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Soap making, defatting, and extraction chemistry

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T

Tribal

Rising Star
To start, let me say that I used to make soap. There seems to be a lot of similarities between the soap making process and spice extraction, in that fats and lye are typically involved.

Now, with MHRB, the fats and oils aren't that much of a problem, making the STB tek a useful choice. However, with Phalaris or other sources, most do an A/B so that a defatting can be done before extraction.

Something occurred to me about this process, and I was hoping someone with a little more chemistry knowledge could explain this. Soap is made by a process called saponification, which, in soap making, is the reaction of fats and oils with lye. Soap is water soluble, and, so if it existed in the basic solution a non-polar solvent shouldn't pull it, correct?

So, my question is, once lye is added to make the solution basic, the fats and oils should be saponified (made into soap), and shouldn't be pulled with the NP solvent. So, why is defat necessary at all?
 
Tribal said:
To start, let me say that I used to make soap. There seems to be a lot of similarities between the soap making process and spice extraction, in that fats and lye are typically involved.

Now, with MHRB, the fats and oils aren't that much of a problem, making the STB tek a useful choice. However, with Phalaris or other sources, most do an A/B so that a defatting can be done before extraction.

Something occurred to me about this process, and I was hoping someone with a little more chemistry knowledge could explain this. Soap is made by a process called saponification, which, in soap making, is the reaction of fats and oils with lye. Soap is water soluble, and, so if it existed in the basic solution a non-polar solvent shouldn't pull it, correct?

So, my question is, once lye is added to make the solution basic, the fats and oils should be saponified (made into soap), and shouldn't be pulled with the NP solvent. So, why is defat necessary at all?
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someone correct me if I'm wrong but isn't soap soluble in both polar and non-polar solutions(which is why it is used to get rid of oils, 1 end dissolves in water and the other in the oil
 
I should have done a little more research before posting. Yes, that's exactly how it works. It's sort of pseudo-soluble in either, and likes to reside at a boundary between the two.

Still, wouldn't you actually be extracting soap instead of fats/oils?
 
Depends on a few things:

1) are the conditions right? i.e. :

i.is there enough lye in an MHRB STB to hydrolyse the fatty acid esters? Could it be that STB uses too much lye and interferes with saponification?
ii. are any other requirements ok? can saponification be performed at room temperature?

2) why assume that soap molecules are soluble in the NP solvents used in spice extraction? Soap is a salt strictly speaking. Even though it has a fairly large lipid moiety attached to it (which could give it some affinity for NP solvents) the presence of polar and most importantly charged moiety would render it insoluble to NP solvents.

The latter means that yes, some lipids could get saponified in an STB, but they would dissolve in the fairly aqueous environment of an STB. And since they would dissolve, they would get charged (this is what "dissolving" means in this case) and would thus not get picked up by NP solvents.

So, lipid esters can get saponified but they would not be picked up by NP solvents. Other lipids (not esters) would be picked up by NP solvents.

The saponification thing is very interesting though, it could explain the concept of emulsions; soap molecules would love to live on the interface between the polar (water) and non-polar (naphtha, xylene, whatever), in concordance to their bivalent lipophilic/hydrophilic nature.
 
Infundibulum said:
The saponification thing is very interesting though, it could explain the concept of emulsions; soap molecules would love to live on the interface between the polar (water) and non-polar (naphtha, xylene, whatever), in concordance to their bivalent lipophilic/hydrophilic nature.
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That is exactly why you don’t bring the pH up to 11 or higher when doing an extraction with fatty substances like yopo, chacruna or chaliponga. Doing so causes horrible emulsions because lots of soaps form. Mimosa, on the other hand, is very low in fat so this doesn’t pose much of a problem.

Note that only certain bases are able to form soaps. Sodium bicarbonate (gets to about 8.3 max) cannot form soaps, but sodium carbonate can if enough is used (it can get to pH 11.4). If you’ve ever felt wet sodim carbonate, you’ll notice that it feels soapy. It’s not soapy. It feels soapy because it’s reacting with the fats in your skins to form soap. Saponification does not require heat.
 
69ron said:
Infundibulum said:
The saponification thing is very interesting though, it could explain the concept of emulsions; soap molecules would love to live on the interface between the polar (water) and non-polar (naphtha, xylene, whatever), in concordance to their bivalent lipophilic/hydrophilic nature.
Click to expand...

That is exactly why you don’t bring the pH up to 11 or higher when doing an extraction with fatty substances like yopo, chacruna or chaliponga. Doing so causes horrible emulsions because lots of soaps form. Mimosa, on the other hand, is very low in fat so this doesn’t pose much of a problem.

Note that only certain bases are able to form soaps. Sodium bicarbonate (gets to about 8.3 max) cannot form soaps, but sodium carbonate can if enough is used (it can get to pH 11.4). If you’ve ever felt wet sodim carbonate, you’ll notice that it feels soapy. It’s not soapy. It feels soapy because it’s reacting with the fats in your skins to form soap. Saponification does not require heat.
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but for example one of the very effective ways of removing/preventing emulsions in an STB is to add more NaOH.. It works very well..

so maybe saponification has a pH range that it can occur, not lower and also not higher.. right?
 
Like it said, mimosa has very little fat so saponification is not an issue no matter what the pH is. If it had lots of fats and you took the pH to 14, you'd have horrible emulsions like you get with the leafy material. Try it out and you'll see what I'm talking. Add some fat to your mimosa and try an STB at pH 14 and see what kind of nightmare emulsions you create. HA HA HA.
 
but for example one of the very effective ways of removing/preventing emulsions in an STB is to add more NaOH.. It works very well..
Click to expand...

Hmmm. Saponification occurs more the higher the pH. When making soap, each oil or fat has a "sap" value, indicating how much lye needs to be added to completely saponify it. If less lye is added than the sap value, you get a "super-fatted" soap with residual fats and oils that aren't saponified. These are softer, but can get funky and over time. If too much lye is added it will be completely saponified with residual lye raising the pH, which can burn the skin.

So, like 69ron said, more soaps would form at higher pH. So, why is this a good recommendation for reducing emulsions if it is indeed soaps that cause emulsions?

My friends cousin's dog's sister's owner's Chia pet had a dream where a weird soapy looking emulsion formed between the NP and aqueous layers during a STB extraction. It took some mild agitation to break up and never really settled completely. Raising the pH didn't help that poor, fuzzy grassy looking little guys situation at all.

While we're on the subject, what is the best way to reduce emulsions? Has anyone had any luck getting rid of them once they form?
 
It makes sense to me; Soap will difficultly dissolve in hard water, i.e. water with high salt content. I had bad experiences trying to use soap in areas where tap water was more salty than usual.

Increasing the ionic strength of the solution (by adding loads of salt or lye) seems to have a positive effect on preventing these emulsions. Not sure about the mechanism though.

When soap "dissolves" in water to make foam it forms a colloidal suspension, a mixture of soap droplets, water and air. If the water is salty it will not do so and will look like trying to mix water with wax or vaseline. In the latter case the soaps have failed to dissolve and behave like lipids rather than soaps.

What can possibly hint to it is chemical equilibria. if soap dissolves in this manner:

Soap-COONa <--> Soap-COO- + Na+

So possibly addition of extra sodium in the solution (add more NaOH or NaCl) will push the dissolution reaction to the left, making soaps undissolved and thus not emulsion forming?
 
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