6. Conclusion

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]. In Table 7, some published works that used supercritical CO2 to

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

Some of its applications are in food, nutraceutical, and cosmetic industries, and in the production of lubricants, biodiesel, and glycerol [94–96]. 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 CO2 extraction [98]. Table 8 shows some studies that used supercritical CO2 to obtain the main classes of the FA group.

The extraction with supercritical CO2 modified with water in different proportions is carried out to obtain bioactive compounds of high polarity, because as mentioned above, CO2 is an

Raw material Carotenoid References

Fucoxanthin, astaxanthin, lutein, and β-carotene [87]

Tomato juice Lycopene and β-carotene [84] Hemerocallis disticha Lutein and zeaxanthin [85] Dunaliella salina 9-cis and trans-β-carotenes [86]

Fucus serratus and Laminaria digitata Xanthophyll and fucoxanthin [88]

Raw material Fatty acid Reference Cucurbita ficifolia, Bouché ω6-linoleic acid, palmitic acid, oleic acid [100] Farfantepenaeus paulensis Palmitic acid, oleic acid, stearic acid, palmitoleic acid, and linoleic acid [101] Cannabis sativa L. Linoleic acid and linolenic acid [102] Chaetoceros muelleri Myristic acid, palmitic acid, and palmitoleic acid [103] Saw Palmetto Lauric acid, mystiric acid, and oleic acid [104]

diabetes [90], hypertension [91], coronary diseases [92], and inflammation [93].

5.5. Extraction with supercritical CO2 modified with ethanol/water

obtain carotenoids are shown.

228 Carbon Dioxide Chemistry, Capture and Oil Recovery

Undaria pinnatifida, Haematococcus pluvialis, and

Table 7. Published studies about carotenoid extraction using CO2

Table 8. Published studies about fatty acids extraction using CO2

Chlorella vulgaris

5.4. Fatty acids extraction

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, cosolvent, 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.
