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Offlinelibertaire
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At what temperature do contaminant spores die?
    #11563238 - 12/01/09 04:44 PM (4 years, 8 months ago)

I've searched high and low for the answer to this.  Does anyone know the specific temperature at which all living things that would potentially contaminate a substrate are destroyed?  I know steam sterilization gets up to 212*F and Pressure Cookers get up to 250*, so I would imagine that the temperature is somewhere between those two numbers.  Does anyone know?


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Invisibleinski
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Re: At what temperature do contaminant spores die? [Re: libertaire]
    #11564286 - 12/01/09 07:07 PM (4 years, 8 months ago)

Different fungi and bacteria spores die at varying temperatures, some bacterial endospores can survive quite high temperatures, sorry I can't be more specific than that!
inski.


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OfflineRogerRabbitM
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Re: At what temperature do contaminant spores die? [Re: inski]
    #11564967 - 12/01/09 08:37 PM (4 years, 8 months ago)

You'll often hear 20 minutes at 121C as the magic number, but in my experience, that's open to debate.  Fungi spores are generally recognized to be killed by a temperature of 140f/60c for an hour.
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Offlinelibertaire
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Re: At what temperature do contaminant spores die? [Re: RogerRabbit]
    #11568457 - 12/02/09 10:00 AM (4 years, 8 months ago)

Ok, so pressure cookers get to 250*F for a reason.  I have more questions to ask in a similar vein, but I'll refrain from asking them for fear of being ridiculed.  Thanks for your help.


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Offlinesolumvita
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Re: At what temperature do contaminant spores die? [Re: libertaire]
    #11568787 - 12/02/09 11:32 AM (4 years, 8 months ago)

121 degrees is the accepted norm temperature for sterilization and that is because there are some bacteria which can survive up to 120 degrees. 

And before some wise ass comes along about hyperthermophiles  remember that the question was in the substrate.


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InvisiblePinback
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Re: At what temperature do contaminant spores die? [Re: libertaire]
    #11576839 - 12/03/09 03:32 PM (4 years, 8 months ago)

There is a common way of measuring this which is called Thermal Death Time. It is defined by how long it takes to kill 90% of the organisms at a certain temperature. The higher the temperature, the shorter the time. There is also a way of describing the effect of increased temperature on the time, but I don't recall the specifics. The Thermal Death Time is different for different organisms.

An example to clarify:
Assume the TDT for a certain bacterium is 1 minute at 121 °C, and you have 1000 of those bacteria in your jars.
After 1 minute at 121 °C, you have killed 900 of them (90%).
After 2 minutes, you have killed 990 (99%) of them.
After 3 minutes, you have killed 999 of them and have one left (on average).
After 4 minutes, you have on average 1 bacterium in every tenth jar.
After 5 minutes, you have on average 1 bacterium in every 100th jar. And so on.

tl;dr: There is no specific temperature at which contaminants die, it has to do with time as well.


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Invisiblemycoelf
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Re: At what temperature do contaminant spores die? [Re: Pinback]
    #11596958 - 12/06/09 05:26 PM (4 years, 8 months ago)

Don't forget to factor in relative thermal mass and head room for each container. AS an example For wood-lovers 6 five pound SAB's enriched 300 g dry grain and between 38 and 50% moisture, I go 4 hours at 15 psi. I have gotten by with 3, and there is a point in which you could over cook a substrate lending to a compromised suitability for colonization.

There is a good discussion of these factors of play in GGMM, but a specific solution requires a context of a specific spawn run plan. I have found the documenting each variable in every attempt leads to a valuable source of DATA allowing me to isolate problems experienced in failure. I then am well tooled to hunt down and kill the errors in technique or apparatus. Dialing in a strain requires months of research, but there is no greater reward than to achieve a good set of formula. The practice of consistency will lead to this success.

I used to run 18 1/2 pint widemouth PF tec jars with brown rice and vermic and get by with 30 min at 15psi. Then I got a 1941 PC and put 52 of the same for 30 min and got a 60% fail rate, I went then for 45 min and found a lesser rate of failure, ultimately I settled on 1 hour and found no problems with Success rate.

good luck


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Offlinelibertaire
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Re: At what temperature do contaminant spores die? [Re: mycoelf]
    #11599401 - 12/06/09 11:17 PM (4 years, 8 months ago)

So it's not so much of an issue of how much, but how much for how long.  Interesting.  Thanks for all of you help everyone, very useful information all around.


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