I’m curious as to how omega-3’s play into soap making. Usually omega-6’s are the focus of polyunsaturated fatty acid conversations due to high linoleic concerns. I’ve noticed that most popular soaping oils are very low in omega-3’s, that seems to be the most common quality they have in common. I’ve also noticed that canola has a much more proportional representation of omega 6’s and 3s than most vegetable, nut and seed oils. Canola oil seems to put a lot of soap makers off, or at least quiet them. It’s viewed as a subpar oil, yet on paper it shouldn’t be. When balanced with high linoleic soft oils it’s easy to get a fatty acid profile that works on paper. And when mixed with a high oleic oil it can raise the linoleic value for us linoleic fans (I’m looking at you @ResolvableOwl) That being said, I’ve experienced DOS using canola when it doesn’t seem like I should in the calculator (8 months cure, random DOS). I know that omega-3s don’t fare well with high heat. I’m curious, what kind of breakdown occurs with omega-3s at higher temperatures? What does it turn into? Are gelling temperatures high enough to decompose omega-3 structures? And could the aftermath of high heat and omega 3s contribute to DOS? Make a cup of tea @DeeAnna, I’m looking at you… no pressure
The dash between ω (omega) and the number is in fact a minus sign. It's pronounced “omega minus three”. The outermost double bond is at the third carbon atom, counted from the last (omega) atom of the chain.
First, a bit of nitpicking. The ω–N notation is AFAIK motivated from biochemistry (ability of some enzymes to work with double bonds at differnet locations of a FA chain), and as such is in some way not a good classification scheme for PUFAs. (Take all this with a grain of salt, since I'm by far not an expert in PUFA (bio)chemistry.) The N of the ω–N class only tells you where the outermost double bond is located. It does not tell you how many double bonds are in the FA, and how far they are apart – but these are exactly the things that define the reactivity of FAs (in soapmaker's terms: their proneness to attack by oxygen, i. e. rancidity/DOS). There are monounsaturated ω–3 and ω–6 FAs, as well as di-unsaturated and tri-unsaturated ω–9 FAs (albeit exotic) (albeit they are all exotic).
IIRC, the double bonds themselves are not the main site of attack (e. g. by atmospheric oxygen), but the saturated carbon just next to them (called the “allylic” carbon). Now, most PUFAs that Nature has come up with, have allylic chains (pairs of double bonds, separated by a single, shared allylic carbon), like the “normal” linoleic and linolenic FAs. Each of the intermediate allylic carbons in these chains is a neighbour of two instead of one double bond, which amplifies the reactivity at this site. AFAIK this is what makes PUFAs so much more reactive (rancidity prone) than MUFAs (where the rest of the molecule apart from the single double bond is just a straight, saturated chain).
I don't have good sources at hand atm, but there are hints from the reactivity towards hydrogen: as per making canola wax from canola oil – note how fast the 18:3 number vanishes, its half-life is roughly half of that of the 18:2. Of course hydrogenation is not DOS, but similar wisdom has anecdotally found relevant for the reactivity of linolenic oils when compared to linoleic oils – at similar iodine values.
BUT all this does not apply to all PUFAs, just those with allylic chains. (There are also conjugated PUFAs, i. e. those where the double bonds are directly next to each other, but these have an entirely different reactivity.)
As another counterexample, take 9,15-Octadecadienoic acid (ω–3 but isolated double bonds). Is this a PUFA? It sounds like one, given it has multiple double bonds. Does it behave like a PUFA wrt oxidative rancidity? Likely not, since the double bonds (and their respective allylic carbons) “don't know from each other”. Does it behave like a PUFA in soap? I'd love to know, but I have not the slightest idea.
So much for the introduction, that actually should just elaborate why I think you actually mean di-allylic PUFAs when you say “ω–6”, and three-or-more-allylic FAs when you say “ω–3”. (Probably the best real-world example is γ-linolenic acid, a ω–6 FA like regular α-linolenic acid, just some parts of the saturated carbon chain shuffled from the front to the back, but it's still a tri-unsaturated/tri-allylic FA.)
In practice, this all doesn't matter so much, since for the overwhelming majority of oils, di-unsaturated FAs is essentially exclusively ordinary linoleic acid (ω–6), and tri-unsaturated is mostly α-linolenic acid (ω–3). Only few oils accessible to humble humans (hemp, fish oil) have significant amounts of PUFAs that don't fit into this simplification.
Now to your actual point(s). First, a clarification! Yes, I have started that infamous “Linoleics” thread. But I didn't do that to play off the PUFAs against each other. I have nothing against a good share of linolenic acid in my soaps, I just am, for the above reasons, even more cautious with it than with linoleic acid. I have used flaxseed and camelina oil in double-digit percentages with decent success. The one thing to keep in mind is that these oils give notoriously soft soap, so it might be in order to slightly exceed one's customary comfort zone of hardness/longevity number. I suspect that this is one of the reasons for discouraging linolenic oils for soapmaking – it is really hard (no pun intended) to get bars of decent longevity when using good amounts of these.
