Microbiological safety testing

The regulation itself didn’t specify the test procedure for the challenge test. Beside the test from the EU and US pharmacopoeia in-house test protocols are established since many years. The applicability of the schülke KoKo test for the evaluation of the microbiological safety of finished cosmetic products is assessed in the paper: Evaluation of the Microbiological Safety of Finished Cosmetic Products 

Demands for challenge testing are specified only in the SCCS notes of guidance . In paragraph 4-4 “Guidelines on Microbiological of the Finished Cosmetic Product“ in the 8th revision (December 2012) of the SCCS publication “Notes of Guidance for the Testing of Cosmetic Ingredients and their Safety Evaluation” is an obligation for carrying out a preservation test with all cosmetic products which could be contaminated under normal storage and usage conditions or if an infection risk for the consumer exists.

This information shall be indicated by the symbol and the period itself in months and/or years. For products with a minimum durability of more than 30 months, it is not allowed to indicate the minimum durability instead of the “Period after Opening”.  

A variety of relevant methods may be used to support the period indicated on a product, including those used during product development, since there is no officially sanctioned methodology that could be used. Examples of sources of information for assessing a product’s PaO may include:
• microbiological challenge tests
• stability data - analytical data (e.g. preservative analysis)
• type of packaging - experience with similar formulations and products
• consumer habits and practices

Source: Practical implementation of Article 6(1)(c) of the Cosmetics Directive (76/768/EEC) - LABELLING OF PRODUCT DURABILITY: “PERIOD OF TIME AFTER OPENING”

The inoculum contains pathogenic microorganisms as gems which are well known for product spoilage. All species have to be cultivated separately and mixed directly before the addition, to ensure a constant composition and germ count of the inoculum. Its germ count is approximately 10^7-8 cfu/ml, which means a germ count of approximately 10⁶ cfu/ml in the sample.
A sample can be called well preserved, if it passes a period of six weeks under the above described laboratory conditions without showing microbial growth on the test batches. That means even after the sixth inoculation no microbial growth can be observed. From many years of experience in the use of this test method these results can state the microbiological stability of 30 months which is recommended for cosmetic products.

Compared to other methods ISO 11930 is an overall standard to evaluate the antimicrobial stabilisation of a cosmetic product. With the decision diagram in Annex A also formulations intrinsically hostile to microbial growth, specific manufacturing conditions, packaging and/or conditions for use and the reference to ISO 29261 (Guidelines for the risk assessment and identification of microbiologically low-risk products) are covered.

schülke prepared a comparison of ISO 11930 and different established methods in the market and run comparative tests for ISO 11930, Ph. Eur. 7 and the schülke KoKo Test.