Why is Post Extraction Processing Necessary?

Hemp oil obtained after subjecting hemp to Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) is further processed to obtain products with the desired chemical composition.

Also called refining, post extraction processing of hemp oil includes winterization, de-carboxylation, and distillation [1]. Chromatography serves as a substitute to distillation, particularly when isolating heat-sensitive molecules [2].

 

Post extraction hemp processing is geared towards maximizing the cannabidiol (CBD) content in the end product. Another objective is to maintain some amount of terpenes and flavonoids. Many processors also eliminate tetra-hydro-cannabinol (THC) from the extract to avoid legal hassles.

Cannabis contains a number of cannabinoids including CBD and THC. Now, THC is psychoactive, CBD is not [3]. Simply speaking THC intoxicates or gets the user “high,” CBD does not. Rather, CBD delivers multiple health benefits. Terpenes lend a distinctive aroma to the product while flavonoids impart it a specific flavor [4].

Hemp is cannabis with 0.3% or less dry weight of THC. Cannabis with over 0.3% THC by dry weight is marijuana [3]. While hemp is legal in many parts of the world, marijuana is not [5]. For many, this difference is not clear and introduces unnecessary confusion during the licensing, transport, and use of hemp and its products.

Legal differences are another source of inconsistency. Some states mandate zero THC content in hemp products [6]. Authorities of such states can deny product license. Or hold up the products at the state border. To avoid legal hassles, some manufacturers choose to eliminate THC altogether from their hemp products [1] via THC remediation.

 

Post Extraction Processing of Hemp Oil

Starting with winterization, which eliminates waxes, lipids, and fats, post extraction processing moves to decarboxylation and distillation. Decarboxylation makes cannabinoids available in their free form for active interaction with the nervous system – this interplay facilitates their benevolent health impacts.

Distillation selectively separates other ingredients to maximize CBD concentration. Chromatography often acts as an option to distillation.

 

Winterization is the first procedure and mainly removes waxes from the hemp oil [7]. It also eliminates fats and lipids [8]. These impurities make the oil distasteful, dark, and cloudy [9]. The process involves:

  • Mixing crude hemp oil with ethanol and stirring the mixture strongly. This dissolves the desired components of crude oil into ethanol while separating out the undesired elements [7].
  • Freezing the mixture coagulates the un-required elements out which settle at the bottom of the solution [4].
  • Filtering separates the waxes, fats, and lipids. Equipment for filtration includes filter paper, Buchner funnels, and filter presses. Vacuum on the downstream side makes Buchner funnels faster than gravity filters [10]. Pressurized filtration action makes filter presses quicker than Buchner funnels [11].

Top producers employ multiple freezing and filtering passes.

  • Rotary evaporators (rotovaps) vaporize the ethanol from the filtrate leaving behind winterized hemp oil. The system operates under vacuum wherein a bulb containing the filtrate rotates inside hot water [9].

Vacuum lowers ethanol’s boiling point and helps retain the more thermally-sensitive elements in cannabis oil. As ethanol evaporates, winterized CBD oil is left behind. Condensers recover the ethanol and re-use it [9].

 

Decarboxylation converts cannabidiolic acid (CBDA) into CBD and tetrahydrocannabiolic acid (THCA) into THC. The acids are inactive but CBD and THC are active [12]. CBD is of course the main required ingredient.

Heating the winterized oil and holding it at a specific temperature for a particular duration decarboxylates it i.e. eliminates the carboxyl group from its molecules [12].

 

Distillation makes use of the difference in boiling points of the distinct hemp constituents to isolate them. Consider the boiling points of the elements at one atmosphere pressure [4]:

  • CBD: 1600C (3200F) to 1800C (3560F)
  • THC: 1570C (3150F)
  • Flavonoids: 1340C (2730F) to 1780C (3520F)
  • Terpenes: 1190C (2640F) to 1570C (3150F)

Required processing rate and scale of production determine the distillation process used:

  • Thin Film Distillation: Uses a combination of vacuum (1 mbar pressure) [13] and thin film (under 1 mm) [14] of the solution. Vacuum lowers the boiling point of the components while the thin film facilities rapid evaporation in the shortest resident time [15]. Both prevent thermal degradation of heat-sensitive components.

A rotating wiper applies a very thin film of the decarboxylated hemp oil on the heated inner side of a pipe that acts as the evaporative surface [15]. The component boils and its vapors re-convert to liquid in a condenser located outside the evaporator [13].

  • Short Path Distillation: Is another vacuum distillation technique and is similar to thin film distillation. Except, the condenser is located inside the evaporator body and that it operates at pressures as low as 0.001 mbar [13].
  • Continuous Distillation: Is an uninterrupted process for mass production [16].

 

Chromatography is an alternative to fractional distillation. One advantage of chromatography is it does not utilize heat for separation. Hemp extract is first dissolved in a fluid (mobile phase) and passed through a media (stationary phase). The difference in speed of passage of the diverse hemp components in the media enables isolation [2].

Popular chromatography techniques employed in post-extraction processing of hemp include:

  • Supercritical Carbon dioxide (sCO2) Chromatography utilizes sCO2 as the mobile phase [17]. Does not employ pentane or hexane, which are toxic solvents [18].
  • Flash Chromatography is air pressure powered for rapid separation and is a blend of shorter column and medium pressure chromatography. It does use pentane though [19].
  • High-Pressure Liquid Chromatography (HPLC) pumps the mobile phase at high pressure via carrier gases such as nitrogen or helium [20]. It too utilizes pentane [19].
  • Rotary Counter Current Chromatography (CCC) employs a liquid mix as solvent [18] and a liquid stationary phase [21].

