超临界二氧化碳萃取咖啡因的研究进展

超临界二氧化碳萃取咖啡因高新技术经历了由理论的提出到工业的应用 ,由间歇法到半连续法生产的发展历程。我国科技工作者利用此项技术创造性地开发了茶叶综合利用方法 ,在提取的不同阶段 ,在超临界流体中添加不同的添加溶剂来提取出茶叶中的咖啡因以及茶叶中富含的茶多酚、芳香精油、嘌呤类生物碱等宝贵成分     

Supercritical carbon dioxide extraction of CLA-ethyl ester

Supercritical carbon dioxide (SC-CO₂) extraction of Conjugated linoleic acid (CLA) ethyl ester was investigated at pressures in the range of 9 to 10.5 MPa and temperature gradients ranging from 0°C to 21°C. The content of CLA-ethyl ester in the fraction was analyzed with gas chromatography (GC). The experimental results indicated that the rate of extraction would rise with the increase of pressure when temperature gradient was given. Moreover, the extraction pressure had insignificant influence on the selectivity of CLA-ethyl ester in SC-CO₂. When pressure was fixed, setting certain temperature gradient can improve the selectivity of CLA-ethyl ester in SC-CO₂, and CLA-ethyl ester can be concentrated more effectively than without a temperature gradient. The acid value and peroxide value of the fractions were reduced obviously, compared to the raw material. The optimal condition is pressure at 10 MPa and temperature gradient at 11°C.     

Supercritical carbon dioxide extraction of fatty and waxy material from rice bran

Waxy and fatty materials were removed from rice bran by supercritical carbon dioxide at pressures up to 28 MPa and temperatures between 40 and 70°C. The yields of the supercritical extraction were only 16–60% of those obtained by Soxhlet extraction with hexane. The highest yield was reached at the highest pressure and temperature used (28 MPa and 70°C), indicating that supercritical extraction of this lipid-bearing material could probably be improved at more severe extraction conditions. The supercritical extract obtained at operational conditions giving high yield was chromatographically characterized. Compared to the hexane extract, the supercritical extract was lighter in color and richer in wax content and long-chain fatty acids C₂₀−C₃₄. Triacontanol was the most abundant alcohol in both extracts. Tocopherol contents were similar.     

Supercritical carbon dioxide extraction of lipids from Pythium irregulare

Lipids that contain polyunsaturated fatty acids (PUFA) have therapeutic value. PUFA, however, degrade in high-temperature, oxygen-rich conditions typical of conventional hot solvent-extraction and distillation methods. Supercritical CO₂ extraction was chosen as an alternative method to recover these valuable compounds from the lower fungus, Pythium irregulare. Freeze-dried biomass was subjected to an aqueous phase and placed into a flow-through extraction apparatus. Extraction of oil from this biomass showed some success for moisture contents as high as 30% (wet basis). The addition of a novel CO₂-philic surfactant to the wet biomass with moisture contents as high as 95% (wet basis) increased the extraction rate of fungal oil by more than an order of magnitude. For tests with extraction times of 5 to 6 h, data for the diffusion-controlled region were modeled with an analytical solution to Fick’s second law. Equilibrium data were also obtained for the fungal oil at two isotherms (40 and 60°C) over a pressure range of 13.7 to 27.5 MPa.     

Supercritical carbon dioxide extraction in membrane formation by thermally induced phase separation

In this study, a novel and environmentally friendly extracting method, supercritical carbon dioxide (SC‐CO₂) extraction, was investigated in the thermally induced phase separation (TIPS) process for making microporous membranes. In the SC‐CO₂ extraction, the effects of extraction time, pressure, and temperature on the extraction fraction, membrane morphology, and membrane performance were investigated. It was concluded that with extraction conditions of 18 MPa, 35°C and 2 h, the porous membrane had the highest extraction fraction. There was a close relationship between membrane performance and the extraction conditions of SC‐CO₂, and it is possible to tailor membrane performance through the choice of extraction conditions. Compared with traditional solvent extraction, a dry membrane treated by SC‐CO₂ extraction has much less shrinkage and greater water permeability, whereas the degree of crystallization of a membrane extracted by SC‐CO₂ is slightly greater than that extracted by ethanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1632–1639, 2007     

