1. Technical Overview

Carbon dioxide supercritical fluid extraction (CO2 SCFE) is a highly favored process in the beer and blended alcohol industries for extraction of hops and other flavours, in order to ensure consistency of product and optimize the use of raw material.

Figure 1. Rising consumption of beer & alcohol
Image credits: Leeroy Agency at Pixabay

Beer industry employs a two-step CO2 SCFE to obtain the essential / aromatic oils in highly concentrated form. It is these oils that lend the valued flavor to the brew. And since the CO2 SCFE process occurs at near room temperature, there is minimal distortion of the flavor, if at all [3].

Moreover, the process maintains the integrity of the hop flavor for a longer duration [3], thereby serving as a preservative. Hop is the plant whose flowers impart the required bitter flavor to beer [4].

2. Beer & Blended Alcohol Markets

2.1. Beer Market

Revenues of the alcoholic beverage market are estimated at $1,587 billion in 2020 [5]. The market includes the beer, wine, perry and rice wine, spirits, and cider segments with beer being the largest by value. The global beer market will be worth $805 billion by end-2024 [6].

Prospects for the global beer industry are bright on account of these drivers [6]:

  • Growing popularity of low alcohol by volume (ABV) spurring sales of low-alcohol and no-alcohol beer.
  • Fast paced urbanization and growing western cultural influences on people, and particularly youth across the world.
  • Higher disposable incomes of youth.
  • Falling prices of low-alcohol beer.
  • Introduction of flavored beers.

2.2. Alcohol Market

The following trends in the market will propel forward the alcohol market [7]:

  • Expanding demand for premium alcoholic beverages particularly among wealthy millennials.
  • Economic growth and rise in disposable incomes.
  • Innovation in products in response to shifting customer tastes viz. high quality and low calorie ingredients.
  • Producers improving distribution and purchase channels via convenience and online stores.

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 [8]. Some solvents deplete the ozone layer and create environmental issues [9].
  • Hydrodistillation: employs heat which can thermally degrade the ingredient [10].

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 [11]:

  • 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 [12]. Supercritical (CO2) is an ideal solvent for SCFE because it [11]:

  • 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. http://www.supercriticalfluids.com/wp-content/uploads/TN-109-Beer-Hop-Extraction1.pdf 
  2. http://allaboutbeer.com/learn/beer/hops/
  3. https://www.statista.com/outlook/10000000/100/alcoholic-drinks/worldwide#market-revenue
  4. https://www.researchandmarkets.com/reports/4536278/beer-market-growth-trends-and-forecast-2020
  5. https://www.mordorintelligence.com/industry-reports/alcoholic-beverage-market
  6. https://www.sciencedirect.com/topics/immunology-and-microbiology/solvent-extraction
  7. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/organic-solvent
  8. http://www.florajournal.com/archives/2019/vol7issue1/PartA/7-3-34-739.pdf
  9. https://www.chemengonline.com/supercritical-co2-a-green-solvent/?printmode=1
  10. https://en.wikipedia.org/wiki/Supercritical_fluid