1. Technical Overview

Carbon dioxide (CO2) supercritical fluid extraction (SCFE) is increasingly preferred for spice extraction as the process maintains the purity of the separated ingredient. SCFE and solvent extraction are the two main methods utilized for oleoresin extraction. Relatively low temperatures involved in CO2 SCFE make it compatible for extraction of oleoresins, which are vulnerable to heat, light, and oxidation [1].

Figure 1. Spice extracts
Image Credits: Steve Buissinne from Pixabay

Techniques employed to extract essential oils are [2]:

  • Carbon dioxide Supercritical Fluid Extraction (CO2 SCFE)
  • Hydrodistillation
  • Solvent Extraction
  • Cold Press Extraction
  • Maceration
  • Resin Tapping

Hydrodistillation utilizes steam or water for ingredient extraction. Thermal degeneration and hydrolysis processes occur during hydrodistillation and alter the ingredient’s composition [3]. Solvent extraction similarly modifies the ingredient’s composition as the solvent cannot be completely separated from the ingredient [3].

2. Worldwide Spice and Herb Extract Market

2.1. Market Drivers

Spices and herbs are a prized commodity! The global spice and herb extract market stood at $6.91 billion in 2019 and is poised to record a 6.5% CAGR between 2020 and 2027 and reach $9.7 billion [4].

Industry drivers include [5]:

  • Customer demand shifting towards products with natural ingredients.
  • Increased availability of international cuisine in major world economies.
  • Greater consumer preference for organic flavors.
  • Surging requirement for convenience foods.
  • Rising awareness on the health benefits of Ayurveda.

2.2. Essential Oils

Essential oils are extracted from plant leaves, barks, and herbs [6]. Their peculiar flavor finds application in the food-beverage, aromatherapy, cosmetics, fragrance, and home care-cleaning industries. Across the world, people are waking up to the immense health benefits of natural oils. Then again, lifestyle changes have deepened people’s interest in procedures such as aromatherapy.

Applications of essential oils include:

  • Sandalwood: soothes nerves, boosts focus.
  • Orange: promotes digestion, muscle relaxation, and pain relief.
  • Eucalyptus: relieves asthma, head lice, and plaque.
  • Rose: lowers anxiety.
  • Lemon: betters digestion and mood, relieves headaches.
  • Jasmine: assists during childbirth, fights depression.
  • Clove: relief from pain and stomach upsets.
  • Bergamot: relief from stress, eczema.
  • Cornmint: treats colds, headaches, and sore throats.
  • Peppermint: helps digestion, improves energy levels.
  • Chamomile: relaxing effect.
  • Rosemary: triggers hair growth, lowers pain.
  • Citronella: removes parasites and worms from body.
  • Spearmint: employed in aromatherapy to reduce fatigue.
  • Tea Tree: immunity booster, fights infections.
  • Geranium: makes skin radiant, treats anxiety and acne.
  • Lavender: stress relief.
  • Ylang-Ylang: treats nausea, headaches, skin ailments.

2.3. Oleoresins

Oleoresins are the blend of oil and resin, available naturally in plants [7]. They find application in the food-beverage, personal care, pharmaceutical and netraceutical, and feed industries. Drivers of the oleoresin industry are their health benefits and availability in a storage-and-transport-friendly concentrated form [8].

Sources of oleoresins:

  • Paprika
  • Turmeric
  • Herbs
  • Ginger
  • Capsicum
  • Cinnamon & Cassia
  • Seed Spices

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, nutraceutical, 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 [9]. Some solvents deplete the ozone layer and create environmental issues [10].
  • Hydrodistillation: employs heat which can thermally degrade the ingredient [11].

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 [12]:

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

  • 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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  1. Extraction of Oleoresin by Supercritical Fluid Extraction, Capsulation and its Physiochemical Properties. Effat Seliem. International Journal of Current Research and Academic Review.
  2. Essential Oils Market. Markets and Markets.
  3. Supercritical Fluid Extraction: A New Technology to Herbals. Vaibhav Shinde et al. International Journal of Herbal Medicine.
  4. Spices Market Size Worth $9.7 Billion by 2027. PR Newswire.
  5. Herb and Spices Extract Market: Global Industry Analysis, Size, Sales and Forecast by 2027. Mindaspire Market Research.
  6. Essential Oil Market Size. Global Market Insights.
  7. What are Oleoresins? Organic Spices Inc.
  8. Oleoresins Market. Markets and Markets.
  9. Fires and Explosions. Max Houck et al. Fundamentals of Forensic Science (Third Edition). Science Direct.
  10. Initial Considerations. Francisco Pena-Pereira et al. The Applications of Green Solvents in Separation Process. Science Direct.
  11. Supercritical Fluid Extraction. E. Reverchon. Encyclopedia of Food Sciences and Nutrition (Second Edition). Science Direct.
  12. Supercritical CO2: A Green Solvent. Chemical Engineering.
  13. Supercritical Fluids. LibreTexts.