For the Originality in Extraction

Supercritical carbon dioxide (sCO2) is the most widely used fluid for the Supercritical Fluid Extraction (SCFE) process across the globe. Not only is sCO2 capable of extracting the required ingredients in their pristine form, the prime reason for the surging popularity of SCFE, it also makes the process more manageable, economical, and safe.

Figure 1. Buffalo Extraction Systems Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) Plant [1]

These days, “clean label” products are selling like hot cakes. Increasingly health conscious customers are placing a premium on natural ingredients in the food, pharmaceutical, beverage, and neutraceutical products they consume. Now, clean label is a broad term with various meanings – organic, natural, locally grown, non-GMO . . . the list goes on. Some even take it to link its maker to more transparent work practices [2].

Alternative processes such as Solvent Extraction and Hydrodistillation leave behind harmful residues. Plus, they distort the ingredient being extracted. That is, the ingredient does not retain its natural purity. Regulations have caught up with public demand and impose exacting conditions to ensure the quality and safety of products by limiting toxic residues. One more reason to rely on CO2 SCFE.

What Makes Supercritical Carbon dioxide (sCO2) an Exceptional SCFE Solvent?

Carbon dioxide and water are the most widely employed supercritical fluids [3]. sCO2 makes such a useful supercritical fluid because it [4]:

  • Has a critical temperature of 31.10C, which is around the ambient temperature improving its compatibility with temperature-sensitive compounds;
  • Has a more manageable critical pressure of 73.9 bar;
  • Is non-flammable and non-toxic;
  • Has a customizable density to upgrade its solvent power;
  • Is available in ample quantities and in pure form; and
  • Has a comparatively low cost.

Although CO2 is a greenhouse gas (GHG), the SCFE process using CO2 becomes eco-friendly if the gas is captured from the atmosphere and recycled.

Carbon dioxide Supercritical Fluid Extraction (CO2 SCFE)

Solvent Extraction employs organic solvents to dissolve the ingredient from the raw material. Later, it separates the organic solvent from the dissolved ingredient. The problem is, organic solvents do not completely disassociate from the ingredient, leaving behind residues [5].

Parameter Solvent Extraction SCF Extraction
Solvent traces in final product Yes Zero
Heavy metal content in final product Yes Zero
Inorganic salt content in final product Yes Zero
Similarity with the actual components to be extracted in terms of Colour and Flow Characteristics Less: because polar compounds get dissolved. More: because low operating temperatures and selective extraction of CO2.

Table 1. SCFE Vs Solvent Extraction

That is, the ingredient loses its natural purity. What is more, it may develop a certain degree of toxicity. But the concerns on using organic solvents for extraction go beyond toxicity for the individual. Some solvents are ozone depleting substances [6] and their use negatively impacts the environment.

Hydrodistillation i.e. the use of water and steam distillation inherently employs heat, something that thermally degrades the ingredients [7]. Again, the ingredient, when extracted, is no longer available in its pure form.

Parameter Steam Distillation SCF Extraction
Extraction of essential, non-volatile oils Not possible Possible
Extraction of highly volatile oils Not possible Possible
Oxidation and Hydrolysis (undesirable) Possible Not possible
Similarity of essential oils with the extracted component in terms of Form, Aroma, and Physical Characteristics Less More

Table 2. SCFE Vs Steam Distillation

As a process that holds the United States FDA’s “Green Technology” approval, CO2 SCFE enjoys sizable international clout [1]. One reason for its eco-friendly nature is that it does not generate effluents, automatically eliminating pollution control hassles and costs.

