Road trip essentials: Solid scrub bars, Neha asks: Can I use sodium benzoate as a preservative in emulsifying sugar scrub? My local vendor is unable to understand optiphen. Or can you help me with any other name for this preservative?
If you want to know more about preservatives, the first thing to do is consult the preservatives section of this blog. In that section, you'll notice I have general information about what we find in preservatives, a list of preservatives we can buy by name, and a downloadable chart, amongst other things.
If you click on "organic acids" - which I get might not be an obvious place to look - or search for "sodium benzoate", you'll reach this post on the topic. And here's what I wrote about it...
Sodium benzoate is bacteriostatic, which means it limits the growth of bacteria by messing with its metabolism, but doesn't kill it. It is also a recognized fungicidal ingredient.
The main problem in using sodium benzoate in our products is the pH level - sodium benzoate works best at pH 5 or less (possibly 6 or less), which means its use is limited to products more acidic products like toners or moisturizers with AHA or salicylic acid. You definitely want to own a pH meter if you're using this as your main preservative! Sodium benzoate is approved for us at up to 0.1% for food products and up to 1.0% for cosmetic and medicinal products. You don't want to use this with Vitamin C as studies have shown that together they can form benzene, which is carcinogenic. Geogard Ultra contains sodium benzoate as its preservative.
Reading this, does it seem like a good choice for an emulsified sugar scrub? No, because it isn't a broad spectrum preservative. (A broad spectrum preservative is one that kills off bacteria, mould, yeast, and other fungi. The preservatives we buy are called synergistic preservatives, which are combinations of preservatives intended to eliminate all the various contaminants we could see in our products.) We want something that protects us from all kinds of contamination, not just one or two types.
The other reason is that an emulsified sugar scrub is not acidic enough. Its pH is definitely above 5, which means sodium benzoate won't work well.
Optiphen a good choice? Again, check out the post I've written about it, then the update post on the topic as it relates specifically to scrubs. Optiphen isn't a broad spectrum or complete preservative as it doesn't contain a fungicide, so you'd have to combine it with something else.
A quick aside: If you want to know what's in Optiphen, look at the INCI name. It contains Phenoxyethanol (and) Caprylyl Glycol. If another company is making Optiphen under a different brand name - we see this all the time for surfactants - the INCI name will be the same, and you can buy that instead.
To summarize: In an emulsified sugar scrub, you can't use sodium benzoate or Optiphen as they aren't broad spectrum preservatives. If your supplier doesn't know the name of what you're asking for, refer to the INCI name as that should be the same around the world.
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