Hi
I have a general question about incorporating water soluble preservatives into Water-in-Oil emulsions.
When adding a preservative to a water in oil emulsion, does it matter if I add it to the water phase before homogenization, or to the final w/o emulsion afterwards? I would think it might be difficult to properly introduce and integrate the preservative after homogenization, seeing as the water droplets are almost hidden inside the continuous oil phase. Assuming the preservative is not damaged by the heat and pH of the process before homogenization and cooldown. Thanks
Hello,
The role of the preservative is to protect your product against oxidation, especially during the preparation of the emulsion.
Personally I would put it in the water phase, before homogenization.
Phil Geis So the article seemed to confirm my general suspicion, although there wasn't much ellaboration on the techniques ( https://library.scconline.org/v053n01/60 ).
It would appear that properly integrating the preservative into a water-in-oil/silicone emulsion requires it to be added to the water phase, prior to homogenization, but also making sure that the microbes in the Challenge Test are properly exposed to the water phase during "incubation". This is particularly relevant with regards to Aspegillus Brasiliensis, which can survive in spore-form when not "exposed" to the water phase at the beginning of the Challenge Test, and only germinating after a sample is taken to count CFU.
Glad you could get the article. Think one take away is that the challenge test has limited significance. Water droplets (with preservative) from formulation will be limited in encountering droplets of inoculum or from in-use contamination. In this context, preservation is largely to control manufacturing risks.
You can add the preservatives to the water phase and heat, then mix the oil phase in water phase
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