Temperature to pour plates

Paul A. Vescio vescip at rpi.edu
Thu Feb 9 16:40:26 EST 1995

In Article <3hdnig$6rr at post.its.mcw.edu>, ckrepel at post.its.mcw.edu (Candace
Krepel) wrote:
>: WmsFan (wmsfan at aol.com) wrote:
>: : Here's an easy one for you microbiologists. My son is doing a simple
>: : science experiment looking at the effect of temperature on growth rates of
>: : bacteria in milk. We got some sterile agar and plates from a local
>: : company. We melted the agar, added milk to the plates with sterile
>: : pipettes, and are about to pour the media....but I imagine we could
>: : sterilize the milk if we pour the agar too hot. What temperature should we
>: : cool the agar to before we pour it?

Agar solidifies below 60C. We do a very similar experiment in the Micro lab
at RPI. If you pour the plates to hot it will curdle the milk when added
probably affecting alot of the microbes also, although I suspect any
lactobacillus present are fairly heat resistant.  A good general rule that
we teach micro students is that if the agar is cool enough to hold against
your cheek (sensitive skin) comfortably then it is cool enough to add
bacteria or in this case Milk. 
Paul A. Vescio
Biology Dept.
Rensselaer Polytechnic Institute

!!New York Rangers  Stanley Cup Champions 1994!!

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