Winterization is a key step in the chain of cannabis processing, also known as de-waxing, put simply, it’s a form of purification that helps eliminate unwanted lipids, fatty acids, wax, and other inactive compounds impurities in the crude cannabis oil extract. Those compounds contribute a poor flavor, and aroma and lower the percentage of THC/CBD in the final product, and can also cause potential health risks from ingesting them.
When producing cannabis extract that targets the recreational markets, wax, shatter, distillate, or any number of related end products – winterization is a key process that helps improve the overall quality of the product.
Why winterize to remove lipids?
- Fats dilute the cannabinoid fraction, lowering the purity
- Fats can cause distillate to be less transparent hurting its value.
- In vape pens, they can burn on the coil and cause the pen to taste burnt.
Four Steps of CO2 Oil Winterization
The winterization process can be performed in a few different ways but what each has in common is the use of cold temperatures-exposure to colder temperatures to facilitate the precipitation of the undesired compounds, the resulting solids are then removed via filtration.
The winterization process starts with raw extract straight from the CO2 extraction machine. This CBD crude oil contains all the essential parts of the hemp plant except for the actual plant material itself. CBD, minor cannabinoids, terpenes, fats, waxes, and lipids are all part of this viscous liquid. Crude oil extracted from a supercritical CO2 extraction machine will have an attractive, light color to it, especially compared to alcohol-extracted oil, which will have a dark, sludge-like appearance.
Dissolve the CO2 extract in 30 to 60°C of ethanol using a 10 mL:1g (ethanol: extract) ratio, although this will depend on the extraction method. Carbon dioxide (C02) extraction uses much higher pressures than say, butane, and so more of the contained fats, lipids, and waxes will be present. This allows for the complete dissolution of the trichomes, while also making sure that there is enough solvent available to cause the impurities to solidify and separate from the desired components.
Stirring the solution using a lab spatula or using a magnetic heater/stirrer with a stir bar will do the trick. Now the extract is suspended in ethanol. The waxes, lipids, and fats have now been dissolved in the solution. Solvent at warmer temperatures completely dissolves the sample. Cooling the solvent, the solubility is decreased, and the waxes are precipitated out. These fats have a lower solubility in cold ethanol compared to warm ethanol, which is why the next step is to freeze the solution.
Using a chiller/freezer, get the solution as cold as possible. Waiting at least 24 hours should enough time for the waxes to precipitate out of the solution. You will notice a layer of fats have formed on top of the ethanol solution.
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Once the solution has been frozen for the required time frame, it is then filtered through a centrifuge, Buchner Funnel or a filter press. The highest surface area filter paper will allow you to filter out as much precipitate as possible. Keeping the funnel and filter papers as cold as the solution will keep the fats from going back into solution after coming into contact with the warmer surfaces. Using separate filters may help with the filtration, as higher micron sized filters will take out most of the fats but using smaller micron filters will filter the smallest particles of fats. Once the filtration apparatus is set up, use a cold pure ethanol to pre-wet the filter paper and apply a vacuum. Then slowly pour the solution onto the filter paper. A build up of fats will block the ability of the filter paper to continue to pull the solution through.
There are now two separate products: the fats, which will look like a brownish butter on top of the filter papers, and a golden translucent oil. This final step is to evaporate off the ethanol from the oil. Ethanol will boil off at 78.5°C atmospheric pressure. Using a hotplate, boil off the ethanol until the solution reaches a thicker viscosity, close to the viscosity of honey. If using a vacuum oven and are pulling -28.5” Hg, this will reduce the boiling point of ethanol to 12.8°C. This process will purify the cannabis solution creating a higher value of the oil with the least amount of impurities.