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%.     

Lampante olive oil refining with supercritical carbon dioxide

Lampante olive oil has been treated in a supercritical CO₂ extraction plant operating in a continuous countercurrent mode. We report the results of a systematic investigation to define the optimal operative parameters. We also have examined the compositional variation of lampante olive oil samples with different characteristics and of different geographic origins before and after refining at optimal conditions. Although practical feasibility of the proposed procedure can be questioned, the results demonstrate the possibility of fractionating components contained in the starting oil even if present at trace levels.     

Characterisation of acorn oils extracted by hexane and by supercritical carbon dioxide

Acorn fruit oils from two species of oak, Quercus rotundifolia L. (holm‐oak) and Quercus suber L. (cork‐oak), were extracted by n‐hexane. The acorn fruit of Quercus rotundifolia L. was also extracted by supercritical CO₂ at 18 MPa and 313 K, a superficial velocity of 2.5 × 10^?4 ms^?1, and a particle size diameter of 2.7 × 10^?4 m. The oils were characterised in terms of fatty acids, triglycerides, sterols, tocopherols, and phospholipids. The main fatty acid in both fruit species was oleic acid (about 65%), followed by linoleic acid (about 16.5–17%) and palmitic acid (about 12.1–13.4%). The main triglyceride found in acorn oils was the OOO (oleic, oleic, oleic) triglyceride (33–38%), followed by the POO (palmitic, oleic, oleic) triglyceride (12.6–18.2%). In terms of sterols, the main component in acorn oils of both species was β‐sitosterol (83.5–89%), followed by stigmasterol (about 3%). However, in Quercus suber L., acorn oil was found to consist to 10.2% of campesterol. The amount of cholesterol was low (0.27% for the Quercus rotundifolia L. oil extracted by supercritical fluid extraction, and 0.18% for the oil extracted by n‐hexane). The Quercus suber L. acorn oil presented 0.1% of cholesterol. The total amount of tocopherols in Quercus rotundifolia L. acorn oils was almost the same when the oil was extracted by n‐hexane (973 mg/kg oil) or by supercritical CO₂ (1006 mg/kg oil). The Quercus suber L. acorn oil presented a high value of total tocopherols (1486 mg/kg oil). The supercritical CO₂ did not extract the phospholipids. The amount of phospholipids was very similar for both species of oak acorn oils extracted by n‐hexane. Oxidative stability was also studied, by using the peroxide value and the Rancimat method, revealing that all the oils were significantly protected against oxidation. The influence of storage, under several conditions, on the oxidative stability was also studied. The Quercus rotundifolia L. oil extracted by n‐hexane was better protected against oxidation after a few days of storage at 60 °C.     

Interfacial tension of edible oils in supercritical carbon dioxide

Interfacial properties essentially influence fluid‐liquid separation processes. Thereby, interfacial tension is an important parameter that is associated with mass transfer and mutual solubility of participating compounds. For this reason, interfacial tension of a virgin olive oil with a known amount of free fatty acids was measured in supercritical carbon dioxide atmosphere at 313 K and 353 K and pressures up to 40 MPa. The obtained values were compared to different oils some of which contain appreciable amounts of volatile components. In general, interfacial tension behaviour is dominated by the effect of pressure, whereas differences between oil compositions are secondary. Besides mutual solubility interfacial tension is supposed to be associated with the compressibility of the dense fluid phase. For predicting mass transfer area some general comments on the colloidal behaviour of systems containing supercritical CO₂ are made     

Methanolysis of seed oils in flowing supercritical carbon dioxide

The direct methanolysis of triglycerides in flowing supercritical carbon dioxide by an immobilized lipase is described. The reaction system consists of two syringe pumps for substrate addition and another two syringe pumps for delivering CO₂ at 24.1 MPa. Corn oil is pumped into the carbon dioxide stream at a rate of 4 μL/min, and methanol is pumped at 5 μL/min to yield fatty acid methyl esters (FAME) at >98% conversion. Direct methanolysis of soy flakes gives FAME at similar yields. This combined extraction/reaction is performed at 17.2 MPa and 50°C. The fatty acid profiles obtained for these seed oils matches those obtained by classical chemical synthesis.     

