Therefore, high diffusivity and low viscosity lead to a faster extraction time providing a dissolving power so that the supercritical fluid is considered a solvent. The viscosity of a supercritical fluid is smaller than the viscosity of a gas and the diffusivity of the liquid is greater than the diffusivity of a supercritical fluid. The most cited drawback of using supercritical carbon dioxide as solvent is the high investment cost for equipment acquisition and operation.
However, the extraction with supercritical carbon dioxide presents a lower extraction time because of its diffusivity and low surface tension, greater selectivity in the compounds of interest and little or no consumption of organic solvents [ 43 , 44 , 45 , 46 ]. Essential oils have been used to prevent or treat human diseases for several centuries. The extraction of the volatile compounds present in edible or medicinal aromatic plants is generally carried out by hydrodistillation; however, the authors report that some compounds may undergo hydrolysis during the extraction period [ 47 ].
Guan et al. However, when compared with the extraction of eugenol acetate, the extraction with supercritical CO 2 presented higher yields in relation to the other extraction methods.
Extraction of chemically active volatile molecules with supercritical CO 2 is very widespread [ 49 , 50 , 51 ]. This is due to the possible applications as agents that promote biological activities [ 52 ], such as antioxidant activity [ 53 ], anti-inflammatory activity [ 54 ], insecticidal activity [ 55 ], and phytotoxic activity [ 56 ]. Published studies on extraction of essential oils using CO 2 as supercritical fluid. As given above, it is observed that the process of extraction of essential oils using supercritical CO 2 is ecologically a cleaner method than the conventional ones, and it has been seen as one of the most viable alternatives.
Phytosterols plant sterols are non-volatile triterpenes. The great majority of these compounds are formed by carbon with one or two carbon-carbon double bonds [ 62 ]. These compounds have various biological activities such as lowering the total serum or plasma cholesterol levels and the low-density lipoprotein cholesterol levels.
Emergent Properties at High Material Densities
In addition, they have antitumor activities inhibiting the development of colon cancer [ 64 , 65 ]. For the extraction of these phytosterols, the supercritical CO 2 has been shown to be an efficient technique for extraction of fixed oils from vegetable matrices. Studies report that this solvent may be superior to obtain oils in relation to the conventional extraction, exhibiting a recovery rate of phytosterols of A very important parameter for the extraction of phytosterols with supercritical CO 2 is the increase of the pressure, because it favors the solvation power and consequently the solubilization of these compounds, with a recovery rate of up to Carotenoids are tetraterpenes present in plants that have several applications in food [ 72 ], cosmetic [ 73 ], and pharmaceutical [ 74 ] areas.
Some of the benefits provided by these pigments are: antioxidant activity and strengthening of the immune system against degenerative diseases such as cancer, cardiovascular diseases, muscle degeneration, inflammation, hypertension, insulin resistance and obesity [ 75 , 76 ]. Because of their hydrophobic characteristics, carotenoids are usually extracted using organic solvents such as hexane and petroleum ether.
Carotenoids with hydrophilic characteristics can be obtained with more polar solvents such as acetone, ethanol, and ethyl acetate [ 77 ]. The techniques used to extract this compound may be maceration, Soxhlet, microwave-assisted extraction [ 78 , 79 ], ultrasound-assisted extraction [ 80 ], pressurized liquid extraction [ 81 , 82 ], and supercritical fluid technology using low temperature. The process is performed in a short time in relation to conventional processes and does not use toxic solvents to collect the compound of interest [ 83 ].
Fatty acids FA belong to the lipid class and differ according to the size of the C chain 2—80 , the presence or absence of double bonds saturated or unsaturated or their radical function as the groups hydroxyl, epoxy, and halogen atoms [ 89 ]. Ingestion of FA is essential to have an adequate energy balance in the human organism in addition to reducing the risk of some diseases such as diabetes [ 90 ], hypertension [ 91 ], coronary diseases [ 92 ], and inflammation [ 93 ].
Some of its applications are in food, nutraceutical, and cosmetic industries, and in the production of lubricants, biodiesel, and glycerol [ 94 , 95 , 96 ]. Some of the extraction methods that can be used to obtain FA are mechanical extraction [ 97 ], extraction by supercritical fluids and organic solvent [ 98 ], microwave-assisted extraction [ 99 ], and supercritical CO 2 extraction [ 98 ]. As previously mentioned, parameters of processes, such as temperature and pressure, can influence the extraction of bioactive compounds.
Besides these two parameters, anthocyanins are also important for the extraction of phenolic compounds.
