all methods tested, were obtained with water and methanol.     

Quality of residual oil from palm-pressed mesocarp fiber (Elaeis guineensis) using supercritical CO2 with and without ethanol

The qualities of oils extracted from fresh and dried palm-pressed mesocarp fiber were evaluated. The means of extraction included conventional solvent extraction and supercritical carbon dioxide (SC-CO₂) extraction with and without addition of ethanol. Extraction efficiency using pure SC-CO₂ and the effect of moisture content on efficiency were studied. Minor components, such as vitamin F, carotenoids, squalene and phytosterols, obtained by different methods were compared. The quality of oil recovered from fresh palm-pressed fiber is generally better than that of oil recovered from dried fiber. The SC-CO₂ extraction rate was lower for fresh fiber than for dried fiber. The incorporation of ethanol with SC-CO₂ resulted in oil with higher oxidative stability than did SC-CO₂ alone. Concentrations of minor components and the acylglycerol compositions of the oils extracted from both types of fibers were similar.     

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.     

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.     

Properties and processing of corn oils obtained by extraction with supercritical carbon dioxide

Crude oils were extracted from wet- and dry-milled corn germs with supercritical carbon dioxide (SC-CO₂) at 50–90 C and 8,000–12,000 psi and were characterized for color, free fatty acids, phosphorus, refining loss, unsaponifiable matter, tocopherol and iron content. They were compared with commercial products. Extraction of wetmilled germ with SC-CO₂ has some advantages over the conventional prepress solvent method commonly used in the industry. For example, SC-CO₂ extraction of wet-milled germ at 50 C and 8,000 psi yields crude oil with a lower refining loss and a lighter color. After laboratory processing, a light-colored, bland salad oil is obtained. Crude, refined, bleached and deodorized oils from SC-CO₂-extracted dry-milled germ appear equivalent to those obtained by expeller pressing. Presented in part at AOCS meeting, Toronto, Ontario, Canada, May 1982.     

The Fractionation of Shea Nut Oil Using Supercritical Carbon Dioxide — A Feasibility Study for the Extraction of Oil from Gum

Supercritical carbon dioxide (SC-CO₂) successfully extracted triglycerides from crude Shea nut oil (Butyrospermum parkii) at temperatures of 40–80°C and pressures of 100–400 bar. Selective removal of free fatty acid, mono- and di-glycerides, iron, triterpene acetates, triterpene cinnamates and polyisoprenoid gum from triglyceride was achieved by varying the solvent power of the SC-CO₂. Triglyceride so produced had a higher stability to oxidation than the crude oil. Polyisoprenoid gum was essentially insoluble in SC-CO₂. The extraction partially fractionated the triglycerides according to their carbon numbers.     

Solubility of fatty acids in supercritical carbon dioxide

The solubilities of lauric, linoleic, myristic, oleic, palmitic and stearic acid in supercritical carbon dioxide (SC-CO₂) at different pressures and temperatures were measured. The solubility values obtained in this work were compared with previously published data, and possible causes for observed discrepancies were discussed. The solubilities of the six fatty acids were modeled by Chrastil’s equation, and estimated model parameters were used to plot the solubility isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO₂ density. The comparison of solubility isotherms of fatty acids and vegetable oil suggests that separation of fatty acids from triglycerides might be possible by using SC-CO₂ at densities less than 700 kg/m³. From the effect of temperature on fatty-acid and vegetable-oil solubility, it seems that the extraction yield could be increased without sacrificing the selectivity of SC-CO₂ for fatty acids by choosing a higher operating temperature. The data also suggest that fractionation of certain fatty acids might be possible by manipulating the processing conditions. Given the values of the constants, Chrastil’s equation could serve as a guideline for choosing appropriate processing conditions and predicting the effect of pressure and temperature of SC-CO₂ on solute solubility.     

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.     

Petroleum-free extraction of oil from soybeans with supercritical CO2

Full-fat soyflakes are readily extracted with supercritical carbon dioxide (SC-CO₂) at pressures of 3,000~10,000 psig and 50 C. Under these conditions, SC-CO₂ has the density of a liquid and the diffusivity of a gas. Therefore, equilibrium solubility is readily achieved in a short-path batch extractor which permits high gas flow rates. Soybean oil extracted with SC-CO₂ is lighter in color and contains less iron and about one-tenth the phosphorus of hexane-extracted crude oil from the same beans. The lower phosphorus content is reflected in a chromatographic refining loss of 0.6% compared to 1.9% for hexane crude. Refined oils from hexane and SC-CO₂ extraction had equivalent odor and flavor scores initially and after 4 days' storage at 60 C. Carbon dioxide, an ideal solvent for extraction of food products, is low-cost and readily available from fermentation processes and could free over 20 million gallons of costly hexane per year for essential energy uses.     