Conversion of oils to monoglycerides by glycerolysis in supercritical carbon dioxide media

Glycerolysis of soybean oil was conducted in a supercritical carbon dioxide (SC-CO₂) atmosphere to produce monoglycerides (MG) in a stirred autoclave at 150–250°C, over a pressure range of 20.7–62.1 MPa, at glycerol/oil molar ratios between 15–25, and water concentrations of 0–8% (wt% of glycerol). MG, di-, triglyceride, and free fatty acid (FFA) composition of the reaction mixture as a function of time was analyzed by supercritical fluid chromatography. Glycerolysis did not occur at 150°C but proceeded to a limited extent at 200°C within 4 h reaction time; however, it did proceed rapidly at 250°C. At 250°C, MG formation decreased significantly (P<0.05) with pressure and increased with glycerol/oil ratio and water concentration. A maximum MG content of 49.2% was achieved at 250°C, 20.7 MPa, a glycerol/oil ratio of 25 and 4% water after 4 h. These conditions also resulted in the formation of 14% FFA. Conversions of other oils (peanut, corn, canola, and cottonseed) were also attempted. Soybean and cottonseed oil yielded the highest and lowest conversion to MG, respectively. Conducting this industrially important reaction in SC-CO₂ atmosphere offered numerous advantages, compared to conventional alkalicatalyzed glycerolysis, including elimination of the alkali catalyst, production of a lighter color and less odor, and ease of separation of the CO₂ from the reaction products.     

Oxidative stability of walnut oils extracted with supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO₂) was used to partially defat walnuts, and the oxidative stability of the extracted walnut oils was assessed. The SC-CO₂-extracted oils were less stable during accelerated storage in the dark than was pressed walnut oil, as determined by PV, headspace analysis by solid-phase microextraction, and sensory methods. The SC-CO₂-extracted oils, however, exhibited greater photo-oxidative stability than did pressed walnut oil by all of these methods, possibly because of the presence of chlorophyll in the pressed oil. Oxidative stability indices and tocopherol contents were significantly lower in the SC-CO₂-extracted oils than in pressed oil.     

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.     

Oxidative stability of seed oils extracted with supercritical carbon dioxide 1

Dry-milled corn germ, soybean and cottonseed flakes were extracted (at 70-90 C and 12,000 psi) with supercritical carbon dioxide (SC-CO₂) to yield crude oils. Oxidative stability of the crude oils was determined and compared to similar products obtained by conventional expeller and/or prepress solvent extraction. Under Schall oven storage conditions (60 C), SC-CO₂-extracted oils undergo rapid deterioration and fail to show the normal induction period observed with conventional expeller and solvent-extracted crude oils. The levels of tocopherols found in SC-CO₂-extracted oils are comparable to those obtained by expeller or solvent extraction, while phospholipids present in significant amounts in conventional crude oils are essentially absent from SC-CO₂-processed crudes. The addition of phosphatides to SC-CO₂-extracted crude oils improves oxidative stability, which suggests that both tocopherols and phospholipids are required to stabilize crude oils against autoxidation. Heating of SC-CO₂-extracted crude oils to deodorization temperatures improves oxidative stability. The destruction of fat hydroperoxides under these conditions probably accounts for improved oxidative stability. A combination of heat and the addition of citric acid and phenolic antioxidants resulted in further improvement of oxidative stability. Presented at the American Oil Chemists’ Society Annual Meeting in Philadelphia, PA, in May 1985.     

