Home Cosmetic Science Talk General Science Is an incubator necessary for microbial testing?

  • Is an incubator necessary for microbial testing?

    Posted by Anonymous on July 7, 2016 at 1:43 pm

    Hello, I would like to purchase a microbial testing kit to test a few of my products, but the instructions require incubating at 35C for a day for bacteria and at 30C for 2 days for fungi. Is an incubator a necessity with these kits? Can an alternative be used - an oven or even leaving out at room temperature for a longer amount of time (I live in the tropics; it is 30C right now at 9pm at night) - or is precision regarding temperature and timing required for accurate results? Thanks.

    manuksh replied 6 years, 7 months ago 8 Members · 14 Replies
  • 14 Replies
  • bobzchemist

    July 7, 2016 at 2:18 pm

    If you are going to sell or even give this product to other people, precision is critically important - the risk of getting a false negative is much too high. If you’re just making products for yourself, the risk level is up to you.

  • oldperry

    July 7, 2016 at 2:32 pm

    Sacrificing product safety to save a little money up front doesn’t seem like a good idea. 

  • David

    July 7, 2016 at 6:28 pm

    If you can record the temperature 24/7 it would be good enough. However, it is easier to buy an incubator. I don’t live in the tropics….. but maybe you should also check that the temperature doesn’t go to high?

  • bill_toge

    July 7, 2016 at 7:33 pm

    @Perry there are quite a few companies out there who didn’t get that memo!

  • Anonymous

    July 8, 2016 at 7:04 am

    Check Product twice or thrice that it won’t affect anyone and safe for all. it was not costly to buy an incubator so buy it.

  • tanelise

    June 14, 2017 at 7:47 pm

    I know this is an old discussion but can someone make a recommendation as to where one can purchase an incubator? I’m setting up a lab in my home. Thank you!

  • markbroussard

    June 14, 2017 at 7:55 pm


    You can purchase a small incubator from Schuelke & Mayr for use with their microbial test strips … costs about $300 to $400.

  • tanelise

    June 14, 2017 at 9:48 pm

    Thanks Mark!

  • mikethair

    June 15, 2017 at 3:54 am

    As mentioned by @MarkBroussard   “You can purchase a small incubator from Schuelke & Mayr for use with their microbial test strips”….. exactly what we have done in our productio  facility. We use the microbial test strips for monitoring of low risk products (just to be 100% sure).

  • tanelise

    July 2, 2017 at 2:06 pm

    Mark’s tip led me to eBay where I found one used for $105. Here’s one for $115:


    I get my dip slides from Biosan Laboratories. A box of 10 is $49.99. Seems expensive but not sure.


    They also have incubators upwards of 400.00

    Good luck

  • manuksh

    July 4, 2017 at 1:16 pm

    As I understand the question was about the temperature  precision requirements during the test period. For example: what if someone put the test pod into a sterile place where the temperature varies 20C-30C and keep it 3 days instead of  2? Will this work or the tolerance of +-2C is mandatory?

  • mikethair

    July 4, 2017 at 9:58 pm

    You are correct @manuksh about the original question. My approach to this issue is one of compliance and customer safety. If I am facing a GMP inspector, and taking customer safety seriously, the safest route is to follow the manufacturers instructions for the test kit. It would be a weak argument on our side if we didn’t in the case of facing a customer compalint or GMP query. 

  • manuksh

    July 7, 2017 at 10:52 am

    I could not find the right answer, but I can link what FDA says for Conventional Plate Count Method :

  • manuksh

    July 10, 2017 at 7:59 am

    I am confused. So I guess the incubator temperature control high precision is not critical. See what is written in microbiological agar test kit user manual: 25-30C +/- 2C is confusing statement!  

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