Characterization and processing of cottonseed oil obtained by extraction with supercritical carbon dioxide

Extraction of flaked cottonseed with supercritical carbon dioxide at temperatures of 50–80 C and pressures of 8,000–15,000 psi yields an improved crude cottonseed oil compared to those obtained by conventional solvent or expeller processes. Improvements include lighter initial color, less refining loss and lighter refined bleached colors. Crude cottonseed oils obtained by supercritical fluid extraction require less refining lye and show less tendency to undergo color fixation while in storage. Presented at the AOCS annual meeting, Chicago, May 1983.     

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.     

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.     

Deacidification of olive oils by supercritical carbon dioxide

An investigation of the application of supercritical carbon dioxide (SC-CO₂) extraction to the deacidification of olive oils has been made to verify that the nutritional properties of the oil remain unchanged when this technique is applied. Preliminary runs at 20 and 30 MPa in the temperature range of 35–60°C were performed on fatty acids and triglycerides as pure compounds or mixtures, to determine their solubility in SC-CO₂. The solubility data obtained show that CO₂ extracts fatty acids more selectively than triglycerides under specific conditions of temperature and pressure (60°C and 20 MPa). It has been noted that the physical state of the solutes plays an important role in determining the solubility trends as a function of temperature and pressure. Extraction of free fatty acids from olive oil was performed on samples with different free fatty acid (FFA) contents at 20 and 30 MPa and at 40 and 60°C. Experimental data suggest that the selectivity factor for fatty acids is higher than 5 and increases significantly as the fatty acid concentration of the oil decreases. For a FFA content of 2.62%, the selectivity reaches a value of 16. In order to evaluate any variations in the composition, several SC-CO₂ extractions of husk oil with high FFA content (29.3%) were made. The results show that selectivity is still significant (≈5) and the composition in the minor component of the deacidified oil has not changed. On the basis of the experimental results and preliminary process evaluations, the authors conclude that SC-CO₂ extraction could be a suitable technique for the deacidification of olive oils, especially for oils with relatively high FFA (<10%).     

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.     

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.     

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.     

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。     

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.     

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.     

Simulation of a supercritical carbon dioxide extraction plant with three extraction vessels

Although SuperCritical (SC) Fluid Extraction (SCFE) has been successfully applied commercially the last three decades, there is no systematic procedure or computational tool in the literature to scale-up and optimize it. This work proposes an algorithm to simulate dynamics in a multi-vessel (≥3) high-pressure SCFE plant where extraction vessels operate in batches, and is thus forced to use simulated-countercurrent flow configuration to improve efficiency. The algorithm is applied to a three-vessel SCFE plant using a shrinking-core model to describe inner mass transfer in the substrate. As example, the extraction of oil from pre-pressed seeds using SC CO₂ at 313 K and 30 MPa is simulated. After three cycles the process reaches a pseudo-steady-state condition that simplifies the estimation of plant productivity. Use of a three- instead of two-vessel SCFE plant increases oil concentration in the stream exiting the plant and decreases CO₂ usage at the expense of increasing extraction time.     

Metal extraction of a spiked solid with supercritical carbon dioxide

A mixture of D2EPHA (Di-2-Ethyl Hexyl Phosphoric Acid) and n-hexane is used as the extractant solution to extract cobalt ions from a fireproof board in the environment of supercritical carbon dioxide. It is found that the cobalt on the spiked sample can be totally removed in a pilot unit. The influence of the carbon dioxide flow rate, the flow rate of the extractant solution, the ratio of D2EHPA to hexane in the extractant solution, the temperature and the replacement of hexane by methanol are investigated in this study. Upon extraction, the cobalt complex with D2EHPA is precipitated with the extractant solution in a separation tank through depressurization, and the amount of extracted cobalt in the separation tank is sampled and analyzed by ICP-OES. The accumulation of the removed cobalt along the extraction time is plotted as an extraction curve, and a kinetic model is established to predict the extraction. It is found that the kinetic model reasonably fits the experimental data. From the model, it is concluded that the metal extraction depends on reactivity, that the extent of the extraction is determined by the reversible reaction of the ion-exchange between D2EHPA and the cobalt ions and that the adsorption kinetics of the extractant in the environment of supercritical carbon dioxide may play an important role in the initial stage of extraction. The proposed model, which successfully provides an easy and accurate prediction for metal extraction from a porous solid matrix, can help to reveal the extraction mechanism and optimize the operational conditions for future scale-up designs.     