Lipase-catalyzed randomization of fats and oils in flowing supercritical carbon dioxide

Enzymes can frequently impart more selectivity to a reaction than chemical catalysts. In addition, the use of enzymes can reduce side reactions and simplify post-reaction separation problems. In combination with an environmentally benign and safe medium, such as supercritical carbon dioxide (SC-CO₂), enzymatic catalysis makes supercritical fluids extremely attractive to the food industry. In this study, randomization of fats and oils was accomplished with an immobilized lipase in flowing SC-CO₂. Triglycerides, adsorbed onto Celite, are solubilized in CO₂ and carried over 1–10 g immobilized lipase derived from Candida antarctica. The degree of randomization and rate of triglyceride throughput could be controlled by CO₂ pressure and flow rate and quantity of enzyme used. The dropping points and solid fat indices of the resulting randomized oils were compared to oils that were randomized by conventional methods with sodium methoxide. Reversed-phase high-performance chromatography with flame-ionization detection was used to quantitate changes in triglyceride composition of various substrates, such as palm olein and high-stearate soybean oil. The resultant randomized oil mixtures have properties, e.g., solid fat index, that make them potential candidates for incorporation into traditional margarine formulations.     

Concentration of sterols and tocopherols from olive oil with supercritical carbon dioxide

A process based on the use of a semicontinuous countercurrent supercritical fluid extraction has been developed to isolate and concentrate minor compounds, such as sterols and tocopherols, from olive oil. In the present work, an evaluation of the efficiency of different random packing materials (Raschig rings, Dixon rings, Fenske rings, and glass beads) to selectively separate sterols and tocopherols from olive oil has been performed. Parameters such as recovery, enrichment, and selectivity vs. TG are discussed. Considering the importance of supercritical fluid extraction as a clean processing technology and the interest in minor compounds with nutraceutical properties from olive oil, the process studied represents an alternative to the reuse of low-quality olive oil to extract high added-value products.     

Hydrogenation of vegetable oils using mixtures of supercritical carbon dioxide and hydrogen

Hydrogenation of vegetable oils under supercritical conditions can involve a homogeneous one-phase system, or alternatively two supercritical components in the presence of a condensed phase consisting of oil and a solid catalyst. The former operation is usually conducted in flow reactors while the latter mode is more amenable to stirred, batch-reactor technology. Although many advantages have been cited for the one-phase hydrogenation of oils or oleochemicals using supercritical carbon dioxide or propane, its ultimate productivity is limited by the oil solubility in the supercritical fluid phase as well as unconventional conditions that affect the hydrogenation. In this study, a dead-end reactor has been utilized in conjunction with a head-space consisting of either a binary fluid phase consisting of varying amounts of carbon dioxide mixed with hydrogen or neat hydrogen for comparison purposes. Reaction pressures up to 2000 psi and temperatures in the range of 120–140°C have been utilized with a conventional nickel catalyst to hydrogenate soybean oil. Depending on the chosen reaction conditions, a wide variety of end products can be produced having different iodine values, percentage trans fatty acid content, and dropping points or solid fat indices. Although addition of carbon dioxide to the fluid phase containing hydrogen retards the overall reaction rate in most of the studied cases, the majority of products have low trans fatty acid content, consistent with a nonselective mode of hydrogenation.     

Elastomeric foam prepared by supercritical carbon dioxide

Biodegradable elastomer poly[(1,4‐butylene terephthalate)‐co‐(1,4‐butylene adipate)] foam was successfully prepared using supercritical CO₂. The elastomer foam has closed and uniform cell structure with density about 90 g/L. Narrow size distribution with average cell diameter 32 μm were obtained. The foamed balls show rubbery properties and can recover well (>90%) to their original shape quickly after releasing press stress. Cell growth needs to take place at melting state where the migration and orientation of polymer chains are permanently kept without remained force of springback. Some unique phenomena were observed during foaming the elastomer: post‐expansion (about 40%) was obtained after removing the foamed samples from a cylinder mold, which results in forming a ball rather than a cylinder like the mold. This phenomenon was explained by the lower glass transition temperature of the elastomer, in which residual CO₂ foam continuously in the room temperature; and “memory” of internal strength. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44354.     

