Challenge and Stability Testing - Formulator or 3rd Party?

Generally, is it considered a best practice to contract with a separate independent third party lab to conduct microbiological challenge and stability testing instead of having the contract formulator, who is doing the actual formulating, test their own prototypes?

In other words, do contract formulators generally conduct their own challenge and stability testing of the protypes they formulate for clients with their own thermo microbiological incubator equipment or are prototypes generally sent to third party labs to ensure independence in testing? 

Any responses or discussion about the entities generally involved with the logistics of microbiological challenge and stability testing of contract formulator-created prototype products is greatly appreciated.  Thanks!


  • PerryPerry Administrator, Professional Chemist
    Big and medium sized companies do their own stability and micro challenge testing. They have a specific protocol written out and made available to inspectors if required.  So, you can do your own stability testing. But it requires a big up-front investment in ovens and light chambers and protocol writing and following.  That's why it's typically less expensive and easier for a smaller company to outsource.
  • I agree with Perry. In our case, we conduct stability testing ourselves (micro test included). As for the challenge test, we also seek for assitance from our suppliers. Some of them are free of charge, some are not.
  • Hello,

    I'm new to the field/forum and looking for in house micro tests. We have the slides but I was looking for something that had a shorter incubation time than 48 hours. I've searched for them but am not finding anything. 

    Also, for a company based in the US, there are not actual guidelines on what you have to micro test for correct? We could just test for Total Plate count and that be sufficient if we have decided so?


  • We have a simple freezer and an incubator ($300 or so, small) that we use for freeze/thaw and heat stability (40c, 50c, etc.)

    I'd also love to get into in-house challenge testing. Anyone with ideas on how we can begin would be great. Thanks!
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