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What do Subcritical and Supercritical Refer to?

Extraction Magazine, Media Partners

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The clamor for cannabis concentrates isn’t dying down; dispensary shelves are packed with potent, cannabinoid-rich extracts.

Supercritical carbon dioxide (CO2) extractions are more common, but there are actually two different CO2 extraction methods available to professional laboratories. Subcritical CO2 extractions are possible as well, and each strategy has its own advantages.

Understanding Supercritical CO2 Extraction

CO2 can be tuned through pressure and temperature to act as a solvent and strip valuable terpenes and cannabinoids , along with other active compounds, from cannabis plant material. In the context of extraction, a solvent is “supercritical” if it simultaneously has the properties of both a gas and a liquid.

Supercritical state of CO2 is achieved when CO2 is heated above 31.10°C and exposed to pressures exceeding 1,071 psi. However, it’s worth noting that manufacturers often work with even higher pressure and temperature inputs to optimize their extraction processes. [1]

Supercritical CO2 extraction offers several benefits:

  • Safety: It is generally regarded as a safe method due to its high exposure limits. Safety is paramount when working with solvents, and supercritical CO2 meets rigorous standards.
  • Cost-Effectiveness: This method is relatively cost-effective. High-purity CO2 can be readily sourced from numerous suppliers, ensuring the quality and consistency of the extraction process. This reliability contributes to cost efficiency. Moreover the solvent can be reused in a closed loop system and it is possible to perform various extraction cycles with the same purified solvent.
  • Purity: Supercritical CO2 extraction produces highly pure extracts with minimal residual solvents or contaminants, making it an attractive choice for those seeking pharmaceutical-grade products.

The Subcritical CO2 Extraction Alternative

While supercritical CO2 extraction is widely embraced for its efficiency, subcritical CO2 extraction offers different advantages that cater to a distinct market segment.

In subcritical CO2 extraction, temperatures and pressure below the critical point are used to extract cannabinoids and other cannabis constituents. With these parameters CO2 is in the liquid stage. Even if in this stage the CO2 has less solvent power, this can be beneficial to selectively extract certain compounds.

Involving low temperatures, CO2 at the subcritical state is perfect to obtain cannabis extracts in the real “raw” form, without decarboxylating acidic cannabinoids, harming heat sensitive terpenes and extracting also vitamins and fatty acids.

Terpenes are responsible for the distinctive aromas and flavors of different cannabis strains and are highly sensitive to heat degradation. Subcritical extraction, with its gentle processing conditions, is the preferred method for those who prioritize the taste of their extracts. The terpene-rich end product is in high demand among cannabis connoisseurs.

However, subcritical CO2 extractions yield smaller quantities of oil compared to supercritical methods, so the extracts are more expensive. This is a serious consideration for researchers and product developers who want to isolate specific cannabinoids or terpenes, a  process easily accomplished through subcritical CO2 extractions. It’s possible to create custom formulations and conduct detailed studies on cannabis compounds.

What’s Best for Consumers?

As with many extraction methods, the choice of supercritical or subcritical CO2 extraction ultimately depends on consumer preferences and the producer’s product objectives. Subcritical extractions favor flavor and aroma and the full spectrum composition of the raw cannabis extract, while supercritical extracts offer greater potency in terms of final cannabinoid concentration.

The higher yields of supercritical CO2 extraction also make it a more economical and efficient extraction option for producers.

Future Prospects in Cannabis Concentrate Production

The cannabis concentrate market is growing rapidly, and innovations in extraction technology are helping to drive that growth.

As the industry matures and operators gain more experience with extraction methods, subcritical CO2 extractions may become even more relevant. This technique allows producers to create unique products with customized terpene profiles, which could be just what consumers are looking for.

However, it’s clear that both supercritical and subcritical CO2 extractions have a role to play in the emerging world of cannabis concentrate production. Both techniques cater to different aspects of the market, from efficiency and purity to flavor and aroma preservation.

References:

  1. Sexton, M. et al. “Evaluation of Cannabinoid and Terpenoid Content: Cannabis Flower Compared to Supercritical CO2 Concentrate”, Planta Med, 2018, Volume 84(04): Pages 234-241.

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