Regarding canola: I've used canola at 60% (with the usual rancidity countermeasures in place: antioxidants, chelators) and was not disappointed. I don't see a particular antipathy for canola. In fact, BB's “Swirl” oil blend contains canola oil. Canola too makes decent LS (at an unbeatable price, for those who live in a growing country).
And then, the quality of these oils can indeed vary wildly. I am not sure if refining does any good to them, but on the other hand, their strong colours can impair the usability. Any heating can be detrimental (isomerisation to trans fats, polymerisation, decomposition, hydrolytic cleavage). Spent canola oil used for frying might be okay for biodiesel, but I'd avoid it in soap.
Guess why all these oils are so high in vitamin E? Because the plants knows how fragile these PUFAs are, hence they protect their seeds from oxygen with tons of their antioxidant.
Soaping temperatures & PUFA deterioration: this is likely even more complicated. Why is it more dangerous to have PUFAs floating around as free, neutral/partially saponified oils (superfat), than it is when fully turned into soap? It's the same molecules, but for some reason they are more oxidation prone when esterified than as soap (isolated anions). I have no idea why. But this means that the answer “to gel or not to gel” isn't that easy – not even “CP or HP”: The hotter the reaction runs, the quicker are the PUFA triglycerides converted into PUFA soap, lowering their reactivity and quicker “protecting” them, in some sense that is unclear for me, from the worst fate of turning bad over time. HP also means that you can fully saponify the PUFA oils, and then add a less rancidity prone low-PUFA oil as late superfat. NMR studies of the Dunn group have found out that the more unsaturated an oil is, the slower it reacts (CP or HP), hence in CP the PUFAs tend to be “left over” in the more dangerous state of free-floating superfat, while in HP you can actively influence the order of saponification by just adding oils at different times. Hence, as contradicting as it sounds, a “hotter” process can indeed be more gentle to heat-sensitive ingredients than a “cold” process. Is it really? There are so many external factors, that I think it's safe to say that we just can't know.
tl;dr: It appears appropriate to treat poly-allylic oils with all due respect (antioxidants, chelators, with storage dark, dry, and not too warm). They're likely in better hands at HP and liquid soap than traditional CP. Do they contribute particular properties to the soap? In the end, everyone has to know by themselves (i. e. find out) if they fit into their respective conception of how a soap should work and how it should feel like.
The dash between ω (omega) and the number is in fact a minus sign. It's pronounced “omega minus three”. The outermost double bond is at the third carbon atom, counted from the last (omega) atom of the chain.
First, a bit of nitpicking. The ω–N notation is AFAIK motivated from biochemistry (ability of some enzymes to work with double bonds at differnet locations of a FA chain), and as such is in some way not a good classification scheme for PUFAs. (Take all this with a grain of salt, since I'm by far not an expert in PUFA (bio)chemistry.) The N of the ω–N class only tells you where the outermost double bond is located. It does not tell you how many double bonds are in the FA, and how far they are apart – but these are exactly the things that define the reactivity of FAs (in soapmaker's terms: their proneness to attack by oxygen, i. e. rancidity/DOS). There are monounsaturated ω–3 and ω–6 FAs, as well as di-unsaturated and tri-unsaturated ω–9 FAs (albeit exotic) (albeit they are all exotic).
IIRC, the double bonds themselves are not the main site of attack (e. g. by atmospheric oxygen), but the saturated carbon just next to them (called the “allylic” carbon). Now, most PUFAs that Nature has come up with, have allylic chains (pairs of double bonds, separated by a single, shared allylic carbon), like the “normal” linoleic and linolenic FAs. Each of the intermediate allylic carbons in these chains is a neighbour of two instead of one double bond, which amplifies the reactivity at this site. AFAIK this is what makes PUFAs so much more reactive (rancidity prone) than MUFAs (where the rest of the molecule apart from the single double bond is just a straight, saturated chain).
I don't have good sources at hand atm, but there are hints from the reactivity towards hydrogen: as per making canola wax from canola oil – note how fast the 18:3 number vanishes, its half-life is roughly half of that of the 18:2. Of course hydrogenation is not DOS, but similar wisdom has anecdotally found relevant for the reactivity of linolenic oils when compared to linoleic oils – at similar iodine values.
BUT all this does not apply to all PUFAs, just those with allylic chains. (There are also conjugated PUFAs, i. e. those where the double bonds are directly next to each other, but these have an entirely different reactivity.)
As another counterexample, take 9,15-Octadecadienoic acid (ω–3 but isolated double bonds). Is this a PUFA? It sounds like one, given it has multiple double bonds. Does it behave like a PUFA wrt oxidative rancidity? Likely not, since the double bonds (and their respective allylic carbons) “don't know from each other”. Does it behave like a PUFA in soap? I'd love to know, but I have not the slightest idea.
