Optiphen Plus is a liquid broad spectrum preservative with an INCI of Phenoxyethanol (and) Caprylyl Glycol (and) Sorbic Acid. (It differs slightly from Optiphen with the inclusion of the sorbic acid.) As it isn't heat sensitive, we can include it in our water based creations at 80˚C or lower in the water phase of our process. It is not a formaldehyde donor.
We know phenoxyethanol is a good bacteria and yeast killer, while caprylyl glycol is a good bacteriostatic and bactericide, so why include sorbic acid?
Sorbic acid is one of the organic acids, and it can be found paired with a calcium, magnesium, or sodium salt to help increase its solubility. It's a good fungal, mould, and yeast inhibitor at pH 6.0 or less, and it's an okay bactericide. It's generally found in food stuffs at 0.01% to 0.1%.
By combining these three preservatives, we have a great bacteria, yeast, mould, and fungal killing combination suitable for water containing products. I'm not sure if this version of Optiphen can curdle or destabilize your emulsions as I've never used it, so please report on your experiences in the comments!
The one down side of using Optiphen Plus is the limited pH range of the product. It works best at pH 6.0 or lower, which means you will need to test your products to ensure they are in the right range. For instance, if you're using decyl glucoside with a pH that can range from 7.5 to 11 as your primary surfactant, you'll need to get that pH down substantially to play well with Optiphen Plus.
Summary of Optiphen Plus
INCI: Phenoxyethanol (and) Caprylyl Glycol (and) Sorbic Acid
Usage at 0.75% to 1.5% in the heated water phase of your product.
Not suitable for anhydrous products.
Good for products with a pH of 6.0 or under
For the data sheet, click here.