Optimization of Ferulago Angulata oil extraction with supercritical carbon dioxide

In this study, the essential oil of aerial parts of a species of a plant called Ferulago Angulata was extracted by CO₂ to optimize the results of the supercritical extraction process and then the essence was analyzed by the method of GC/MS. This extraction has been performed using Taguchi testing method and choosing L16 array in a laboratorial pilot under the following: pressure (90, 120, 140, and 190 bar), temperature (35, 40, 45, and 55 °C), the average particles size (250, 500, 710, and 2000 μm), flow rate (3, 5, 7, and 12 ml/s) and dynamic time (25, 50, 70, and 120 min). Then optimizing process was done to achieve maximum yield extraction. The optimizing conditions are as follows: 190 bar, 35 °C, 710 μm, 12 ml/s, supercritical flow rate 12 ml/s and the final yield is 0.853%. The total yield of supercritical extraction in the mentioned conditions as well as empirically is 0.97% or about 1%. This is the first report announcing optimization of the operation of supercritical extraction of Ferulago Angulata in a laboratorial condition. In the last report of the same authors, which was also for the first time, the chemical components of this plant essence were identified through supercritical extraction and then were compared with the extraction components of other traditional methods.     

Modeling of soybean oil bed extraction with supercritical carbon dioxide

Dry-milled soybeans are extracted with supercritical carbon dioxide at pressures 270 to 375 atm, temperature 50 to 70‡C, solvent flow rates 0.025 to 0016 cm/sec as a linear velocity in the bed-at supercritical state, and three types of soybean particle size in the range 0.05 to 0.2828 cm. Under these conditions, extraction rates of soybean oil from solid substrates in a fixed bed (1.1 mm I.D. x 200 mm Height) have been determined. The extraction rates were constant during the initial extraction period where the film resistance controls the rates, and then, the rales shifted to time-dependent diffusion controlling mass transfer mode. To correlate these features, mass transfer calculations were carried our for the constant rate period and the subsequent unsteady mass transfer rate period, respectively.     

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.     

Characterization and supercritical carbon dioxide extraction of walnut oil

Walnut (Juglans regia L.) oil was extracted with compressed carbon dioxide (CO₂) in the temperature range of 308 to 321 K and in the pressure range of 18 to 23.4 MPa. The influence of particle size was also studied at a superficial velocity of 0.068 cm/s, within a tubular extractor of 0.2 L capacity (cross-sectional area of 16.4 cm²). FFA, sterol, TAG, and tocopherol compositions were not different from those of oil obtained with n-hexane. The main FA was linoleic acid (56.5%), followed by oleic acid (21.2%) and linolenic acid (13.2%). The main TAG was LLL (linoleic, linoleic, linoleic) (24.4%), followed by OLL (oleic, linoleic, linoleic) (19.6%) and LLLn (linoleic, linoleic, linolenic) (18.4%). The main component of sterols was β-sitosterol (85.16%), followed by campesterol (5.06%). The amount of cholesterol was low (0.31 and 0.16% for oils extracted by n-hexane and supercritical fluid extraction, respectively. The CO₂-extracted oil presented a larger amount of tocopherols (405.7 μg/g oil) when compared with 303.2 μg/g oil obtained with n-hexane. Oxidative stability determined by PV and the Rancimat method revealed that walnut oil was readily oxidized. Oil extracted by supercritical CO₂ was clearer than that extracted by n-hexane, showing some refining. A central composite, nonfactorial design was used to optimize the extraction conditions using the software Statistica, Version 5. The best results were found at 22 MPa, 308 K, and particle diameter (Dp) −0.1 mm.     

超临界CO2萃取的研究与应用

介绍了超临界流体的特性及其萃取的基本原则,讨论了超临界流体萃取技术的优点,评述了超临界CO2的特点,概述了国内外超临界CO2萃取技术在医药,食品,香料,石油化工以及环境保护等领域的开发及应用。     

Continuous supercritical carbon dioxide processing of palm oil

Crude palm oil was processed by continuous supercritical carbon dioxide. The process reduces the contents of free fatty acids, monoglycerides and diglycerides, certain triglycerides, and some carotenes. The refined palm oil from the process has less than 0.1% free fatty acids, higher carotene content, and low diglycerides. Solubility of palm oil in supercritical carbon dioxide increased with pressure. A co-solvent improves the refining process of palm oil.