Solvent flow rate, percentage of co-solvent, co-solvent type ethanol or water , and extraction time are parameters that directly implicate the yield of these substances at the end of the extraction process [ ]. Further examples of extraction of phenolic compounds using supercritical CO 2 modified with co-solvents can be analyzed in the studies [ , , ]. They extracted various flavonoids like quercetin, catechin, epicatechin from cranberry, blueberry, and raspberry. Carbon dioxide can be safely applied in high-pressure extraction processes due to its numerous advantageous characteristics.
It is neither toxic nor inflammable, being able to act as solvent, co-solvent, or anti-solvent, which allows it to be used in natural products and foodstuff processing that require treatments intending to preserve their nutritional and sensory properties. Since it is a non-polar substance, it is suitable for extraction of non-polar bioactive compounds when used in pure form.
When associated with a polar co-solvent, it can be used for extraction of polar compounds such as phenolic compounds and anthocyanins. Therefore, these characteristics make carbon dioxide the most important fluid used in high-pressure processes for extraction, separation, fractionation, micronization, and encapsulation, applied to obtain concentrated extracts with bioactive compounds for food, pharmaceutical, and cosmetic applications. Costa W. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
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Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract This chapter describes the use of carbon dioxide at high pressures as an alternative for the extraction of bioactive compounds in a more sustainable way, addressing some of its physicochemical properties, such as pressure, temperature, density, solvation, selectivity, and its interaction with the solute when modified by other solvents such as ethanol and water.
Keywords supercritical CO2 high pressure density vegetable matrix bioactive compounds. Introduction Separation technologies with fluids at high pressures are essentially vital to get new natural products of vegetable or marine origin that have biological activity, so-called bioactive extracts. Diagrams of pure substances 2. High-pressure carbon dioxide properties 4. Thermodynamic properties The influence of the density in the solvation power by the tunable operating conditions P, T is the most important thermodynamic effect in the high-pressure fluid processes.
P-V-T diagram calculation with equations of state To describe the P-V-T diagram behavior, it is necessary to use precise equations of state EOS with specific parameters for pure substances. Cubic equations of state. Carbon dioxide density calculated with different equations of state. Other high-pressure carbon dioxide properties The application of the high-pressure fluid extraction technologies in both laboratory and industrial scales requires not only the knowledge of the physical and thermodynamic properties of the solvent, but also requires the understanding of thermal and transport properties behavior.
Order of magnitude of transport properties.
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High-pressure carbon dioxide applications The most cited drawback of using supercritical carbon dioxide as solvent is the high investment cost for equipment acquisition and operation. Essential oil extraction Essential oils have been used to prevent or treat human diseases for several centuries.
Aromatic plant Bioactive compounds References Juniperus communis L. Germacrene D and 1-octadecene. Phytosterols extraction Phytosterols plant sterols are non-volatile triterpenes. Phytosterols extracted using supercritical CO 2. Carotenoid extraction Carotenoids are tetraterpenes present in plants that have several applications in food [ 72 ], cosmetic [ 73 ], and pharmaceutical [ 74 ] areas.
Published studies about carotenoid extraction using CO 2. Fatty acids extraction Fatty acids FA belong to the lipid class and differ according to the size of the C chain 2—80 , the presence or absence of double bonds saturated or unsaturated or their radical function as the groups hydroxyl, epoxy, and halogen atoms [ 89 ]. Linoleic acid and linolenic acid [ ] Chaetoceros muelleri Myristic acid, palmitic acid, and palmitoleic acid [ ] Saw Palmetto Lauric acid, mystiric acid, and oleic acid [ ]. Published studies about fatty acids extraction using CO 2.
Malvasia nera Anthocyanins [ ] Arrabidaea chica Anthocyanins and luteolin [ ] Scutellaria lateriflora L. Baicalin, dihydrobaicalin, lateriflorin, ikonnikoside I, scutellarin, oroxylin A 7-O-glucuronide, oroxylin A, baicalein, wogonin [ ] Vaccinium myrtillus L.
Delphinidin 3-O-galactoside, delphinidin 3-O-glucoside, cyanidin 3-O-galactoside, delphinidin 3-O-arabinoside, cyanidin 3-O-glucoside, petunidin 3-O-galactoside, cyanidin 3-O-arabinoside, petunidin 3-O-glucoside, peonidin 3-O-galactoside, petunidin 3-O-arabinoside, peonidin 3-O-glucoside, malvidin 3-O-galactoside, peonidin 3-O-arabinoside, malvidin 3-O-glucoside, malvidin 3-O-arabinoside and malvidin 3-O-xyloside [ ]. Conclusion Carbon dioxide can be safely applied in high-pressure extraction processes due to its numerous advantageous characteristics.
Acknowledgments Costa W. More Print chapter. How to cite and reference Link to this chapter Copy to clipboard.
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