Controlling cellular morphology by supercritical carbon dioxide

A series of high‐performance porous materials, including open‐cell and closed‐cell foams, were prepared by a two‐stage batch foaming process from fluorinated poly(arylene ether)s, and the porous morphology was characterized with scanning electron microscopy. The effects of saturation pressures, saturation temperatures, transfer times, molecular structures, and solvent traces on the cell sizes, cell densities, and bulk densities of porous materials were examined. According to the conclusions, the porous structures could be controlled with cellular sizes between the nanoscale and microscale. All nanoporous materials have dielectric constants in the ultralow‐dielectric‐constant range (1.4–2.0). The open structures can be prepared by two methods, and there are two kinds of morphologies from the two methods, including foams with small, spotlike openings (diameters between 10 and 100 nm) in the cell walls and bicontinuous nanoporous foams. Another special method for controlling the porous morphology was used here. Films with closed‐cell microcellular foams were placed in supercritical carbon dioxide again. The original morphology of the microcellular foam collapsed. The collapsed morphology was also characterized with scanning electron microscopy, and three kinds of cellular morphology were observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of biodiesel from edible and non-edible oils in supercritical alcohols and enzymatic synthesis in supercritical carbon dioxide

Biodiesel is an attractive alternative fuel because it is environmentally friendly and can be synthesized from edible and non-edible oils. The synthesis of biodiesel from edible oils like palm oil and groundnut oil and from crude non-edible oils like Pongamia pinnata and Jatropha curcas was investigated in supercritical methanol and ethanol without using any catalyst from 200 to 400 °C at 200 bar. The variables affecting the conversion during transesterification, such as molar ratio of alcohol to oil, temperature and time were investigated in supercritical methanol and ethanol. Biodiesel was also synthesized enzymatically with Novozym-435 lipase in presence of supercritical carbon dioxide. The effect of reaction variables such as temperature, molar ratio, enzyme loading and kinetics of the reaction was investigated for enzymatic synthesis in supercritical carbon dioxide. Very high conversions (>80%) were obtained within 10 min and nearly complete conversions were obtained at within 40 min for the synthesis of biodiesel in supercritical alcohols. However, conversions of only 60–70% were obtained in the enzymatic synthesis even after 8 h.     

Kinetic modeling of the glycerolysis reaction for soybean oils in supercritical carbon dioxide media

Production of MAG by glycerolysis is important for food, pharmaceutical, and cosmetic industries. Conducting glycerolysis in supercritical carbon dioxide (SC-CO₂) media has advantages over conventional alkali-catalyzed glycerolysis. However, kinetic data are lacking for such conversions in the presence of SC-CO₂. The objectives of this study were to estimate the rate constants and elucidate the mechanism for the glycerolysis of soybean oil in SC-CO₂ using previously reported data. The data were taken from experiments using soybean oil, glycerol (glycerol/oil molar ratios of 15–25) and water (3–8% w/w) in SC-CO₂ at 20.7–62.1 MPa and 250°C for a 4 h period. Rate constants for the parallel glycerolysis and hydrolysis reactions were estimated for each processing parameter (glycerol/oil, water content, pressure) by minimizing the summed squared error between the values calculated from the experimental data and those obtained from the kinetic model. The results suggested that water and pressure had an effect on rate constants but the glycerol/oil ratio did not. Findings provide the kinetic modeling data necessary for the optimization of supercritical processes involving glycerolysis reactions for the production of MAG from vegetable oils.     

