The two variants of the preservative efficacy test differ in some aspects of the methods and assessment criteria. For implementation according to ISO 11930, the following applies:

• the microbial status of the product must be checked before implementation
• Escherichia coli is required as an additional test organism
• a different nutrient medium (Potato Dextrose Agar) is prescribed for Aspergillus brasiliensis
• the procedures for preparing the microorganism cultures are newly regulated
• there are no requirements for microbial reduction after 2 days
• there are different requirements for the yeast Candida albicans and the mold Aspergillus brasiliensis
• a margin of 0.5 log levels is permissible to account for measurement uncertainty
• Criterion A and B no longer have the same significance

Further information on the two types of challenge tests can be found in the BAV Newsletter Cosmetics Part 3 (available at https://www.bav-institut.de/files/newsletters/Sondernewsletter-Kosmetik-Teil-3-in-2013.pdf ).