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Emulsion Oxidation Problem
Hi there,
I am attempting to formulate a face moisturiser using natural ingredients. Unfortunately I am having some issues in terms of the oxidative stability of the formula (at least I assume it is oxidation). As I have no scientific means of measuring peroxide values etc. I am relying on smell, pH and colour changes.
The formula is:
Water Phase:
Aqua
Oryza Sativa (Rice) Starch
Vaccinium Vitis-Idaea (Lingonberry) Extract & Glycerin
Gluconolactone
Siligel
Sodium Stearoyl LactylateOil Phase:
Glyceryl Stearate
Isoamyl Laurate & Isoamyl Cocoate
Safflower Seed Oil
Cetyl Alcohol
Jojoba Seed Oil
Polyglyceryl-6 Palmitate/Succinate
Mango Seed Butter
Squalane
Chamomile Flower Extract
Sunflower Seed Oil
Tocopherol
Cetearyl AlcoholCool Phase:
Niacinamide
Glycyrrhiza Glabra (Liquorice) Root Extract
Salix Alba (Willow bark) Leaf Extract
Potassium SorbateSadly I cant post percentages so hopefully this is sufficient without.
Originally the problem I had was with the almond smell that the formula was giving off (I was originally using Benzyl Alcohol as my preservative) but I took this out thinking that it was the cause of the issue. This did remove the almond smell but certainly not the oxidation problem. It also led me to believe that the problem is in the water phase of the formula.
The batches I make now all seem to change from a white colour to a feint brown/off white. The smell also changes, it is not overly unpleasant but definitely less pleasant than straight after I have made the batch. I have retested the pH for all of my batches as I know that Gluconolactone has a tendency to cause ph drift but the values have remained consistent over several years. I have tried running knockout tests to work out what the issue is but I just want to see if there are any parameters I am missing.
I first wondered if it was due to a lack of tocopherol. The original formula only has 0.05% but I have since produced batches with concentrations ranging from 0.2-0.5%. No luck.I also wondered whether the lack of an effective chelate could be the issue. I thought gluconolactone would be sufficient but I have recently discovered that it is only effective at a high pH. I do have an old formula that is relatively similar in composition (thought not identical) where I used GLDA and the formula has remained very stable over the course of 3 years. Sadly this also contains green tea and has a higher viscosity so it is difficult to draw conclusions from this.
This brings me onto my next question. The formula mentioned above containing GLDA has a far higher viscosity than my current formula and as mentioned has remained very stable. I know that viscosity does have an impact on oxidation and the rate at which it takes place. If I understand correctly this is mainly due to the ability of oxidation to diffuse through the formula, if so would I be right to imagine that there would be oxidation on the surface if viscosity was the preventing factor in this case? I also wondered whether the increase concentration of emulsifiers might be ‘protecting’ the oil phase from interacting with dissolved oxygen in the water phase?
My final question is in terms of water soluble antioxidants. At the moment I am not using one. I have read that gluconolactone functions as an antioxidant but I assume it is nowhere near effective enough to stabilise a formula. Any suggestions on natural antioxidants that might help? I cant seem to find ergotheonine or NAC but if they are by far the best then I’m sure I could track them down.
Any thoughts on something that I might be missing would be greatly appreciated or methods to prevent oxidation that I should be considering.
Alfie
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15 Replies
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Hi,
could you at least share what the lipid portion? In total?
And extracts?When you state you add Tocopherol into Oil phase. Does that mean you are heating it with all the lipid portion for emulsification?
That might be the problem. Tocopherol (I am guessing you are not using Tocopherol Acetate) is heat sensitive and if you are using it in balm/hot pour, you need to increase its input significantly as some of it does oxidase due to the high temperature.Also, I am not really sure about your preservation system.
Gluconactone does help with preservation of the product, but I would not rely on it. Especially with Potassium Sorbate only. (You have a very nutrient rich formula) -
I think you need to add at least one additional preservative plus 0.25% or so of sodium phytate (chelator), and then come back to us.
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You have only listed a partial preservative, that ONLY works in a given pH range…and NOT listed a pH of the product (or did I miss that in my cursory scan).
I guess my first question is… How do you know your product is not rotting…instead of oxidizing? I guess…I would start by using a proper preservation system, then see how things perform beyond that point. One step at a time.
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@Paprik - The lipid portion is approx 16%. I was told that you should add tocopherol to the oil phases for emulsification otherwise it wouldn’t be in ‘contact’ with the phases it is trying to protect. As for the preservative system, I have tried multiple but this one has passed PET testing at the start and after one year of storage at RT.
@suswang8 - See above as per the preservative. As for sodium phytate this is one of the options I am currently trying. Only issue is that it completely destabilised the siligel in my water phase, any idea why?
@Graillotion - See above as per product rotting. The pH of the product is 4.7.
Thanks for your responses.
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@alfie101 Some oxidation processes can be catalyzed by the presence of metal ions (some extracts have them in significant amounts), and that’s why adding a chelant like GLDA makes sense. Try always having one. I’d also replace the sorbate (tends to contribute with some specific odor) by a more broad spectrum (and less allergenic) combination, like Phenoxyethanol and Sodium benzoate.
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I am testing small amounts of 3 oils ( bitter almond oil, sweet almond oil and unrefined hempseed oil) for oxidation since last year to see what happens at the end.
They are placed in Sunny window, transparent package most of the time. I am sure that they have oxidized a lot because the texture has changed and grainy things has formed specially in sweet almond oil and hempseed oil.
The only thing that hasn’t changed at all is the smell. Bitter almond and unrefined hempseed oil has strong aroma.