Supercritical CO2 extraction of essential oils and cuticular waxes from peppermint leaves

Essential oils and cuticular waxes were extracted from peppermint leaves with supercritical carbon dioxide in a semicontinuous-flow extractor. The effects of CO₂ flow rate and pressure on the extraction rate were studied within the flow rate range of (4·1–9·8) × 10⁻⁵ kg s⁻¹ and the pressure range of 10–30 MPa. Flow rate effect indicated that the intraparticle diffusion resistance was not dominant in this process. The extraction rate of cuticular waxes increased remarkably with the pressure, whereas that of essential oils was almost constant as compared with cuticular waxes. The concentration of cuticular waxes at the exit of the extractor was close to the solubility of triacontane while that of essential oils was much lower than the solubility of 1-menthol.     

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.     

Preparation and characterization of soy protein isolate films modified with sorghum wax

The effect of increasing the concentration of sorghum wax paste on the characteristics of soy protein isolate (SPI) films was investigated. Water vapor permeability (WVP), tensile strength (TS), elongation at break (E), and total soluble matter (TSM) of cast SPI films were determined. Sorghum wax paste extracted with ethanol was added to film-forming solutions of SPI at 5, 10, 15, or 20% w/w of protein. As the concentration of wax paste increased, mean WVP, E, and TSM values of SPI-sorghum-wax-paste composite films decreased and were lower than those of control SPI films. Mean TS values were lower than the control upon addition of 5 and 10% wax paste; however, TS values increased at 15 and 20% was concentrations. Although no differences in components of sorghum wax were observed between paste extracted with ethanol and wax extracted with hexane, paste extracted with ethanol was miscible with the filmforming solution. SPI-sorghum wax paste films had better water barrier and physical properties compared to control films.     

超临界CO_2流体萃取植物油的实验研究

建立了一套超临界流体萃取实验装置,就大豆和花生两种植物油超临界流体萃取进行了较为详细的实验研究.在探讨了压力、温度、颗粒度、空隙率以及时间等对萃取率的影响之后,获得了指导实际生产的最佳工艺参数条件.     

Supercritical carbon dioxide extraction of squalene and tocopherols from amaranth and assessment of extracts antioxidant activity

Squalene and tocopherols are the most important bioactive constituents in lipophilic amaranth fraction. Therefore, developments of processes of isolation of amaranth extracts enriched with these compounds are of interest. In this study the lipophilic fraction of amaranth seeds was extracted by supercritical fluid extraction with carbon dioxide (SCE-CO₂) under different pressure conditions and by adding 2 and 5% of cosolvent ethanol. The yield of extract varied from 1.37 (15 MPa without cosolvent) to 5.12% (55 MPa and 5% of cosolvent). The highest content of unsaponifiables (21.1%) in the extract was at 55 MPa and 5% of cosolvent; at these conditions the yields of tocopherols and squalene from amaranth seeds were 317.3 mg/kg and 0.289 g/100 g, respectively. Tocopherol isomers in amaranth oil were distributed at the approximate ratio of 1(α-T):27(β-T):6.5(γ-T):5(δ-T). The extract was fractionated in the two separators by gradual decrease of the pressure and it was found that the fraction obtained at ambient conditions contained the highest concentration of tocopherols (up to 7.6 mg/g) and squalene (up to 17.9 g/100 g oil). The highest antioxidant activity measured by the L-ORAC assay possessed the fractions with the highest concentrations of squalene and tocopherols and obtained at 15 MPa with pure CO₂ (235.1 μmol TE/g) and 2% of cosolvent (257.6 μmol TE/g).     

