The importance of obtaining a pure cannabis extract continues to grow. Production companies are making sure their final extracts are free of undesirable components such as waxes, lipids, and fats. Many are achieving this through a process known as winterization. After extraction, winterization is a final step that can be taken to reach a further purification of extract.
Winterization, also known as dewaxing, is a vital step to creating a high-purity extract in the cannabis industry. Winterization is the removal of the unwanted substances including, waxes, lipids, and fats of the plants in the crude extract. It is important to winterize to remove fats because the fats dilute the final concentration of cannabinoids in the final extract which lowers the purity and then affects the overall value. These fats can cause the final extract to be cloudy and less attractive, also resulting in a lower value. Removing the fats and waxes will result in a pure sample, stable viscosity, and a longer shelf life.
Depending on the method of extraction, it could vary the amount of fats that can be removed during the winterization process. A cold ethanol extraction is the best extraction method for minimizing fats in the extract. The CO2 extraction method is usually the method that contains the most amount of fats in the final crude extract. The methods to complete winterization include four steps: dissolve, cool, filter, and boil.
Dissolve the extract in 30 to 60°C of ethanol using a 10 mL:1g (ethanol:extract) ratio. 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.
Once this is complete, a vacuum filtration system is the final step using a vacuum pump, Buchner funnel, and filter paper. 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.
Solvent at warmer temperatures, completely dissolves the sample. Cooling the solvent, the solubility is decreased, and the waxes are precipitated out.
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