Citric Acid Degumming Tek


#1

Workers use citric acid to “degum” distillate or crude resin intended for making distillate. There are several ways to employ it, and all require a bit of water to disassociate the acid… i.e. make it acidic by letting it ionize into H+ (actually H3O+ “hydronium” cations in water) and negatively charged citric (citrate) conjugate base anions.

Before you begin working with any acid or base, you should measure the starting pH of your hydrated (water-containing) resin solution. To do this, use Hydrion pH paper (the thin roll of yellow paper sold packed in foil in a clear plastic “tape” dispenser with a pH 1.0 to 14.0 color key on it) to test the pH of your room temperature 190 proof ethanol:cannabinoid solution. Write down the starting pH!

In all likelihood, it will be somewhat acidic, but close to neutral. This is mainly due to a natural property of ethanol; it reads slightly acidic because of the strong hydrogen bonding with water. Depending on the resin/distillate content (decarbed or not, terpenols, etc.) and concentration, the pH of the ethanol:resin solution may read between 5 and 7.

The easiest way to use citric to degum is to dissolve the distillate or crude into 190 proof ethanol (95% ethanol with 5% water in an “azeotrope”), the same as is done for Winterization, then dissolve some citric acid into it, little by little with stirring at 25 to 30°C. You do not need or want any excess water in this mixture! The amount of citric acid used is small; since it is acting as a catalyst, it does not get used up, but keeps regenerating after each reaction (rxn) to break apart the phospholipids (aka: gums, phosphatides, lecithin triglycerides).

However, especially in crude, some of the citric does get used up in a complexation (aka chelation) rxn with metal atoms and/or the phosphorous compounds, so you can add small amounts of the solid citric acid to the liquid with stirring, waiting each time for it to dissolve/disappear, just until it stops dissolving, leaving a small amount of solid citric acid in the bottom of the mixing vessel or swirling about as you stir it.

In especially gummy material, you will likely see precipitating veg oil flocculant solid “clouds or puffs” swirling in the liquid… they come from the rxn of citric acid with the phosphatide triglyceride gum, as the triglycerides break apart into separate fatty acid and glycolated phospholipid chains. This just means the rxn is working, and that you have a visibly large amount of gum to react with. Do not confuse these with the solid citric acid crystals (xtals). They look like fluffy clouds, while the citric xtals look like grains of sand. You are done adding citric acid when you either see solid citric acid xtals that refuse to dissolve or if you see no more of the flocculant precipitate forming.

Caveat & Caution: If you are trying to retain all CBD or working with high CBD crude or distillate (like from hemp), it is best to avoid the combination of acid and heat (even just above 30°C) at all times. Otherwise you may end up isomerizing your CBD to Δ8-THC.

If there is visible solid flocculant in the room temperature liquid, go ahead and filter it out, now, using vacuum or pressure filtration as you would for Winterization. It is extremely fine sediment, so it really helps to use a 3-dimensional matrix of filter media over your standard 2D filter paper. This can be a cake of filter aid, like fine laboratory grade silica (e.g. 220 mesh sand) or calcined diatomaceous earth, such as Celite brand (make sure it is documented to have a neutral pH in water… or see below for this special case). You can also use glass wool or (my favorite) pure cotton.

The next, often mistakenly skipped, step is to fully precipitate the flocculant by chilling. This is done exactly the same way you would perform Winterization. After all, you just turned the gums mostly into the very same sort of vegetable oil you would normally Winterize to remove. Chill and filter in small aliquots (parts of the whole liquid body… in order to keep it all as cold as possible or practical during filtration) the same way you filtered above, using filter aid.

Now it is time to remove or neutralize the citric acid. Normally, I recommend a liquid/liquid partition extraction of the cannabinoids from the ethanol by adding excess water to louche (i.e. a milky microemulsion) the resin from the ethanol, then extracting the resin with a layer of n-alkane (hydrocarbon) like n-pentane, n-heptane, etc. Separate the now resin-laden alkane from the now depleted aqueous ethanol, and wash the alkane with some salty water. However, this is not always an option for my clients, nor is it always necessary or desirable, and I would like to introduce a new method…

This is speculation, as I have not tried it yet, but I am a pretty darn good “guesser”. :wink: I am fairly certain we can neutralize and possibly even sequester (lock down) the citric acid by using an alkaline Celite for filter media, but I do not know what makes them all alkaline; there are many types, so the salt products are unknown to me. If you want to use one, talk to Sambo Creeck (sic) Filtration @SamboCreeck.com about Celite filter aid options that are alkalinized with magnesium.

