Winterization is the process of removing fats and lipids from a solution using temperature and solubility principles of different solvents. My personal favorite for winterization is methanol as the fats and lipids we are trying to remove are least soluble in methanol. All solvent should be reagent/lab grade.
Celite or Diatomaceous Earth
WARNING: Methanol is extremely toxic. Use explosion proof ventilation to pull away all vapors.
STEP 1: ETHANOL BATH
To start, you need to take your oil and create a solution with ethanol or methanol at a 10:1 ratio by volume. Ensure that you are using at least 95% ethanol or methanol*. Once the oil has been immersed in the solution, carefully heat your mixture to 43°C (110°F) to 49°C (120°F). Sufficiently heat the mixture until the concentrate has completely dissolved and/or until bubbling has halted.
*With methanol, you will likely see fats and lipids coagulate out at room temperature or even while the solvent is still warm.
STEP 2: PRIMARY FILTRATION
If you see any lipids coagulate once your resin is completely dissolved immediately filter it with a buchner funnel. If no coagulation occurs, skip to Step 3.
Using a buchner funnel, insert your filter paper and filter ring, then insert into the funnel a 1/2 in layer of Celite or Diatomaceous Earth (DE). With the filtration layer added, run your solution through the funnel.
STEP 3: PRIMARY FREEZE
With the lipids filtered, place your solution into a freezer set at approximately -5°C (23°F).
Leave in the freezer for 24 hours.
STEP 4: SECONDARY FILTRATION
Once the solution has been subjected to freezing temperatures for at least 24 hours, filter through a buchner funnel with Celite or DE as defined during Step 2: Primary Filtration.
STEP 5: DEEP FREEZE
Place filtered solution into a deep freezer set at at least -30°C (-22°C). Leave solution in the deep freezer for at least 24 hours.
Put solution container in a bed of dry ice to help get the temperature as low as possible.
STEP 6: TERTIARY FILTRATION
Filter the solution a third time through a buchner funnel. During filtration, ensure you add as much solution as can pass through the filter in five minutes or less while keeping the rest of the solution in the freezer/dry ice bed.
Following these steps will minimize heat transfer.
STEP 7: SOLVENT RECOVERY/ETHANOL PURGE
Recover and remove all solvent and you now have winterized oil. If using methanol you will need to short-path distill the oil, or give it a very long warm bath in a rotary evaporator at the deepest vacuum you can achieve. Any methanol left in your oil is toxic if inhaled or consumed.