Science of Extraction

THE SCIENCE OF EXTRACTION

How it’s made: extraction and purification methods

MediPharm Labs uses Supercritical CO2 extraction for primary extraction, and short-path wiped-film distillation and centrifugal partition chromatography for further purification and cannabinoid isolation.

Looking at primary extraction techniques, there are three main extraction processes used in North America: Supercritical CO2, hydrocarbon (butane and propane) extraction and alcohol (ethanol) extractions. In the US, hydrocarbon extractions tend to dominate, while sCO2 extraction is the dominant technology in Canada. Each method has advantages and disadvantages that make it suitable for specific types of end products.

Below is a detailed overview of the mechanics of supercritical CO2 and hydrocarbon extractions. In our view, the key take-away is that supercritical CO2 extraction can be customized and is safe. While the investment in technology is higher, we believe it is the appropriate technology for pharma-quality products and an industrial-scale operation like ours.

Milling

MediPharm’s extraction process starts with the milling of dried cannabis through a grinder in an air filtered, temperature and humidity-controlled room. We purchase dry cannabis from multiple cultivators – targeted for quality and specific cannabinoid content. By milling the plant to a fine and consistent particle size we are able to achieve standardization, as well as increase the packing density within the extraction columns, resulting in greater extraction efficiency.

Decarboxylation

This process is known as decarboxylation and can be achieved through heat and (to a lesser extent) time. Starting with dried cannabis, MediPharm “bakes” plant material in an oven [utilizing a prescribed, multi-stage heating profile] to activate the cannabinoids while simultaneously removing moisture and volatile terpenes. MediPharm decarboxylates at lower temperatures to prevent the formation of the degradation product cannabinol (CBN).

Supercritical CO2 Extraction

Supercritical CO2 extraction is well suited for the production of concentrates utilized for Cannabis 2.0 products. It is generally a good choice for safe, high volume cannabinoid production, with the main drawbacks being equipment cost.

Cannabinoids are extracted as outlined below:

  • CO2 extraction uses a closed-loop system, with three primary components: a CO2 accumulator, an extraction vessel and a separator.
  • Liquid CO2 from the accumulator is mixed with plant materials in the extraction vessel. As temperature and pressure rise, the CO2 is in a “supercritical” state, where it takes on the characteristics of both a gas and a liquid.
  • The supercritical state allows the CO2 molecules to pass through solid materials like a gas, while acting as a liquid solvent that can dissolve materials. This combination pulls cannabinoids from plant materials into the CO2
  • The extracted liquid mixture moves to the separator unit where the cannabinoids are separated from the CO2 through a reduction in pressure. The pressure reduction frees the CO2 molecules, which return to a gas state and flow back to the accumulation tank. Simultaneously, the raw cannabis extract is drained from the separator vessel.
  • While the terpenes gets lost in the supercritical extraction process, they can be captured by running subcritical followed by supercritical processes or added back to the finished product during the downstream product formulation step.

Below, we outline a simplified extraction setup.

Source: Golden XTRX. https://www.youtube.com/watch?v=dgfPI0MbLho. Modified

MediPharm Labs’ industrial-scale supercritical CO2 extraction equipment manufactured by Vitalis Extraction Technologies

Winterization

The residual plant extract material, referred to as crude extract, contains a mixture of natural fats, chlorophyll and other impurities which MediPharm Labs strips out to produce a purer cannabinoid extract. During this process, ethanol is added to the crude extract.

From a volume perspective, the crude extract is roughly equal to 15% of the input materials. It generally undergoes a cold-filtration process known as “winterization”, the mixture is cooled in a freezer where the lipids settle at the bottom and the ethanol mixture rises to the top. A simple analogy for this is making soup, where the fats accumulate on the surface and separate from the broth on the bottom.

Rotary Evaporation

Once the fats have been removed, the mixture undergoes a rotary evaporation process that removes any residual ethanol, resulting in a relatively pure cannabis resin (70-85%) product that is very thick and dark in colour, akin to ‘black strap molasses’, and the primary extraction process is complete. This concentrate can be used in tinctures, vapes and other products.

Short-path distillation

MediPharm Labs performs secondary processing, utilizing short-path wiped-film distillation to further refine the cannabis resin. We believe the bulk of commercial processes would conclude at this step, which is considered high quality for the recreational and medical market. Chlorophyll, terpenes, and plant pigments are separated out from the cannabinoids, resulting in a distillate that is more concentrated (>80% purity) and is now golden and clear in colour as well as being virtually odourless. As the finished distillate tends to be very thick – almost solid at room temperature - it is diluted with cannabis-derived or other natural botanically-derived terpenes to reduce viscosity and help it flow through vape cartridges for example. These added terpenes bring unique flavours and aromas to the distillate which had been lost earlier in the processing.