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help with lab testing
Hi, I made a serum for the face and used it for a month (pump bottle), then sent it to the lab for APC, yeast and mold testing. It came back with less than 1% of each. So I’m wondering what is my next step in order to get it to the market? Do I retest it in a few months or send it right away for a challenge test?
Any help with the guidelines for getting a product formulated then out to the market will be helpful!Thank you! -
21 Replies
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How many CFU’s?
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I thought CFU’s were the same as aerobic plate count APC? My guess is <1%
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I would contact Ben at Cosmetic Test Labs for guidance. He posts on this site under the name ‘The_Microbiologist’. You can also reach him at Cosmetic Test Labs Here is a link to thecompany’s website. They do all sorts of testing.
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You can do the challenge test (Preservative efficacy test) then do the 45°C stability study at least for 6 months and if passes the microbs (TVC & TFC both are < 10) then you can put into the market as per my knowledge. and m
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Hi love,
The results from an APC test should be expressed as “CFU/ml” or “CFU/g,” not as a percentage. I think there must be some confusion, either at your end or at the lab’s end. If you want, you can email me the report and I’ll check it out to see if I can make sense of it. If you’re interested, please email the main lab address (available on the website).
vjay is spot on. Do the challenge test to see if it can withstand microbial “insults,” then do stability to make sure it doesn’t undergo physical changes over time that could be off-putting, then make batches of the product and make sure that your APC counts are <10 (or some companies use <100).
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But 6 months???????
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Hi milliachemist,
Good point about the duration of the stability study. What would you recommend as a “default” time and temperature?
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But isn’t that too long a time keeping in view all the launch pressures and all? I mean when you say 45C, that means the study is being done at elevated temperature and which generally would be above normal, so is it not possible to shorten the time or 6 month study is considered as the standard period?
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Hi milliachemist,
At our lab we usually do 10 weeks @ 45C and call that roughly equivalent to one year at room temp.
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Thanks, that takes the load off, otherwise I would feel guilty about my testing
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Great feedback, all, just what I was looking for. Thank you! To clarify the APC count is based on CFU/gram and it came back <1. I like the 10 week @ 45C better, much shorter of a process. I’ll be in touch Microbiologist.
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Whether or not 6 months is too long depends on how confident you are with the stability of your product and how much risk you are willing to take. In some places it would be considered too short.
The practice I’m used too is 3 months stability for launch with a two year shelf life, when you get the 6 month results you can reevaluate the shelf life.
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Most places I’ve worked at with a time crunch for launch run three more or less separate stability tracks:
1) 45C for 10-12 weeks2) 40C for 6 months3) RT and refrigerator/freezer for two to three yearsObviously, almost no one would wait until 3 years passed, or even six months. It’s all about managing risk - passing 45C for 10 weeks is assumed to be roughly equivalent to two years at RT, so launch is allowed to go forward after 10 weeks of 45C stability, because the risk of failure is judged to be sufficiently low at that point.BUT…the stability testing continues, because the risk of failure, while small, still exists, and a stability failure can raise a red flag right up to launch time (and sometimes afterwards). -
Our stability test decisions were made after 8 weeks for formulas in which just the fragrance was changed. 12 weeks was always the official decision on pass/fail. Storage temp was 4C, RT, 37C, 45C
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We do 12 weeks too (4°C, RT, 25°C, 45°C, sun light). And 4°C and RT are kept for 3 years.
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Just curious, how is RT different than 25 C?
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Often taken to be 20°C , but in this case RT = ambient (i.e. uncontrolled temperature)?
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@Perry : RT is variable (my lab is in the production building and the temperature can go from 6°C to 30°C… 25°C is for the pH.
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Interesting. Our RT was always 25C +/- 2C
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I run stability more like Ayla does.
In my book, RT is semi-controlled room temperature, i.e. whatever the temp is on the storage shelves in the lab, which is set to be 70F/21C, but in practice fluctuates between 61F/16C and 77F/25C, depending on the time of year.
77F/25C stability is in an incubator, and it’s a much more stable environment. -
For emulsions you could also centrifuge it at ~5000 RPM’s for 3-5 minutes to get a quick idea of how well the emulsion has formed and how well it will hold up in stability testing.
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