Fat-soluble vitamin extraction by analytical supercritical carbon dioxide

Extraction of fat-soluble vitamins (A, D, E, and β-carotene) by supercritical carbon dioxide (SC-CO₂) was tested to replace conventional liquid extraction methods, which require large volumes of organic solvents. Supercritical fluid extraction (SFE) is a rapid extraction technique for fat-soluble vitamins enabling them to be accurately determined using only small volumes of organic solvents. Extractions were performed on ultra-high-temperature sterilized milk, milk powder, pork, liver paté (paté de fois), infant formula, and canned baby food to compare the methods. The proposed method is based on the extraction of fat-soluble vitamins and their esters by using SC-CO₂ with methanol as a modifier. HPLC analysis using photometric detection was used for the vitamin analysis. The results showed no significant differences between extraction methods. The proposed SFF method appears to be useful as a substitute for the traditional organic solvent method, mainly for vitamin A and γ-tocopherol. Some data in this paper were presented at the 5th International Symposium on Supercritical Fluids, Atlanta, Georgia, April 2000.     

超临界CO2萃取丁香挥发油的实验研究

采用正交实验法对超临界CO2萃取丁香挥发油的条件进行了研究。考察了萃取温度、压力、CO2流量等因素在不同水平下对丁香挥发油提取率的影响。得到了超临界C02萃取丁香挥发油的最佳实验条件：萃取压力30MPa、温度40℃、CO2流量40kg／h和萃取时间80min,得率为20．62％。与水蒸气蒸馏法比较,超临界CO2萃取的收率高,萃取时间短。     

Separation of fish oils ethyl esters by means of supercritical carbon dioxide: Thermodynamic analysis and process modelling

A semicontinuous fractionation process of fish oil ethyl esters was carried out in this work by means of supercritical carbon dioxide. The process focused on the separation of ethyl esters on chain length basis. Experimental temperature ranged from 42 to , whereas pressure ranged from 10.1 to 17.2 MPa. Optimal operating conditions were found for solvent density in the range 570-. A thermodynamic model based on the Peng-Robinson equation of state, proposed to represent high-pressure phase equilibria for this complex system, was validated on the experimental data. The model assumes that the multicomponent natural mixture can be considered as composed of five major components, defined on chain length basis. The proposed thermodynamic model was then used in the modellization of a continuous multistage fractionation process. The continuous process simulations that were carried out allowed to investigate the effect of number of theoretical stages, reflux ratio and solvent to feed ratio on the distribution of the components between extract and raffinate. A case study was considered, in order to find out process operating conditions to attain 95% by weight of heavy components (acid chain length 20 and 22) in the raffinate together with a 95% recovery. Results show that the stated separation is possible with a solvent to feed ratio and a number of theoretical stages in the range 90-150 and 11-30, respectively. The simulations were also employed to study the effect of the operating conditions of the separator used for solvent recycling.     

Comparison of essential oils compositions of Nepeta persica obtained by supercritical carbon dioxide extraction and steam distillation methods

Essential oil of Nepeta persica cultivated in Iran was obtained by steam distillation and supercritical (carbon dioxide) extraction methods. The oils were analysed by capillary gas chromatography using flame ionization and mass spectrometric detections. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters such as pressure, temperature, modifier volume and extraction times (dynamic and static) on the supercritical fluid extraction (SFE) of N. persica oil were investigated. The results showed that under the pressure of 20.3 MPa, temperature of 45 °C, methanol of 1.5% v/v), dynamic extraction time of 50 min and static extraction time of 25 min extraction was more selective for the 4αβ,7α,7aα-nepetalactone. Twelve compounds were identified in the steam-distilled oil. The major components of N. persica were 4αβ,7α,7aα-nepetalactone (26.5%), cis-β-farnesene (4.4%) and 3,4α-dihydro-4aα,7α,7aα-nepetalactone (3.5%). However, by using supercritical carbon dioxide under optimum conditions, only two components have more than 90.0% of the oil. The extraction yield based on steam distillation was 0.08% (v/w). On the other hand, using SFE extraction yield in the range of 0.22–8.90% (w/w) were obtained at different conditions. The results show that, in Iranian N. persica oil, 4αβ,7α,7aα-nepetalactone is a major component.