1. Technical Overview

Carbon dioxide (CO2) supercritical fluid extraction (SCFE) is the preferred method for segregation of ingredients in the Flavor and Fragrance industry [1]. CO2 SCFE is possible at low pressures and near-room temperature, making it cost-effective. Moreover, CO2 is colorless, odorless, safe i.e. nonflammable and non toxic, and available in pure form. And the fact that CO2 can be sourced from the atmosphere makes CO2 SCFE an eco-friendly process.

Figure 1. Extracted Oil

Solvent extraction, mechanical separation, and distillation are the other three methods utilized for plant flavor concentration [2]. Compared to steam distillation, SCFE acts mildly on plant samples, maintaining the original aroma [3]. Plus, the extracts are cleaner, fresher, and crispier. Hydrodistillation can chemically alter the extracted ingredient while organic solvent extraction tends to modify the ingredient’s color and aroma [4].

2. Global Flavor & Fragrance Market

2.1. Industry Drivers

Rising demand for natural ingredients and greater willingness of the expanding middle class to pay for such products will be the chief factors forecasted to drive the global flavor and fragrance market to $36.6 billion by registering a CAGR of 4.3% between 2019 and 2024 [5].

Makers of natural flavors command higher prices by charging a green premium. Primary drivers of the industry are:

  • Increasing customer taste for products with natural ingredients, which are regarded healthy, safe, and medicinal [6].
  • Expanding disposable incomes of the global middle class.
  • Rising use of biotic elements by the dairy and beverage industry.
  • Transforming customer preferences.
  • Greater utilization of flavors in the dietary supplement, pharmaceutical, and nutraceutical sectors [6].

2.2. Segments & Applications

Rose oil, tuberose absolute, angelica root oil, jasmine absolute, ambrette seed oil, and orange flavor oil are among the most prized in the flavor and fragrance industry [2]. The industry utilizes over 500 natural raw materials sourced from more than 250 species of plants [2].

Broadly, the industry is segmented into [6]:

  • Flavors: Beverages, Bakery, Confectionary, Dairy, and Convenience Foods; and
  • Fragrances: Cosmetics-Toiletries, Soaps-Detergents, and Fine Fragrances.

The industry can also be classified as [6]:

Natural Aroma Chemicals
  • Oleresins
  • Paprika: Piperine etc.
  • Turmeric: Curcumin etc.
  • Black Pepper: Piperine etc.
  • Gingerol
  • Ginger
  • Essential Oils
  • Orange: Myrcene, Limonene
  • Eucalyptus: Limonene, Eucalyptol
  • Lemon: Limonene, Pinene, Camphene
  • Corn Mint: Menthone, Menthol
  • Pepper Mint: Menthone, Menthol
  • Esters
  • Benzyl Acetate
  • Methyl Decanoate
  • Ethyl Acetate
  • Ethyl Benzoate
  • Aldehyde
  • Vanillin
  • Benzaldehyde
  • Alcohol
  • Menthol
  • Lauryl Alcohol
  • Phenol
  • Ethylvanillin

Table 1. Natural and aroma flavors-fragrances

3. Supercritical Fluid Extraction (SCFE) & Carbon dioxide (CO2) SCFE

3.1. Why SCFE Use is Rising?

Regulations on toxicity, quality, safety, and residues in consumer products are getting stricter as consumers demand products with more natural ingredients in food-beverage, pharmaceutical, neutraceutical, and personal care products. SCFE is safer, more eco-friendly, and leaves behind zero or less toxic residues in the final product.

Alternative methods have drawbacks:

  • Solvent Extraction: uses toxic organic solvents whose residue cannot be completely separated from the extracted ingredient [7]. Some solvents deplete the ozone layer and create environmental issues [8].
  • Hydrodistillation: employs heat which can thermally degrade the ingredient [9].

3.2. What are Supercritical Fluids & How do they Assist with Extraction?

A fluid at above its critical pressure and temperature is a supercritical fluid. The phase boundary between its liquid and vapour phase disappears and its properties can be customized by changing the pressure and temperature.

Roughly, supercritical fluids with higher density possess greater solvent power. And because altering pressure and temperature substantially varies their density, supercritical fluids make exceptional solvents.

Figure 2. Triple Point Parameters

Supercritical fluids are excellent solvents because of their [10]:

  • Higher, Liquid-like Density: boosts solvent power.
  • Low, Gas-like Viscosity: improves mass transfer and diffusion inside porous solids.
  • Low, Gas-like Surface Tension: enables greater seepage inside porous solids.

3.3. Why Supercritical Carbon dioxide (CO2) Makes an Excellent SCFE Solvent?

Carbon dioxide and water are the most popularly utilized supercritical fluids [11]. Supercritical (CO2) is an ideal solvent for SCFE because it [10]:

  • Has a critical temperature of 31.10C, which is around the ambient temperature. Relatively low temperatures for CO2 SCFE avoid thermal degradation.
  • 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.
  • 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, reused, and recycled.


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References

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6270407/
  2. https://onlinelibrary.wiley.com/doi/10.1002/9783527693153.ch3
  3. https://www.sciencedirect.com/topics/food-science/supercritical-fluid-extraction
  4. https://www.mjcce.org.mk/index.php/MJCCE/article/viewFile/35/10
  5. https://www.lucintel.com/flavor-and-fragrance-market.aspx
  6. https://www.grandviewresearch.com/industry-analysis/flavors-fragrances-market
  7. https://www.sciencedirect.com/topics/immunology-and-microbiology/solvent-extraction
  8. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/organic-solvent
  9. http://www.florajournal.com/archives/2019/vol7issue1/PartA/7-3-34-739.pdf
  10. https://www.chemengonline.com/supercritical-co2-a-green-solvent/?printmode=1
  11. https://en.wikipedia.org/wiki/Supercritical_fluid