Examined in the context of the limitations of hydrodistillation and solvent extraction, CO2 SCFE delivers a much better performance on all fronts during the extraction of:

  • Plant-based Ingredients: Solvent extraction oxidizes the ingredient that lends color and aroma [8]. Similarly, steam distillation acts strongly and ends up altering the component’s aroma [8]. SCFE acts mildly, thereby avoiding such unwanted changes while also delivering cleaner, fresher, and crispier extracts [9].
  • Herbal Medicines: CO2 SCFE is preferred over hydrodistillation when extracting essential oils because it does not thermally degenerate the oil. It is also replacing solvent extraction for seed oil separation as the solvent cannot be completely disassociated from the seed oil [7].
  • Astaxanthin Extraction from Haematococcus pluviales: CO2 SCFE gives superior results vis-à-vis solvent extraction that employs acetone and hexane. These solvents cannot tell between astaxanthin and the astaxanthin-lipid mixture, both of which occur inside Haematococcus pluviales. As a result, these solvents deliver a low-concentrate extract [10].
  • Beer, Wine, and Blended Alcohol: CO2 SCFE lowers the alcohol content of wine to a bare minimum while leaving its organopletic features undisturbed [11]. The process also extracts the original versions of hop flavors while extending their life [12], thereby acting as a natural preservative for beer.

Organopletic properties of wines are their aroma, fruitiness, crispiness, sweetness, and freshness [13]. Hop is the plant whose flower imparts the prized bitter taste to beer.

  • Phytochemicals: Because supercritical CO2 is naturally non polar, it can better distinguish between volatile, non-polar, and low molecular weight phytochemicals [14].

The selectivity of SCFE is an asset here as it can separate anthocyanin from the pulp of Euterpe oleracea at a certain pressure while extracting phenolic phytochemicals from that very pulp at another pressure [14].

  • Algae:
  • Carotenoids: Hiking the pressure and temperature of the CO2 SCFE process boosts the efficiency of carotenoid extraction. Utilizing the solvent extraction process for the same consumes large quantities of solvent, takes longer, and delivers impure and deficient yields [15].
  • Antioxidants: Employing CO2 SCFE on Haematococcus pluvialis, a microalgae, gives good yields of lutein, astaxanthin, and fatty acids [16].
  • Fatty Acids: CO2 SCFE is able to better differentiate between different fatty acids as compared to pyrolysis / thermal liquefaction and solvent extraction via hexane, the traditional methods for fatty acid extraction. Besides, these conventional techniques are slower [17].
  • Sterols: CO2 SCFE enables solvent-free extraction of phytosterols that are safe for use in the food and beverages industries [18].

The Verdict

People the world over are shifting to natural alternatives – natural medicine, natural food, natural beverages – in realization to the long term side effects that synthetic products, possibly laced with toxic residues, can unleash on health and overall wellbeing.

Effectively this means, the SCFE process and, more specifically, the CO2 SCFE process, are here to stay . . . for ages.


Buffalo Extraction Systems supports the North American & Canandian clientele across a diverse range of extraction systems for a genuinely turnkey experience.

Contact us at info@buffaloextracts.com and get a feel of top of the drawer professionalism.



References

  1. https://automation.cybernetik.com/2019/05/13/why-co2-extraction/
  2. https://www.inno-foodproducts-brainbox.com/2018/05/22/clean-label/
  3. https://en.wikipedia.org/wiki/Supercritical_fluid
  4. https://www.chemengonline.com/supercritical-co2-a-green-solvent/?printmode=1
  5. https://www.sciencedirect.com/topics/immunology-and-microbiology/solvent-extraction
  6. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/organic-solvent
  7. http://www.florajournal.com/archives/2019/vol7issue1/PartA/7-3-34-739.pdf
  8. https://www.mjcce.org.mk/index.php/MJCCE/article/viewFile/35/10
  9. https://www.sciencedirect.com/topics/food-science/supercritical-fluid-extraction
  10. https://www.phasex4scf.com/supercritical-fluids/supercritical-fluids-nutraceuticals
  11. https://core.ac.uk/download/pdf/36063257.pdf
  12. https://www.supercriticalfluids.com/wp-content/uploads/TN-109-Beer-Hop-Extraction1.pdf
  13. https://www.winefrog.com/definition/1001/organoleptic
  14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6152233/
  15. https://www.mdpi.com/1660-3397/14/11/214/pdf
  16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6163853/
  17. https://www.sciencedirect.com/science/article/pii/S1877705812029761
  18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4515614/