Biodiesel production from supercritical carbon dioxide extracted Jatropha oil using subcritical hydrolysis and supercritical methylation

This study investigates supercritical carbon dioxide (SC-CO₂) extraction of triglycerides from powdered Jatropha curcas kernels followed by subcritical hydrolysis and supercritical methylation of the extracted SC-CO₂ oil to obtain a 98.5% purity level of biodiesel. Effects of the reaction temperature, the reaction time and the solvent to feed ratio on free fatty acids in the hydrolyzed oil and fatty acid esters in the methylated oil via two experimental designs were also examined. Supercritical methylation of the hydrolyzed oil following subcritical hydrolysis of the SC-CO₂ extract yielded a methylation reaction conversion of 99%. The activation energy of hydrolysis and trans-esterified reactions were 68.5 and 45.2 kJ/mole, respectively. This study demonstrates that supercritical methylation preceded by subcritical hydrolysis of the SC-CO₂ oil is a feasible two-step process in producing biodiesel from powdered Jatropha kernels.     

1,8-cineol-rich Cardamom Seed (Elettaria cardamomum) Extracts Using Green Technologies and Conventional Extractions: Process Analysis,Phytochemical Characterization,and Food Application

Extract from cardamom seeds (Elettaria cardamomum) having highest content of 1,8-cineol was obtained by supercritical carbon dioxide (SC-CO₂) with a sample size of 25 g at 50°C, 200 bar after 90 min at a flow rate of 2 L/min of gaseous CO₂, compared to those obtained by hydro-distillation, organic solvent, liquid CO₂, and subcritical CO₂ extractions. This extract had the best combination of phytochemical properties such as phenolic content, reducing power, antioxidant activity, anti-inflammatory, and antimicrobial potency. Cardamom extract-enriched custard was formulated using this extract which showed promise as a nutraceutical product.     

Cosolvency effect of SF6 on the solubility of poly(tetrafluoroethylene‐co‐19 mol % hexafluoropropylene) in supercritical CO2 and CHF3

Cloud‐point data to 280°C and 2800 bar are reported for a binary mixture of poly(tetrafluoroethylene‐co‐19.3 mol % hexafluoropropylene) (FEP₁₉) in fluoroform (CHF₃) and for ternary mixtures of FEP₁₉–CHF₃–sulfur hexafluoride (SF₆) and FEP₁₉–CO₂–SF₆. FEP₁₉ does not dissolve in CHF₃ at a temperatures less than 235°C due to strong dipolar CHF₃–CHF₃ interactions relative to FEP₁₉–CHF₃ cross interactions. However, FEP₁₉ dissolves in CO₂ if the temperature is greater than ≈185°C and the pressure is in excess of 1000 bar. When SF₆ is added to either FEP₁₉–CO₂ or FEP₁₉–CHF₃ mixtures, the cloud‐point curve is shifted to lower pressures and temperatures due to the increase in favorable dispersion interactions with nonpolar FEP₁₉. The magnitude of the shift in cloud‐point pressure per amount of SF₆ added to solution decreases in a nonlinear manner with increasing amounts of SF₆. The Sanchez‐Lacombe equation of state can model the binary FEP₁₉‐SCF data if the FEP₁₉–CO₂ and FEP₁₉–CHF₃ binary interaction parameters are allowed to vary with temperature. However, a poor representation is obtained for the ternary phase behavior. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2039–2045, 1999     

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%.     

超临界CO2萃取丁香油的数值模拟

为了预测超临界CO₂萃取挥发油动态过程,根据挥发油在超临界CO₂与物料之间的质量传递平衡,采用集总参数法建立超临界CO₂萃取丁香油过程的数学模型。结合不同温度、压力、粒径和CO₂流速条件下的实验结果,对方程进行了合理的简化,并利用实验数据拟合出模型中CO₂密度、粒径和流速的系数。验证结果表明模型的计算值和实验值的平均相对误差在6. 88%～57. 78%之间,建立的数值模型能较好地描述实际的超临界CO₂萃取丁香油行为。