However, I have an idea that plays well with stuff we already use: We should be able to simultaneously neutralize, sequester, and filter out any cold-ethanol-insoluble-but-still-mobile magnesium citrate salt particles by simply adding a layer of the less expensive varieties of magnesium silicate on top of your filter aid of choice from before. Magnesium silicate, aka: MagSil, is now a very commonly available chromatography stationary phase medium known as MagSil PR for pesticide remediation in the cannabis industry… just ask @Shadownaught …but you don’t need the specially calcined PR type for this, so you may be able to get some less expensive back stock of non-PR magsil.

The best part about this is the magnesium citrate salt, even if some slips through the cold filtration, is already alkaline, not acidic, and has a high decomposition temperature of 200°C… and although that is certainly in the range of our distillation process, the decomposition products are magnesium carbonate and eventually magnesium oxide. I should also note that magnesium citrate is a complex salt that has a few different formulae, but most important, I believe, is that they are all hydrates… they require waters of hydration to exist (e.g. magnesium citrate • nonahydrate), so their formation will naturally attract and strongly bond to several water molecules, very likely drying your solution of any excess water, and possibly even breaking the ethanol:water azeotrope! Ionic complexation and requiring waters of hydration also makes the salt more likely to become part of the magnesium silicate, locking it down as a solid.
This all means that no matter what actually happens, the products of this procedure are not going to hurt and may even help your cannabinoid distillation and/or ethanol recovery process(es)! :grinning:

Finally, use the Hydrion paper to test the pH of your degummed ethanol:cannabinoid solution. The pH should be the same as it was when you started, when the paper warms to room temperature after about 1 minute… unless some magnesium citrate salt made it through, which will make it more alkaline… hopefully a nice neutral 7.
However, just in case it is more acidic (i.e. ONLY if it has lower pH than it started with), let the liquid warm to room temperature in a covered vessel (to keep out water condensation from the air), then fully stir in small pinches of magnesium oxide (MgO) at a time to bring the pH to 7.

For the record, this is the first and only time I have ever recommended any pH adjustment outside of pesticide remediation… and I am really just hoping to neutralize the citric degumming acid. I am not shooting for acid or alkaline conditions at all.


Degumming with constraints
#2

thank you @Photon_noir! this is helpful to me. I just got my separatory funnel in and i have a batch of 500g of 1st pass distillate to put through it (probably 70% THC). I’ve been looking for the best technique. some people are saying they alter the Ph of their saline solution when doing the brine wash. can you comment on this?

thanks,

GH


#3

Excellent write up Photon, clears up several minor details of degumming methodology I was unclear about.

Just yesterday I came up with using alkaline bentonite for the same purpose as the alkaline celite in this tek…

I will give it a go in the next couple of weeks, thanks!.


#4

What is your goal? If it is pesticide remediation and you are using distillate that still contains a lot of terpenes, it may not work. I ask because the only time I ever see it recommended to adjust the pH of your brine solution in liquid/liquid partition extractions is when mitigating pesticides. Even then, I do not think it is always necessary.


#5

Cool! Yeah, using a clay for neutralizing may work in the same way. However, be careful with clay powder, since it will tend to become a mud that is very difficult to filter, especially since you are neutralizing citric acid, which tends to make hydrated salts. Instead of making a filter bed with clay, it may be most facile to mix the clay powder with your solution, as if it were a reagent base, then let it settle and decant the liquid over your filter.


#6

This is a key reason to use fast filtering clay like our T5. It works fantastic as a filter aid. @Photon_noir


#7

There ya go, @puccinia ! @Shadownaught , does the T5 have alkaline properties?


#8

So in my case i have a around 100lbs of pretty bad outdoor trim. no pesticides though, just crappy material in general. Our bho extraction is only yielding 8-9% and the bho is roughly 65%-68% THCa. the bho has a lot of green tint to it, so i was hoping to use the separatory funnel to clean the material before the final distillation to achieve higher potency.

Currently two passes is only getting me to 75% THC. meanwhile when i start with nug run i’ll hit 85-88% in two passes. I’m looking to master the sep funnel/winterizing moves to get a clean starting product no matter what the input material.


