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Rancid odor in final product, but raw ingredients still smell fine
Hello,
I am formulating a face moisturizer (see formula below) for my small business. Currently undergoing stability testing, and it has been 1 month since making the product. Everything is good so far, except the odor. The final product has gone from a faint peppery scent (from the black seed oil) to a rancid odor. Most raw ingredients used, particularly the oils and butter, were new when making the product.
I’ve been trying to figure out what has caused the rancidity. I checked the raw ingredients, and they have not gone rancid and still smell as they did when I first opened them. The pH of the final product still remains the same between 4.5 and 5.0. Any ideas of what could be causing the odor? Is there anything I need to add or change in my formula to avoid the rancid odor?
Heated Water Phase:
Water q.s. 100%
Sodium phytate 0.2%
Propanediol 4%
Glycerin 4%
Sepimax zen 0.3%
Heated Oil Phase:
Olivem 1000 2.5%
Glyceryl stearate 1%
Cetyl alcohol 1.3%
Refined shea butter 2%
Isoamyl laurate 2%
Pomegranate sterols 1%
Cool Down Phase:
Allantoin 0.3%
Dimethicone 1%
Black seed oil 1.5%
Irish moss extract 0.2%
Sodium benzoate 0.35%
Lotioncrafter PE 9010 1%
Mixed tocopherols T50 0.1%
Lactic acid (pH adjuster)
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7 Replies
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Forgot to mention that sodium phytate, sepimax zen, and allantoin are the only older ingredients that I have because it takes me so long to go through them. Could the sodium phytate be the issue here? Maybe it has lost its chelating properties? I’m not really sure if that would cause a rancid odor though, and the color/appearance of the final product has not been affected.
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Check for micro contamination. Even if clean, your product is very poorly preserved.
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After reading the discussions around here, I was under the impression that a good preservation system includes PE 9010 (bactericide) + sodium benzoate (fungicide) + chelator + glycol/diols + pH 4.8.
Should I add caprylyl glycol? I thought propanediol and glycerin would fall into that category of glycol/diol preservative boosters.
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Sorry! My error - was distracted with “Lotioncraft” and missed the PE. That should be a good system.
Still - have you checked for micro contamination? That is a reasonable source of rancid odor.
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Hi,
Micro-contamination is 100% possible, but I suspect the oils, in this order:
1. Black seed oil: VERY prone to oxidation due to its high content of unsaturated fatty acids and volatile compounds; even the refined version can oxidize rapidly if not protected enough;
2. Shea butter: even the refined version can contain oxidized lipids, depending on processing/storage/handling;
3. Pomegranate sterols: if they contain residual unsaponifiables or are not fully deodorized, they could contribute to off-odors.
Ideally, you would perform some knockout experiments to find out the “culprit”.
If you don’t have time to do the said knockout experiments and want to keep the black seed oil, I would start by using a higher % of antioxidants (as obviously 0.1% is not working): either 0.15% tocopherols (0.05% in the oil phase, and 0.1% in the cool-down), or 0.05% tocopherols+ 0.05% rosemary extract+ 0.05% ascorbyl palmitate. Of course you could go higher/lower with the second suggestion, but you have no way to know, other than experimenting.
Different antioxidants work through different mechanisms, and combining them can lead to a synergistic effect (the overall antioxidant capacity is greater than the sum of individual antioxidants).
Also you said you are performing stability tests: it’s curious to me that the rancid smell did not come up after you exposed your emulsion to repeated cycles of high and low temperature, and it developed after one month.
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This reply was modified 1 day, 10 hours ago by Aniela.
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Agreed. As you used the term ‘rancid’, a term that in cosmetics typically gets applied to oils…. this makes sense. Most people starting out buy just hideous grade oils. Once an oil is deemed unusable by the industry due to degradation….it is NOT thrown away…but sold to the repackers. Many of my peeps have told me that they receive rancid oils from the repackers….the day it arrives.
If you are not using something like ICSC out of Denmark…then your lipids will always be ‘suspect’ unless you are testing them.
As with any cosmetic….. do a ‘knock-out’ test. Make a small batch …. each time removing one of the listed ingredients….and bingo…. pretty soon you will know what is causing it. 😉 If not one of the lipids…. then keep working through the list…with the most plausible candidates first.
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Next thing I would knock out….would be the ….’rich in Sulfur’ Irish moss. 🤣
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This reply was modified 1 day, 1 hour ago by Graillotion.
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This reply was modified 1 day, 1 hour ago by
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This reply was modified 1 day, 10 hours ago by
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