This method also known as fractionate crystallization involves the use of extremely cold temperatures to remove lipids from crude extracts. This technique is used to refine oils from higher melting points fats and waxes. Lipids are fatty acids which can be extracted by certain solvents along with the desired active compounds and once precipitated out the mixture they can be removed through filtration or centrifugation. Removing lipids is important because it helps create a higher purity extract, which means a better product with prolonged shelf-life. 
The amount of fat in the extract being winterized will depend on what extraction technique is used. Cold ethanol is the best method for reducing the amount of fat in the extract.
The removal of plant material can be done through bag filtration. This involves the use of a strong sanitary bag filter which is placed between the extractor and a holding tank.  As the material moves from the extractor to the holding tank, unwanted material will be filtered out through the filter bag. These bags can be emptied every once in a while and used again. Through this technique is possible to obtain a higher quality product and to remove residual plant matter from the extract. Using vacuum filtration is possible to recover higher amount of liquid mixture in shorter times.
Depending on the size of the filter is possible to have different degree of purity of the final extract.
Depth filtration involves loading special cartridges into the lenticular housing that collect unwanted solid particles and separates them from the filtered liquid.
Carbon filtration is generally used to adjuist aroma, flavor, the color of an extract or to remove impurities from it.
Wiped Film Distillation
The main function of this process is to fractionate a mixture and separate compounds depending on their boiling points through the use of heat and vacuum. More volatiles compounds are collected in separate chambers and the residue accumulate at the bottom of the apparatus: depending on the needs is then possible to collect the desired fractions that can be both the volatiles or the residue. Wiped film distillation is very quick with each cycle only taking one to two minutes to complete and the continuos process allows a high efficiency.
Through crystallization is possible to obtain a pure extract removing from the solution unwanted substances or separate the desired compounds in the form of crystals. In this technique a solid phase is separated from the mother liquor. By dissolving impure solids in a minimal amount of hot solvent and slowly cooling down the mixture, pure crystals will be formed precipiting out from the solution and the impurities will remain in the mother liquor. Depending on the compound solubility in a chosen solvent is possible to fractionate the mixture and succesfully purify an extract.
- Winterization of cannabis oil extracts to remove fats and waxes. B/R Instrument Blog. (2018) https://brinstrument.com/blog/cannabis-distillation/winterization-of-cannabis-oil-extracts-to-remove-fats-and-waxes/
- Scott Labs | A Guide to Botanicals Filtration. Scott Labs. 2022. https://scottlab.com/botanicals-filtration-guide