I'm looking for some feedback from anyone well versed in acidified filing. I will lay out our current situation below:
We produce an oil in water dispersion. When performing the challenge study for the product, our Process Authority wanted only the water phase of the product to challenge. The pH of the water phase was ~3.50. The finished product pH is ~3.8 when the oil phase is added. I filed the process with the challenge study and listed our equilibrium pH at 4.0 (spec is 3.8 plus/minus 0.2). We received an inquiry from the FDA stating that the product could not be filed at a pH higher than that of the control used in the challenge, which makes complete sense. The Process Authority stated at the time of the challenge that the water phase is the phase of microbiological concern, therefore that is all that should be challenged. The issue lies in the pH difference once the oil phase is added. Our Process Authority has offered to write a letter explaining the unique situation of the product to respond to FDA with. I see 3 potential pathways:
1.) Submit the letter from the Process Authority with our own cover letter.
2.) File at pH of 3.5 and measure/prove the the water phase pH is 3.5 if challenged.
3.) Re-challenge the finished product with oil phase.
This product is set to be released to market very soon, we are in pilot plant trials. A challenge study would take 30 days minimum pushing that date back.
Any insight or opinions would be greatly, greatly appreciated. Thank you.