Brainstorming: Experiences with Preservatives, Antioxidants, and Chelating agents in Soap

[elurah]

Hi all,

Discussion in another thread concerning DOS prompted my interest in additives that reduce the risk of fatty acid oxidation and rancidity in soap.

http://cavemanchemistry.com/DreadedOrangeSpot-Dunn.pdf

This paper mentions different combinations including ROE +EDTA and BHT + Sodium Citrate. A few members use these strategies already (cmzaha, DeeAnna, Earlene, I believe?). However, it was published in 2006 and I am interested in not only reproducing Dr. Dunn's findings but also in testing out new antioxidants and chelators that may have been developed or have become more popular since publication.

Any experience with methods or materials would be greatly appreciated! I plan to send an email to Dr. Dunn with my setup to see if everything checks out. For now I would love to brainstorm with you all or here your experiences working with these agents in soap.

I. Method

I think I have two possible options.

1. I could reproduce the original study. I am just interested in the additives so I do not have to worry about the nitrogen vs oxygen tubes. I would use the standard soap recipe mentioned (Recipe #1) in the paper and my own recipe (20% SF) (Recipe #2). I would need an incubator, a scanner, a computer w/ free program download, disposable plastic pipettes, beaker holder, and the additives.

Study Design would be:
Recipe #1: Negative Control 1, Negative Control 2, Additive 1, Additive 2, Additive 3, etc.
Recipe #2: Negative Control 1, Negative Control 2, Additive 1, Additive 2, Additive 3, etc.

2. I could find a lab that has a rancimat machine and ask them if they will run samples for me for a fee. If anyone has one or knows a lab that does in the continental US, let me know!

II. Additives
** If you have others you have tried or are interested in learning more about, let me know! I am interested in "greener" antioxidants and chelators, with regards to their environmental impact and their label appeal.

Antioxidants
1. ROE
2. Tocopherols/Vitamin E

Chelators
1. EDTA
2. Sodium Citrate
3. Sodium Ascorbate
4. Sodium Gluconate (https://www.makingcosmetics.com/Sodium-Gluconate-USP_p_1103.html)
5. Tetrasodium Iminodisuccinate (Baypure CX 100)
- It says it can be used for cosmetic use but I can't find much info about it
6. Sorbitol??
- No idea this had chelating abilities in alkaline conditions. My question is, how alkaline does it need to be for it to chelate?

Combinations
3. ROE + EDTA
4. ROE + Sodium Citrate
- It performed worse the first time, I am interested in rechecking this
5. Ascorbic Acid (ascorbate as chelator) + ROE + Tocopherols (http://www.theherbarie.com/Antioxidant-Synergy-Blend-ASB.html)
6. ROE + Sodium Gluconate

Resources:
http://www.subsport.eu/wp-content/u..._ions_removal_from_different_waste_waters.pdf

https://onlinelibrary.wiley.com/doi/pdf/10.1002/9783527628698.hgc104
(^ anyone have access to this article? Woudl lvoe to read it)

https://www.alliedmarketresearch.com/green-chelating-agent-market

 

[OrganicSoapGuy]

We find that the levels of linoleic FA have a consistent correlation with DOS. That is, the higher the linoleic level, the faster and more pervasive the spots. If you're reproducing the above experiment testing various additives, I'd also explore how the additives do with a formulation that has higher levels of poly-unsaturated fatty acids. Rather than using an all OO recipe like the cavemanchemistry article to test the various additives, I think it would be highly interesting to look at how well the same additive (single, or the same combo) works in an OO recipe and high poly-unsaturated recipe (such as using soy or a non-HO sunflower). For some greater consistency, you could compare a 100% HO sunflower recipe with a non-HO sunflower.

Also, be super careful/consistent with all temperatures from start to finish. Variations in heat between batches during saponification will affect the reactivity of any of the non-saturated FA's, even mono-unsaturated ones like oleic. Even if you have two identical formulas (oils and additives), you'll likely see more spots in one batch compared to the other if there is a significant difference in the temperatures.

Make sense?

 

[cmzaha]

I can say I used regular sunflower and canola for several years usually at 20% up to 40% keeping the soaps up to a year and no dos. So there are certainly other factors in play with dos than FA's. I am not saying 100% regular sunflower or canola will not get dos.

 

[penelopejane]

Elurah
In your links they use GLDA which is not sodium gluconate but can they be used interchangeably for the sake of those experiments?

I am happy to accept sodium gluconate is a good chelating agent but I’m not sure what percentage to use in soap.

I want to use it to stop soap scum. CA is problematic for me.
I’ve made testers of 0.5% and 1% but other than waiting to see if my floor waste gunks up how do I tell how effective each is?

 

[elurah]

We find that the levels of linoleic FA have a consistent correlation with DOS. That is, the higher the linoleic level, the faster and more pervasive the spots. If you're reproducing the above experiment testing various additives, I'd also explore how the additives do with a formulation that has higher levels of poly-unsaturated fatty acids. Rather than using an all OO recipe like the cavemanchemistry article to test the various additives, I think it would be highly interesting to look at how well the same additive (single, or the same combo) works in an OO recipe and high poly-unsaturated recipe (such as using soy or a non-HO sunflower). For some greater consistency, you could compare a 100% HO sunflower recipe with a non-HO sunflower.

Also, be super careful/consistent with all temperatures from start to finish. Variations in heat between batches during saponification will affect the reactivity of any of the non-saturated FA's, even mono-unsaturated ones like oleic. Even if you have two identical formulas (oils and additives), you'll likely see more spots in one batch compared to the other if there is a significant difference in the temperatures.

Make sense?

Makes sense! I was planning to do OO + my own recipe which is pretty low in linoleic, but I agree it would be really interesting to test the polyunsaturated fats. I need to work out what would be the best set up and procedure to minimize contamination and extrinsic factors like temperature differentiation between batches. I was going to include to two negative controls and two of each sample, but I don't have a great way to mininize differences among recipes other than having an consistent procedure. I hear you on the temp differences, I use an infrared thermometer and I pretty much always soap within a 4 degree range (98-102)

 

[elurah]

Elurah
In your links they use GLDA which is not sodium gluconate but can they be used interchangeably for the sake of those experiments?

I am happy to accept sodium gluconate is a good chelating agent but I’m not sure what percentage to use in soap.

I want to use it to stop soap scum. CA is problematic for me.
I’ve made testers of 0.5% and 1% but other than waiting to see if my floor waste gunks up how do I tell how effective each is?

Hi! So it 's a bit difficult because that first link has great science but is specific to industrial waste water treatment. Looking through the websites and what items I could actually buy small scale, I came across info on Sodium gluconate. Even though this is different from GLDA, the principle should be the same and it has precedence being used in other cosmetic products.

Great questions about how to tell if a chelator is working or not! I am especially interested in this since a lot of these materials have been studies with regards to their capicity with straight oils, or oil/water products, but not soap!

I found this article which provides some laboratory tests for measuring lipid perixodation, antioxidant effect, free radical scavenging, and chelating:

I think I understand the procedures but it requires some serious equipment including a centrifuge, a crap ton of lab chemicals, and an absorbance spectrophotometer (???) which I do not have handy. So I need to look into better ways to conduct these tests at home. Always more questions. I will keep you posted!

Warmly,
Allie