Winterization: Filtration and Vacuum

More on Winterization

Now that you’ve pulled your alcoholic vessel of fatty crude soup out of the freezer, you are ready to start de-fatting the solution. Unless you are a fan of watching paint dry, you may want to carefully plan how to tackle the next step. The temptation here will be to pour it all out into your tabletop Büchner funnel on full vac and force it through the smallest pore filter-paper you can buy. Unfortunately, unless you have a sophisticated multi-stage filtration system ready, you are in for a world of frustration, abysmal flow rates, and just an all-around bad time. This is the number one issue most smaller labs fail to scale properly!

Don’t worry we will have a thorough SOP for you in the next article, but we are big proponents of teaching people to fish rather than just giving them the fish. The more you learn about this process the easier it becomes to troubleshoot later if there are any issues. Let’s talk briefly about proper filtration protocol and how to select the correct paper mesh size, filter media, and pressure.

Filter Screen Mesh Sizes and Filtration Media

The first filtration is usually the slowest because it will contain most of the fats. The way to ensure it is a smooth experience is to use a larger pore paper to do an initial “Rough Cut”. We usually recommend a 50-25um filter for fast flowrate. The second filtration can be done at 5-8um/micron at which point you should not have any more coagulated particulate in your solution. Now remember – lipids do coagulate at different concentration levels. Another overnight freezer treatment should be performed followed by another 5-8um/micron filtration to ensure proper winterization.

A great way to keep your filter from clogging is to select a 100-350um porous media and create a filtration cake on top of the paper. This promotes flow rate by protecting the pores of the paper form becoming overwhelmed. When flow rate slows, you can scrape the top layer of the cake to remove accumulated fats and restore filtration speeds. Some media can even promote the removal of more than just large particulate but heavy metals and even pigment compounds via chemisorption and/or electrostatic absorption.

ColumboLabs has a great solution for this initial filtration called RapidFlow. It is a proprietary blend of naturally porous minerals which aids in filtration of during winterization and degumming. Activated adsorbents in the blend help trap triglyceride bodies more effectively than silica or diatomaceous earth on their own. The specially engineered media has a propensity to cling on to fats and gums on a molecular level which promotes the most effective refinement of crude. The media is also a desiccant allowing it to trap excess moisture which may have been picked up by the solvent throughout the winterization process.

Negative (Vacuum) and Positive Pressure

Another aspect to consider is the pressure you apply to the filtration apparatus. The most common type of filter is a vacuum assisted Büchner funnel setup. These come in various sizes and configurations, but all work the same basic way. A vacuum is created which pulls liquid solution through the filter paper trapping the fats on the receiving side while allowing the liquid to flow through the tightly knit pores. A vacuum pump creates the pressure which initiates the flow. There is another method which uses positive pressure and requires a slightly different set-up. In a positive pressure filtration system, an inert gas like oxygen (via air compressor) or N2 is hooked up to a closed-loop vessel which pushes the liquid through the filter instead of pulling it through. In both instances the amount of pressure applied is a big factor in how efficiently the system will run.

When running filtration in a vacuum-assisted system, its important not to apply too deep of a vacuum. What typically happens if you overdo the pressure is the coagulated particles enter deeper into the pore openings of the filtration paper causing a clog. Flow-rate will slow to a crawl and you will need to stop and change out the paper in order to get anything done. This is highly disruptive and time consuming (as well as annoying) and should be avoided. If you have the luxury of a vacuum gauge for your filtration vacuum pump, we typically recommend a range of 300-400 Torr for the initial rough-cut, and slightly deeper (200-300 Torr) for secondary and subsequent filtrations. If using a glass receiving vessel, keep an eye on the flow of the liquid at the discharge – your flow should be even and steady. If the flow starts to spray or spit, you may need to lighten the depth of the vacuum pull (or add more solution to the filter depending on what’s going on up top).

Positive pressure filtration is a mixed bag as there is no one-size-fits-all pressure recommendation. It depends largely on the PSI threshold of the paper you are using. We usually see a range of 25-50 PSI for most equipment although filter-presses could go as high as 100+ PSI. Consult the equipment manufacturer for guidance on proper pressure and flow.

Winterization Loss?

A question we get asked regularly is: “What’s the typical yield loss to fats after winterization?”

This is difficult to answer and depends on several factors; type of crude and post-filtration procedure.

Co2 and BHO crude (primary extraction preformed with a lipophilic solvent) are typically higher in fats than ethanol-extracted crude. We typically see a 10-15% “loss” with these types of crude post-winterization. Ethanol crude quality depends on temperature of the extraction; -46C or colder typically doesn’t extract any fats. Expect a very minimal 3-5% (or less) loss on winterizing etoh crude. We have a whole article devoted to explaining the crude characteristics between different extraction solvents – have a read!

A great method for minimizing cannabinoid loss after filtration:

If you notice that the accumulated fats contain a very yellow pigment, it may be worth rinsing them in some cold ethanol immediately after you finish filtering your main batch of winterizing extract. This is done by pouring a small amount of super-chilled alcohol into the Büchner funnel (enough to fully submerge the fat-cake on top of the filter media/paper) and allowing it to settle into the filter for a few minutes. The cold temperature won’t dissolve the fats but will wash out any residual cannabinoids and terpenes which could still be present in the lipid-mass. You can pull a vacuum to thoroughly dry out the cake. For positive-pressure filtration systems, you may require quite a bit more alcohol to preform a thorough flush through the system – so make sure to keep a few extra gallons in the freezer at all times.

Final Thoughts

Save all your accumulated fats; they can be re-utilized in balms, creams, and salves. Remember – bud trimmings were once considered a useless waste-stream and is now a valuable commodity used to make concentrates. There is no telling what will be possible in the future!

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