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Preservatives- Liquid Formulations (Microemulsions)
I have been tasked to prepare an aerosol air freshener with fragrance oils. The company has been using for years potassium citrate as a preservative. I did my homework and discovered that it is not effective against microorganisms. I confirmed that when I sent products that we stores as shelf life to microorganisms analysis. I found fermenting and non-fermenting bacteria on it.
Our EU consultant suggested me to use phenoxyethanol. Then, I am currently testing it on my formula at 0.5% wt, along with EDTA at 0.2% wt. My concern is that phenoxyethanol can be “inactivated” by non-ionic surfactant such as Tween 20 . Which I am using in my formulation at 1.05% wt.My question is, Am I really wasting time trying the phenoxyethanol in microemulsion containing Tween 20?
My alternative preservative is Methylisothiazolinone. I am planning on start with 0.1% wt. Any suggestions or comments?
Lastly, what’s your procedure to evaluate microorganism presence in your product? Do you send the out to analysis after a few months in stability test?
Thank you in advance for your help.Ericka.
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4 Replies
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I saw many commercial products with polysorbate 20 preserved with phenoxyethanol. I guess it might be dependent on quantities.
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Look up <USP 51> PET tests that should give you an idea of the industry standard of preservative challenge testing.Lots of resources out there on Water Activity and its relationship to microbial activity.If this is not going on skin you could always lower the pH below 3.5 and call it a day.Look into the pH environments for bacterial and fungal growth. I’m not going to quote the windows, but very low or very high pH is not friendly to microbes in general.
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I researched high end face mists. Most contain PEG-40 HCO or Polysorbate 20 and preserved with phenoxyethanol. What I noticed is that ethoxylated ingredient always goes after phenoxyethanol.
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