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Essential Oils and Lamellar Emulsion Stability
Are there any essential oil constituents that have an impact on O/W lamellar emulsion stability? Either disrupt it or help stabilize it?
If this is too general a question, the specific emulsifier and co-emulsifier I am interested in both contain lecithin: Heliosoft (Glyceryl Behenate (and) Behenyl Alcohol (and) Lecithin) and Siligel (Xanthan Gum (and) Lecithin (and) Sclerotium Gum (and) Pullulan.
If yes, what is the mechanism of action?
Thank you.
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10 Replies
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Yes, there are; such which disrupt and such which stabilise. Depends on the whole blend (really, the WHOLE cocktail, not just an EO meeting an emulsifier) and this is, by common means, totally impossible to predict ;( .There are several mechanisms in play, some are somewhat understood, others are educated guesses and extrapolations, and the rest is speculations & hypotheses.As a general rule of tumbs, I would say (and this is pure assumption) that the chances that an EO destabilises a lamellar structure is more likely than the opposite. Unsaturated, branched, or cyclic hydrocarbon EO constituents are more likely to have a negative than a positive impact on liquid crystal structures but are tendentially the ones with the lowes chance to actually interfere with the emulsifier layer. Ketone and aldehyde EO constituents… dunno… probalby close to the aforementioned ones. Phenolic EO constituents have a high chance to actually do something with an emulsion but the effect may be either way (depending on everything) with maybe, just maybe, a higher chance for a positive outcome due to them interacting more likely with the interface than the oil phase. Alcohol groupe containing EO constituents are probably the ones which have the highest possibility of negatively interfereng with liquid crystal structures due to them intercalating with the emulsifier/co-emulsifier tails. Functionalised monoterpenes are also more likely to interact with emulsifier layers than the more lipophilic diterpene counterparts whilst corresponding sesquiterpenes are likely the ones which most readily interlocate with the crystalline part of the interface.Generally, unsaturation, branching, and cyclic structures are more likely to reduce rigidity of lamellae and introduce defects into crystal structures, no matter whether they are part of the emulsifier, the oil phase, or some added actives or essential oil. Except some phenolics, most EO constituents have one or several of these structural elements, that’s the reason why most are low viscosity liquids and likely also why people more often complain about EOs killing their emulsions than raving about their benefits for stability.Again, this is speculation and a not very helpful one at that either. This is because essential oils are usually blends of dozens to hundreds constituents very often comprising most of the abovementioned chemical families with highly fluctuating composition between batches…Bottom line is: Best add EOs only after lamellar structures have been formed, dont add too much EOs, and add them together with a solubiliser. Alternatively, include them into an oil phase and add lamellar structure builders as separate phase. Both strategies would reduce the chances that EO constituents meet crystalline structures. -
@Pharma THANK YOU so much for taking the time to respond in such great detail. I’ve learned so much from your post.
When you say add the EOs to an oil phase, and add the lamellar structure builders as a separate phase, I’m assuming you mean add the EOs to a cool-down oil phase since most EOs have lower flash points than the hot oil phase.
Should I briefly homogenize at the end of cool-down in order to ensure EO’s are incorporated properly?
Thank you!
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Anca_Formulator said:…
When you say add the EOs to an oil phase, and add the lamellar structure builders as a separate phase, I’m assuming you mean add the EOs to a cool-down oil phase since most EOs have lower flash points than the hot oil phase.Should I briefly homogenize at the end of cool-down in order to ensure EO’s are incorporated properly?
…No, I’m not saying how you do it exactly, I’m just saying that using certain strategies/techniques could work. How you do it precisely… that’s up to you and the emulsifier/LGN promotor you’re using
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I just made a similar post asking for help. My chamomile EO destabilized my Heliosoft + Siligel emulsion.
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@coco: Yikes!! I’m quite anxious myself to see what the EOs I’ve tried are doing to stability. In progress. Will report back…
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@Anca_Formulator it seems like you and I are dead set on using this emulsifier. I’ve read your suggestions also the guidelines working with this emulsifier. I’ve spent so much money and time trying to make it work. Yes the formula has improved as in not destabilizing instantly however the formula remains weak and you can see separation when you look closely. To say that I am sick an tired it’s an understatement! I have been on this since May of last year. Out of all the products I have formulated (and there were some truly challenging ones), this one remain my absolute headache!! I finally reached out to the manufacturer. Truly hope they can help.
The product I am making is a pretty simple one, as it is intended for the most sensitive skin. There is nothing crazy in it. In fact, I have made this multiple times with different emulsifiers without problems. Playing around emulsifiers and co-emulsifiers too much with Heliosoft does end up changing the skin feel of my product which defeat the whole purpose of this product. The product was inspired by Heliosoft, so taking it out or making it co-surfactant is just not working for me. I am going bald!! -
coco said:@Anca_Formulator it seems like you and I are dead set on using this emulsifier. I’ve read your suggestions also the guidelines working with this emulsifier. I’ve spent so much money and time trying to make it work. Yes the formula has improved as in not destabilizing instantly however the formula remains weak and you can see separation when you look closely. To say that I am sick an tired it’s an understatement! I have been on this since May of last year. Out of all the products I have formulated (and there were some truly challenging ones), this one remain my absolute headache!! I finally reached out to the manufacturer. Truly hope they can help.
The product I am making is a pretty simple one, as it is intended for the most sensitive skin. There is nothing crazy in it. In fact, I have made this multiple times with different emulsifiers without problems. Playing around emulsifiers and co-emulsifiers too much with Heliosoft does end up changing the skin feel of my product which defeat the whole purpose of this product. The product was inspired by Heliosoft, so taking it out or making it co-surfactant is just not working for me. I am going bald!!Have you tried combining the EO’s with TEC (triethyl citrate) before introducing them?
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@Graillotion no, I haven’t. Yeaah, another ingredient I have to look for, how fun! Lol thank you so much tho. Honestly I doubt EO may even be the issue. Last time I made it, I added everything that was not pure water, glycerine, gums and emollient at the cool down phase at 35C. I could start seeing instability (around the glass) before adding any cool down ingredient. Right now everything looks solid after 3 days however I can definitely see separation around the edges when I look close. Can you believe I even change supplier at some point? Urg..
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With that emulsifier…one could hope for little better than a salad dressing.
@coco .If you are set on using it… then use it…but add some real emulsifiers to help it out.
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@Graillotion lol will sure do, thnx.
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