Supercritical carbon dioxide extraction of spearmint oil from mint-plant leaves

Spearmint oil (essential oil of Mentha spicata) was extracted from Turkish mint-plant leaves using supercritical CO₂ in a basket-type extractor. Effects of temperature, pressure, extraction time, amount of CO₂, and entrainer (ethanol) concentration on composition of essential-oil extracts and oil yield, relative to hydro-distillation, were investigated. Relative yields were as high as 80%. Monoterpenes fraction in extracts was inversely correlated with relative oil yields. Monoterpenes were preferentially extracted by CO₂ due to their high vapor pressure, low molar mass and low polarity. Supercritical extraction presented advantages over the conventional hydro-distillation by yielding extracts lower in monoterpenes fraction and by enabling high yields at temperatures safe for the heat-sensitive essential oil.     

Supercritical solvents. Carbon dioxide extraction of retained pyridine from pyridine extracts of coal

Pyridine extracts of coal are excellent models for studies of coal structure and reactions, but the pyridine that is retained is undesirable. A method is described, using supercritical carbon dioxide, for the removal of retained pyridine from pyridine extracts of Illinois No. 6 and Western Kentucky No. 9 coals.     

Supercritical carbon dioxide extraction ofDimorphotheca pluvialis oil seeds

The possibility of extraction ofDimorphotheca oil with supercritical carbon dioxide is demonstrated in this article. Before extraction, the seeds have to be pretreated to improve extraction yield. Experiments showed that the best pretreatment procedure forDimorphotheca was heating the seeds under reduced pressure to 100°C for 60 min, followed by flaking or milling. To give an impression about the efficiency of the supercritical extraction, a mathematical model has been developed to estimate the overall mass transfer coefficient (A _p K). Also, an empirical relation betweenA _p K and the interstitial velocity has been found. The physical properties of the supercriticalDimorphotheca oil are in good agreement with those of conventionally extracted oil, except for a lower phospholipid content. It is expected that further refining of supercriticalDimorphotheca oil will be marginal.     

Combined extraction processes of lipid from Chlorella vulgaris microalgae: microwave prior to supercritical carbon dioxide extraction

Extraction yields and fatty acid profiles from freeze-dried Chlorella vulgaris by microwave pretreatment followed by supercritical carbon dioxide (MW-SCCO(2)) extraction were compared with those obtained by supercritical carbon dioxide extraction alone (SCCO(2)). Work performed with pressure range of 20-28 Mpa and temperature interval of 40-70 °C, gave the highest extraction yield (w/w dry weight) at 28 MPa/40 °C. MW-SCCO(2) allowed to obtain the highest extraction yield (4.73%) compared to SCCO(2) extraction alone (1.81%). Qualitative and quantitative analyses of microalgae oil showed that palmitic, oleic, linoleic and α-linolenic acid were the most abundant identified fatty acids. Oils obtained by MW-SCCO(2) extraction had the highest concentrations of fatty acids compared to SCCO(2) extraction without pretreatment. Native form, and microwave pretreated and untreated microalgae were observed by scanning electronic microscopy (SEM). SEM micrographs of pretreated microalgae present tearing wall agglomerates. After SCCO(2), microwave pretreated microalgae presented several micro cracks; while native form microalgae wall was slightly damaged.     

The Solubility of Styrene from Polystyrene in Supercritical CO2

The solubility of styrene from polystyrene in supercritical carbon dioxide is measuredat 323 K,333 K,and 343 K in the pressure range from 12 to 28 MPa.Based on the associationconcept and the theory of dense gas sorption in polymers,a displacement and association mechanismon supercritical fluid extraction of the monomer from the polymer is proposed.And,a novel math-ematical model for correlating the solubility data obtained from the experiments is also proposed inthe paper.     