#9

We have filtration aides (DE Celite) of high PH specifically for this type of application.


#10

Hmm… sounds like a testing issue combined with poor quality material, but I lack the data to say that definitively. To remove excess chlorophyll, you should use low temperature solvent, extremely dry (like 30% RH in the drying tent with dehumidifiers running) herb, and don’t crush/grind it too much. Trim often only yields 7 to 15% resin that is 60 to 70% potential THC (THCa × 0.877 + THC) or sometimes total cannabinoids. If green is your issue, and you cannot mitigate it with the advive above, you can consider carbon scrubbing, but that will reduce your total cannabinoids in the resin, too. Another option is quick and dirty pressure chromatography over food grade hydrated DE. That grabs and holds onto chlorophyll really well. You will see a green band that darkens or widens, but never moves, using hexane mobile phase. It doesn’t sound like there is enough chlorophyll to affect your percentages, so exposing your dissolved resin to sunlight will turn the green to pale yellow or colorless. Liquid/liquid is not the best for removing trace chlorophyll, but it can work for larger quantities.


#11

awesome advice as always thank you. so on the batch i’m working with currently i distilled 900g of wintereized BHO crude into 1st pass distillate. I have about 490g left now. I recon this stuff is around 70% THC at this point. it is not green anymore. it is a nice amber gold as usual. i had a lot of waste left over in my load flask after the first pass though (almost 180g that wouldn’t distill over).

Do you recommend the saline wash to clean this material up before a second pass?

Thanks,

GH

PS: the outdoor trim i’m dealing with obviously didn’t come from out in-house garden, so i don’t really have control over the drying parameters or the fact that was machine trimmed and destroyed. i understand why it’s green. our in house trims typically yield 13-18% with potency results ranging from 68-82%. This is some of the worst starting material i’ve ever come across, so i’m looking for help.


#12

Eesh… machine trimming is the worst. Good luck!


#13

Is there a particular reason the terpenes would carry over the pesticides while alkanes wouldnt?


#14

I am not certain of the circumstances under which you were told that would be true. Mostly, it depends on the pesticide(s) in question as to whether or not it would be true. In fresh cannabis resin, terpenes coexist with and act as solvents for the cannabinoids. Their capacity to hang onto pesticides is generally greater than that of cannabinoids, so a lot of pesticides go with the terpenes during extraction, distillation, liquid/liquid partitioning, etc. I wouldn’t say it is a question of alkanes vs. terpenes.


#15

Is remediation of 'sauce" really out of the question, then? It should be a distillate to facilitate effective remediation of pesticides, correct?

I have a acquaintance who is saying they can clean dirty sauce, and leave it as sauce, which I think is BS. :joy::stuck_out_tongue_closed_eyes:


#16

Correct. As of now, I don’t know of a way to remove pesticides from resin containing terpenes. I’m sure it depends on which pesticide(s) may be present as to whether or not the resin can be cleaned, but in general, terpenes seem to hang on to many pesticides so much that the pesticide numbers do not even decrease in a statistically significant way when normal resin is put through the removal processes.


#17

I should also include that we have found that some pesticides are practically insoluble in alkanes, and that usually these are pesticides that are quite soluble in water and alcohols. Some terpenes are alcohols called terpenols, aptly enough. By the same token, some terpenes have affinities that alkanes do not, so they may very well hold onto pesticides that alkanes would not.


Where's that degumming thread, Future?
#18

A couple questions from a novice, hope they don’t sound too silly, just looking for some clarification on measuring and adjusting pH.

I am seeking to measure the pH of a dissolved solution of oleoresin in ethanol. The solution is pretty dark pre-scrub and still has that golden amber color post-scrub. Does the color of the solution not affect the ability to read pH on paper? I was thinking of using a probe for this but if litmus paper works I would prefer the low tech solution.

Second, why use magnesium oxide to titrate and not say, sodium bicarbonate.

Thanks!


#19

The solution color does not affect the paper color enough to give you a bad reading.

If you are trying to neutralize something, you should know what it is and what the products will be.


#20

Ah I see so the reason is because of the relative inertness of the magnesium citrate salt formed by magnesium oxide and citric acid, which will have little effect on the end product.

So in my case I don’t know what exactly the acid is that is lowering the pH of my ethanol. I vaguely remember reading about CO2 dissolving in ethanol and forming carbonic acid but I can’t find anything from a basic google search. How could one go about determining the acid present?