Sunday, October 17, 2010
Preservatives: How the heck do they work?
Preservatives inactivate the microorganisms in our products in a few different ways, but the primary way is to cause them cause some kind of chemical disruption that leads to death. They leak their internal fluids, they can't maintain pH, their cell walls break open, and so on.
But once the preservative has been used to attack a little beastie, it's used up and can't fight anything else. This is one of the reasons we need to preserve our products at a proper level and why we want to start with as little contamination as possible in our workshop, our ingredients, our equipment, and our packaging!
Preservatives tend to live in the water phase of our products to fight any contamination that might show up in our creations because that's where the beasties live. (They can migrate into the oil phase to fight beasties there, but most our problems are in the water phase!)
We can improve the efficacy of our preservatives by adding propylene glycol, ethanol (alcohol), or glycerine - not only do we get the lovely hygroscopic properties of one of these humectants, but we improve their evil fighting powers! (I do love my double duty ingredients!) Adding a chelating ingredient like citric acid or EDTA to quaterniums, parabens, phenolics, sorbic acid and imidazolidinyl urea also boosts their beastie fighting power!
And there are some ingredients that will interfere with preservatives or inactivate them completely. I'll be writing more about this in the near future, but non-ionic surfactants like polysorbate 80, pigments like ultramarine blue, and thickeners like cellulose derivatives and guar gum are the top ingredients that might interfere with your preservatives! Each preservative type has something that interferes with it and something that can boost it, and it's valuable to know what affects what!
The ideal preservative will be a broad spectrum preservative, meaning it 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.
If you take a look at something like Phenonip (INCI: phenoxyethanol, methylparaben, butylparaben, ethylparaben, and propylparaben), you'll see more than one preserving ingredient in the mix. Parabens don't tend to be very good individually, but in combination you've got yourself an awesome broad spectrum preservative.
Join me tomorrow as we take a look at the various chemicals we find in our preservatives!