 

Centrifugal Partition Chromatography (CPC) used liquids for stationary and mobile phases. Both phases mix and rotate, with centrifugal force separating and decanting the heavier mobile phase from the lighter stationary phase [22].

 

Full Spectrum, Broad Spectrum, & Other Types of Hemp Oils

Refined hemp oils are also called CBD Distillates. Based on the degree to which they are refined, hemp oils can be:

  • Full Spectrum CBD: These are the least refined of all hemp oils. CBD is their most prominent ingredient and they contain greater percentages of aromatic terpenes, other cannabinoids, and impurities [1].

But because they may also contain tiny fractions of THC, they are exposed to the mentioned issues with transport, licensing, and use. Besides, impurities make them unpleasant as edibles [1].

And yet, people demand them because of the “entourage effect,” the combined, more benevolent effect of multiple cannabinoids [1].

  • Broad Spectrum CBD: Also called THC-free distillate, these are more refined than full spectrum CBD. They do not exhibit the entourage effect and are, therefore, less potent. However, they are a reliable way of staying out of legal complications. Users prefer them as a CBD source without impurities and THC [1].

Manufacturers produce broad spectrum CBD in two ways. First, by refining full spectrum CBD till it is devoid of THC. Second, by adding terpenes and benevolent i.e. non-psychoactive cannabinoids to CBD isolates, the most refined of all hemp oils as described below [1].

THC remediation removes up to 99.9% THC. Crashing the hemp extract i.e. crystallizing CBD out leaves behind THC-rich mother liquor. Chromatography of this liquor isolates THC. The close boiling points of THC and CBD mean separating them via distillation is a tough task [23].

  • CBD Distillates: Contain between 80% and 90% CBD in addition to terpenes and beneficial cannabinoids. High CBD content makes them potent and users have to consume only small amounts to feel the effects. With zero impurities and a honey-like consistency, they do not have any taste or odor [1].
  • CBD Isolates: Are the purest hemp oil variant with CDM content approaching 100%. Produced after multiple refining stages, they too are odorless and tasteless [1].

 

Finally

Exhaustive post extraction processing transports hemp products to a completely different level, into a class of their own! It is no surprise that the global market for hemp products is on an expansion spree.

 

Cybernetik Technologies (CTPL) works closely with trusted partners and has delivered turnkey solutions in Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) for over a decade.

Buffalo Extraction Systems (BES) is our sister concern, supporting Cybernetik’s built-to-order CO2 extraction systems in the United States.

Contact CTPL at +91 20 6790 9600 or [email protected] and experience the fine art of selective extraction.

Write to BES at [email protected] for state-of-the-art CO2 extraction technology.

 


 

References

  1. https://industrialhempfarms.com/what-is-cbd-distillate/
  2. https://bigskybotanicals.com/blog/chromatography-and-the-cbd-industry/
  3. https://medium.com/cbd-origin/hemp-vs-marijuana-the-difference-explained-a837c51aa8f7
  4. https://capnasystems.com/blog/cannabis-distillate/
  5. https://blog.tryplainjane.com/legal-status-of-cbd-around-the-world/
  6. https://www.cannabistech.com/articles/technologies-for-thc-remediation/
  7. https://extraktlab.com/now-that-i-have-extracts-what-are-my-options-to-refine-the-extracts/
  8. https://www.apekssupercritical.com/cbd-extraction-process/
  9. https://www.extractlabs.com/cbd-industry/what-is-winterization/#:~:text=Winterization%20is%20a%20process%20that,and%20have%20an%20unpleasant%20taste.
  10. https://en.wikipedia.org/wiki/B%C3%BCchner_funnel
  11. https://metchem.com/cbd-oil-extraction-filtration-filter-press/#:~:text=Winterization%20%26%20Filtration%20of%20C02%20Extract%20of%20CBD%20Oil&text=A%20filter%20press%20will%20provide,blinding%20on%20the%20filter%20cloths.
  12. https://www.maratek.com/blog/cbd-oil-extraction-what-is-decarboxylation
  13. http://www.avta-us.com/basics.html
  14. https://helderpad.files.wordpress.com/2016/06/the-molecular-separation-of-hemp-oil-4.pdf
  15. https://www.dedietrich.com/en/solutions-and-products/distillation/thin-film-evaporator
  16. https://en.citizendium.org/wiki/continuous_distillation#:~:text=Continuous%20distillation%20is%20an%20ongoing,components%20out%20of%20the%20mixture.
  17. https://en.wikipedia.org/wiki/Supercritical_fluid_chromatography#:~:text=Supercritical%20fluid%20chromatography%20(SFC)%20is,dioxide%20as%20the%20mobile%20phase.
  18. https://lakelandhemp.com/how-to-make-cbd-isolate/
  19. https://ijpsr.com/bft-article/brief-review-on-flash-chromatography/?view=fulltext
  20. http://hiq.linde-gas.com/en/analytical_methods/liquid_chromatography/high_performance_liquid_chromatography.html
  21. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/countercurrent-chromatography
  22. http://www.kromaton.com/en/the-cpc/technologies#:~:text=This%20refers%20to%20the%20rotary,movement%20around%20two%20rotating%20axes.
  23. https://capnasystems.com/blog/thc-remediation/

 

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