02 May How to Remove Dark Color from Ethanol Extracts
The Ethanol Extraction Problem: Chlorophyll, Xanthophyll
One of our potential customers recently asked us how to remove color from their extracts. They were getting dark extracts and were wondering about their options to make them look better. The oil was coming from an ethanol extraction process. As a matter of comparison, the adjacent figure compares an ethanol extract to a CO2 oil extract that has been diluted in ethanol.
The Ethanol Extraction Conundrum
First, there are a couple of points on ethanol extraction. If you extract plant material with warm ethanol, pigments and waxes will be co-extracted. These pigments typically taste bad and give a poor quality appearance to the oil. Rotovaps or stills are typically used to remove the ethanol but the pigments, waxes, and poor quality elements remain in the extract. To reduce the amount of non-active extraction, some people use extremely cold ethanol (<-20 oC) to reduce the waxes and pigments that are extracted; However, just with any other chemical process, as the process gets colder, friction factors increase exponentially and diffusion coefficients of the actives in the ethanol plummet. Thus, the recovery suffers greatly and the absolute amount of active that is extracted greatly decrease. In short: you get to choose: low recovery or high pigments.
Ethanol Is a Flammable Solvent
The other important aspect of ethanol that should be considered is the fact that ethanol is flammable and there are many regulations around storage and use and you should be familiar with these regulations before attempting to build a process based on large amounts of flammable liquid. Even if you are in a rec state, you should consider the infrastructure requirements and permit barriers to using large volumes of ethanol. The National Fire Protection Association has published NFPA 30 guidelines for explosion proof fixtures and infrastructure required. You can also find OSHA regulations here.
Don’t use That Solvent
We have come across an increasing number of uninformed and uneducated ethanol extractors using denatured ethanol or isopropyl alcohol. Uh. Ok. Whatever.
Activated Carbon and Its Drawbacks
We have been approached by many purveyors of ethanol extracts to help them try to remove color. They typically use activated carbon which is quite effective at pigment removal. However, it is also very effective at removal of actives. So the yield suffers greatly. The yield is low for a couple reasons: First, the large pore diameter distribution and particle friability. We wont talk about these here but suffice it to say, there are good scientific reasons for poor recovery when you use activated charcoal.
Another problem with activated carbon is it’s natural origin and the contamination that it carries. Activated carbon is typically derived from coconut shells or bitumen or wood. These products have significant ash content that contain heavy metals. When the carbon breaks up under use, these metals distribute throughout the oil as very small particles. They become very hard if not impossible to remove via filtration. Thus, they end up in your extracts.
The most overlooked aspect of using activated carbon however, is the solvation and dissolution of benzopyrenes into the extract. These class of compounds are a consequence of the combustion of the coconut or bitumen. The wiki on that compound states the following:
Benzopyrenes are harmful because they form carcinogenic and mutagenic metabolites (such as (+)-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide from benzo[a]pyrene) which intercalate into DNA, interfering with transcription. They are considered pollutants and carcinogens.
Why CarbonX is Different
So, care must be taken to use the right carbon. CarbonX has been shown to solve the problems above because it is not a natural product but is engineered by vapor depositing carbon onto a porous substrate. The substrate will not break up so introduction of unfilterable micron sized ash content is not likely. Furthermore, the material is washed so that extractables are not leaching from the materials into the extract.
We typically use CarbonX in a couple different ways:
- You can use CarbonX as a filter cake in conjunction with a DrainDroyd.
2. You can use CarbonX dispersively by pouring it in, mixing, and then waiting for results. Then a DrainDroyd is used to filter the carbonX out of the extract.
We have methods available for download along with MSDS upon purchase. The adjacent figure shows how carbonX will remove colors from ethanol solutions.