So i think your problem is not oil oxidation.After how much time the smell turns bad?
I also think it may be contamination.Have you tested for contamination after the smell and color change?
If not, one simple test would be to add 0.3% EDTA liquid+ 1% DMDM hydantoin, formalin or CMI MI. If the smell changed it means it was contaminated, high load of these strong preservatives killed the microbes and now it is not contaminated, that is why bad smell has gone.
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Ok, thanks for the advice everyone!
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Paprik said:Hi,
could you at least share what the lipid portion? In total?
And extracts?When you state you add Tocopherol into Oil phase. Does that mean you are heating it with all the lipid portion for emulsification?
That might be the problem. Tocopherol (I am guessing you are not using Tocopherol Acetate) is heat sensitive and if you are using it in balm/hot pour, you need to increase its input significantly as some of it does oxidase due to the high temperature.Also, I am not really sure about your preservation system.
Gluconactone does help with preservation of the product, but I would not rely on it. Especially with Potassium Sorbate only. (You have a very nutrient rich formula)Hi! Paprik, tocopherol acetate has no antioxidant protective benefits in formulas, it only provides antioxidant benefits to the skin. It’s a very common mistake though.
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Your product is not properly (weakly) preserved and you’re using Siligel that contains Lecithin which is probably the best nutrient for microbial growth of any ingredient you can use. I suspect your problem is actually microbial contamination.
Try eliminating the Potassium Sorbate and switch to Gluconolactone (and) Sodium Benzoate at 1.25%, but you will need another preservative to cover bacterial contamination.
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naramade said:Paprik said:Hi,
could you at least share what the lipid portion? In total?
And extracts?When you state you add Tocopherol into Oil phase. Does that mean you are heating it with all the lipid portion for emulsification?
That might be the problem. Tocopherol (I am guessing you are not using Tocopherol Acetate) is heat sensitive and if you are using it in balm/hot pour, you need to increase its input significantly as some of it does oxidase due to the high temperature.Also, I am not really sure about your preservation system.
Gluconactone does help with preservation of the product, but I would not rely on it. Especially with Potassium Sorbate only. (You have a very nutrient rich formula)Hi! Paprik, tocopherol acetate has no antioxidant protective benefits in formulas, it only provides antioxidant benefits to the skin. It’s a very common mistake though.
And that is why I said and bolded “NOT” using Tocopherol Acetate.
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naramade said:Hi! Paprik, tocopherol acetate has no antioxidant protective benefits in formulas, it only provides antioxidant benefits to the skin. It’s a very common mistake though.
Not really, the conversion of Tocopherol Acetate to active tocopherol in the skin is only 6% … It’s virtually worthless as an antioxidant.
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Can one you (maybe Mark?) advise what is a good antioxidant to use in an emulsion (say face cream) rather than including Tocopherol and at what % - or isnt there any point putting one in? What about Rosemary Antioxidant as well?
Or should you put an antioxidant into a bottle of Oil such as Grapeseed, Sunflower etc once you open the bottle? Or doesnt this make a difference either. Thanks for your help on probably stupid questions but would like to know for future concoctions I make for myself. I also keep most my oils in wine fridge at about 6 to 10 degrees (as standard room temp where I live is around 25 degrees Celcius year round and humidity between 45 and 65. Cheers and thanks again -
Squinny said:Can one you (maybe Mark?) advise what is a good antioxidant to use in an emulsion (say face cream) rather than including Tocopherol and at what % - or isnt there any point putting one in? What about Rosemary Antioxidant as well?
Or should you put an antioxidant into a bottle of Oil such as Grapeseed, Sunflower etc once you open the bottle? Or doesnt this make a difference either. Thanks for your help on probably stupid questions but would like to know for future concoctions I make for myself. I also keep most my oils in wine fridge at about 6 to 10 degrees (as standard room temp where I live is around 25 degrees Celcius year round and humidity between 45 and 65. Cheers and thanks againYou seem to have two questions….antiOx for a cream…and adding antiOx’s to your oils prior to use.
So, first understand…AntiOx’s work in the phase they are soluble in. Hence in a cream…if you want a full spectrum…you use both oil and water soluble AntiOx’s (The E and Rosemary will only we working in the oil phase). If you only concern is protecting the oils…then you have already listed the two best. If you really want to take it to the very edge…add some Ascorbyl Palmitate, as that is supposed to turbo-charge the MT-E.
As far as your oils….My program is….refrigerate, keep out of light, once opened, I give them a half rate of the MT-E and Rosemary Extract….then repeat the process with a half rate…once they go into formula.
Aloha.
For those down under…use this: 17 ml Vitamin E Natural - 50% Mixed Tocopherols - New Directions Australia
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Thanks G - Yes I basically asked 2 questions
(cheeky I know
I am currently Vit E Nat + 50% Tocopherols from New Directions Aust and RAnti as well So I have been adding these to my cool down phase once I emulsify - I assume that this is wrong by your comments and I should be adding to the Oil Phase - I thought that the 50% Mixed Tocopherols (New Directions one) was intolerant to heat above 70 degrees? If I add to my Oil phase I know I would need to use more so what % would you recommend (along with Rosemary Antioxidant) or dont I need both? 50% Mixed T is much cheaper and too much RAnti gives me too much colour in the cream.And good to know I should be adding both to my oils once I open (and yes I keep in my special fridges for my raw ingredients out of light too).
Cheers and thanks again. -
If you are worried about oxidative stability of your formulation, it’s probably worth replacing highly unsaturated oil like safflower with other emollients. Moreover, make sure to use high oleic sunflower oil. As other have already stated, you also need to make sure your preservative system is adequate.
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