Properties, composition, and analysis of grain sorghum wax

Grain sorghum wax has been judged to be a potential source of natural wax with properties similar to carnauba wax. Approximately 0.16–0.3% (w/w) wax can be extracted from grain sorghum depending on the efficiency of the organic solvents. Although the melting points of carnauba wax and sorghum wax are similar, i.e., 78–86 and 77–85°C, respectively, they differ in acid values, i.e., 2–10 and 10–16, respectively, and saponification numbers, i.e., 77–95 and 16–49, respectively. Improved knowledge of the properties, composition, and analysis of grain sorghum wax would assist in efforts for industrial application of this product. Major components of sorghum wax are hydrocarbons, wax esters, aldehydes, free fatty alcohols, and FFA. The hydrocarbons consist mainly of C₂₇ and C₂₉, and the aldehydes, alcohols, and acids are mainly C₂₈ and C₃₀. The wax esters are mostly esters of C₂₈ and C₃₀ alcohols and acids.     

超临界二氧化碳流体萃取玉米胚芽油

用超临界ＣＯ２流体技术对玉米胚芽油的萃取进行了研究，考察了温度、压力对得油率的影响，初步探讨了分离器的温度、压力以及萃取原料对油品质量的影响。     

The Solubility of Styrene from Polystyrene in Supercritical CO2

The solubility of styrene from polystyrene in supercritical carbon dioxide is measured at 323 K, 333 K, and 343 K in the pressure range from 12 to 28 MPa. Based on the association concept and the theory of dense gas sorption in polymers, a displacement and association mechanism on supercritical fluid extraction of the monomer from the polymer is proposed. And, a novel mathematical model for correlating the solubility data obtained from the experiments is also proposed in the paper.     

超临界CO_2萃取青皮挥发油的工艺研究

采用正交实验法对超临界CO2萃取中药青皮挥发油的最佳工艺条件进行优选。以挥发油得率为考察指标,探讨了萃取压力、萃取温度、萃取时间三因素在不同水平下对青皮挥发油得率的影响,并与水蒸气蒸馏法进行了比较。研究表明,萃取压力对挥发油得率有显著影响,萃取温度及时间影响不显著,各因素作用主次关系为:压力>温度>时间。优选得到的最佳工艺为:萃取压力25 MPa,萃取温度35℃,萃取时间1.5 h,得率为1.3197%,比水蒸气蒸馏法提高2.4倍,时间减少78.57%。超临界CO2萃取收率高、耗时短、品质好。     

Supercritical carbon dioxide and solvent extraction of 2-acetyl-1-pyrroline from Pandan leaf: The effect of pre-treatment

Pandan (Pandanus amaryllifolius Roxb.) leaf is a source of natural flavoring widely used in South-east Asia. The major compound contributing to the characteristic flavor of Pandan is 2-acetyl-1-pyrroline (2AP). This highly volatile compound also contributes significantly to the flavor of aromatic rice such as basmati and jasmine rice. As the consumer requirement for use of natural flavors, extraction of components from natural sources has been sought. In this study, supercritical carbon dioxide (SC-CO₂) and solvent extraction of components from Pandan leaves were performed. Experimental parameters included particle size and drying method (oven and freeze drying). Results indicated that the initial value of moisture content and particle size of Pandan leaves had the greatest effect on the total yield and 2AP concentration of the extracts. Almost 80% of water in Pandan leaves can be removed by drying. Yields of supercritical extracts were 10 times lower when compared to the hexane extracts. The total yield of extracts was increased up to 50% with decreasing particle size of Pandan leaves. Extraction of coarsely ground freeze-dried Pandan leaves by SC-CO₂ obtained the highest yield (0.88 ± 0.06%) followed by oven dried (0.38 ± 0.09%) and fresh leaves (0.34 ± 0.01%). The 2AP was identified by GC-MS and analyzed by GC-FID. Supercritical and hexane extracts of pre-treated Pandan leaves were found to have a small quantity of 2AP ranging between 0.04 ± 0.01 and 0.45 ± 0.01 ppm. Grinding pre-treatment was the best method for both SC-CO₂ and hexane extractions while the freeze drying method was the best for SC-CO₂.