So much for the introduction, that actually should just elaborate why I think you actually mean di-allylic PUFAs when you say “ω–6”, and three-or-more-allylic FAs when you say “ω–3”. (Probably the best real-world example is γ-linolenic acid, a ω–6 FA like regular α-linolenic acid, just some parts of the saturated carbon chain shuffled from the front to the back, but it's still a tri-unsaturated/tri-allylic FA.)
In practice, this all doesn't matter so much, since for the overwhelming majority of oils, di-unsaturated FAs is essentially exclusively ordinary linoleic acid (ω–6), and tri-unsaturated is mostly α-linolenic acid (ω–3). Only few oils accessible to humble humans (hemp, fish oil) have significant amounts of PUFAs that don't fit into this simplification.
Now to your actual point(s). First, a clarification! Yes, I have started that infamous “Linoleics” thread. But I didn't do that to play off the PUFAs against each other. I have nothing against a good share of linolenic acid in my soaps, I just am, for the above reasons, even more cautious with it than with linoleic acid. I have used flaxseed and camelina oil in double-digit percentages with decent success. The one thing to keep in mind is that these oils give notoriously soft soap, so it might be in order to slightly exceed one's customary comfort zone of hardness/longevity number. I suspect that this is one of the reasons for discouraging linolenic oils for soapmaking – it is really hard (no pun intended) to get bars of decent longevity when using good amounts of these.
Regarding canola: I've used canola at 60% (with the usual rancidity countermeasures in place: antioxidants, chelators) and was not disappointed. I don't see a particular antipathy for canola. In fact, BB's “Swirl” oil blend contains canola oil. Canola too makes decent LS (at an unbeatable price, for those who live in a growing country).
And then, the quality of these oils can indeed vary wildly. I am not sure if refining does any good to them, but on the other hand, their strong colours can impair the usability. Any heating can be detrimental (isomerisation to trans fats, polymerisation, decomposition, hydrolytic cleavage). Spent canola oil used for frying might be okay for biodiesel, but I'd avoid it in soap.
Guess why all these oils are so high in vitamin E? Because the plants knows how fragile these PUFAs are, hence they protect their seeds from oxygen with tons of their antioxidant.
Soaping temperatures & PUFA deterioration: this is likely even more complicated. Why is it more dangerous to have PUFAs floating around as free, neutral/partially saponified oils (superfat), than it is when fully turned into soap? It's the same molecules, but for some reason they are more oxidation prone when esterified than as soap (isolated anions). I have no idea why. But this means that the answer “to gel or not to gel” isn't that easy – not even “CP or HP”: The hotter the reaction runs, the quicker are the PUFA triglycerides converted into PUFA soap, lowering their reactivity and quicker “protecting” them, in some sense that is unclear for me, from the worst fate of turning bad over time. HP also means that you can fully saponify the PUFA oils, and then add a less rancidity prone low-PUFA oil as late superfat. NMR studies of the Dunn group have found out that the more unsaturated an oil is, the slower it reacts (CP or HP), hence in CP the PUFAs tend to be “left over” in the more dangerous state of free-floating superfat, while in HP you can actively influence the order of saponification by just adding oils at different times. Hence, as contradicting as it sounds, a “hotter” process can indeed be more gentle to heat-sensitive ingredients than a “cold” process. Is it really? There are so many external factors, that I think it's safe to say that we just can't know.
tl;dr: It appears appropriate to treat poly-allylic oils with all due respect (antioxidants, chelators, with storage dark, dry, and not too warm). They're likely in better hands at HP and liquid soap than traditional CP. Do they contribute particular properties to the soap? In the end, everyone has to know by themselves (i. e. find out) if they fit into their respective conception of how a soap should work and how it should feel like.
Thank you for your thoughtful response! I had to read your post over and over because it contains so much information I couldn’t absorb it all in one read Excellent information!!
@ResolvableOwl .... I've read through it twice and each time I grasp a bit more. When I first started soaping, for a time, I replaced Olive with canola because it was less expensive and a lighter color compared to my OO. I always would find DOS hiding in my soap closet months later. That was before I started using Citric Acid and I've never tried ROE. I have it, just never researched exactly how to use it!. Hemp Oil is also a soap I've always had issues with DOS. I made a batch about a month ago. I'm now adding Citric Acid and I think the batter heated up and accelerated and definitely gelled (Is that good or bad?!?!). I keep checking it periodically and no ugly yellow spots! There is still hope for Hempseed oil!?!?! But now I've fallen in love with HO Sunflower Oil in place of Olive and have given up on trying canola again. Maybe the next time I make the confetti soap to donate. I'll figure out the ROE and double down on the Citric Acid and see how it cures!!!!
