An innovative challenge test for solid cosmetics using freeze-dried microorganisms and electrical methods

• We studied new approaches for preservative efficacy test (PET).
• Freeze-dried microorganisms provide less variability of PET results.
• Results from electrical methods were equivalent to those by pour plate technique.

Freeze-dried bacteria and fungi were used as inoculum in 28 days' PET. An electrical method was used in replacement of the conventional plate count method. The use of freeze-dried microorganisms in association with the electrical method can minimize the workload and the variability involved in PET for cosmetic powders.