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uninc4life2010
Unincorporated



Registered: 06/05/10
Posts: 1,124
Last seen: 7 months, 12 days
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Can someone explain pasteurization a little better to me?
#22073305 - 08/10/15 07:40 PM (8 years, 5 months ago) |
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I understand the process, I've done it several time myself with little issues. 140-160 F for 60 minutes, blah, blah, blah... What I'm not quite understanding is the science behind it. From what I have been told, proper bulk pasteurization will reach temperatures sufficient to kill all of the mold spores in your substrate, but will leave behind bacteria that will help keep it from contaminating for roughly two weeks. I don't understand how "bad" bacteria dies and "good' bacteria lives, and I don't understand how the bacteria that is left over doesn't out compete the mycelium and contaminate the substrate.
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Pastywhyte
Say hello to my little friend



Registered: 09/15/12
Posts: 37,810
Loc: Canada
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Re: Can someone explain pasteurization a little better to me? [Re: uninc4life2010]
#22073333 - 08/10/15 07:46 PM (8 years, 5 months ago) |
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The bad bacteria dies at lower temps. Most of the time cubes can out muscle most bacteria anyway, in fact most people have bacterial spawn and never even know it. They still often see a flush or two. In this case there is only a very small amount of bacteria left, and its just enough to give you a window to colonize in.
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cronicr



Registered: 08/07/11
Posts: 61,436
Loc: Van Isle
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Re: Can someone explain pasteurization a little better to me? [Re: Pastywhyte]
#22073350 - 08/10/15 07:48 PM (8 years, 5 months ago) |
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its' thermophyllic bacteria that survives and once it starts to cool spreads throughout the substrate
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  It doesn't matter what i think of you...all that matters is clean spawn I'm tired do me a favor
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blindingleaf
blue collar underworld


Registered: 07/19/13
Posts: 22,008
Loc: sub-surface unseen
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Re: Can someone explain pasteurization a little better to me? [Re: cronicr]
#22073387 - 08/10/15 07:55 PM (8 years, 5 months ago) |
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Quote:
I don't understand how "bad" bacteria dies and "good' bacteria lives, and I don't understand how the bacteria that is left over doesn't out compete the mycelium and contaminate the substrate.
welcome to the billion dollar industry of button growing
-------------------- A few thoughts on cultivation MICROBIAL HUSBANDRY!!!! The whole is greater than the sum of its parts
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Toadstool5
A Registered Mycophile



Registered: 01/22/15
Posts: 1,359
Loc: The Golden State
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Re: Can someone explain pasteurization a little better to me? [Re: blindingleaf]
#22073418 - 08/10/15 08:00 PM (8 years, 5 months ago) |
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Quote:
welcome to the billion dollar industry of button growing
soooooo true! They fine tune their subs/casings like no other.
-------------------- If you do not know where the mushroom products you are consuming are grown, think twice before eating them. - Paul Stamets AMU Teks Stro's Write Ups
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bluegill
intergalactic toejam



Registered: 11/05/13
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Re: Can someone explain pasteurization a little better to me? [Re: Toadstool5]
#22073504 - 08/10/15 08:13 PM (8 years, 5 months ago) |
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-------------------- "Psychedelics are like carnival tickets, you buy the ticket and take the ride, then you get off and go home. What your talking about is physical death. That's when you're pulled into the carnival against your will and your stuck there for eternity."
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Kizzle
Misanthrope


Registered: 08/30/11
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Re: Can someone explain pasteurization a little better to me? [Re: bluegill]
#22074173 - 08/10/15 10:36 PM (8 years, 5 months ago) |
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Quote:
I don't understand how the bacteria that is left over doesn't out compete the mycelium and contaminate the substrate.
Because the substrate is optimized for the growth of mushroom mycelium. The readily available nutrients the bacteria needs to reproduce are limited so the bacterial population is also limited. Of course they're even more limited after the bacteria consumes them, leaving behind little for mold spores to use to germinate.
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ShroominMe
Stranger

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Re: Can someone explain pasteurization a little better to me? [Re: Kizzle]
#22074442 - 08/10/15 11:48 PM (8 years, 5 months ago) |
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It's great to understand the 'science behind it' but even more important to find a reliable tek and follow it.
Your eyes and experience can be more reliable than your brain, my friend 
(BTW I'm sure your brain hates this comment!)
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uninc4life2010
Unincorporated



Registered: 06/05/10
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Last seen: 7 months, 12 days
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Re: Can someone explain pasteurization a little better to me? [Re: Kizzle]
#22074443 - 08/10/15 11:48 PM (8 years, 5 months ago) |
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Quote:
Kizzle said:
Quote:
I don't understand how the bacteria that is left over doesn't out compete the mycelium and contaminate the substrate.
Because the substrate is optimized for the growth of mushroom mycelium. The readily available nutrients the bacteria needs to reproduce are limited so the bacterial population is also limited. Of course they're even more limited after the bacteria consumes them, leaving behind little for mold spores to use to germinate.
If that's the case, why not just sterilize the substrate? Whatever is left over in the sub after heat pasteurization must provide some benefit to the growth of the mycelium. Are you saying that the remaining bacteria use up whatever any other organisms might use to survive?
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cronicr



Registered: 08/07/11
Posts: 61,436
Loc: Van Isle
Last seen: 2 years, 8 days
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Re: Can someone explain pasteurization a little better to me? [Re: uninc4life2010]
#22074506 - 08/11/15 12:13 AM (8 years, 5 months ago) |
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you can sterilize bulk if you keep the conditions sterile as well in filter patch bags but in open air there are no beneficial bacteria to help fend off contams and you will likely get mold
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  It doesn't matter what i think of you...all that matters is clean spawn I'm tired do me a favor
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Alkaloids
3,4,5-trimethoxyphenethylamine



Registered: 11/15/98
Posts: 743
Loc: pubis mons
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Re: Can someone explain pasteurization a little better to me? [Re: uninc4life2010]
#22074572 - 08/11/15 12:54 AM (8 years, 5 months ago) |
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All good questions uninc4life2010.
I'll attempt a useful answer.
The bacteria issue is, i think for several reason, a bit of a mis-direction. Most bacteria and most fungal mycelia do not tend to favor the same conditions for growth. By keeping substrate moisture levels in a healthy range for fungus you automatically select against bacteria. They want more moisture in their swimming pool. Another key item that is kind of concurrent with the moisture levels is minimizing those readily available starches and sugars that bacteria love so much. Tacky grain? You're gonna have a bad time.
Certainly pasteurization seems to select against the less hardy, thankfully, human pathogens and that gives us a step up for ourselves, but if the substrate had human pathogens in it that wouldn't bother the mushrooms generally. Plenty of experience from lots of growers that can attest to the help that pasteurization can provide for contaminated substrates.
Can't remember who said it, but most people are likely to have some bacteria and yeasts either in their final substrate and/or their starting cultures. Hence the effectiveness of heavy spawn rates. It's to outrace the potential competitors by sheer inundation.
The use of the term sterilization should be adjusted so that it is used more in line with it's proper meaning. We either do low temp or high temp pasteurization with the high temp killing a larger proportion of non-desired micro organisms. It is so unlikely to achieve actual sterilization working with complex organic substrates that is compels me to change my terminology. 
0.000000000000000000002
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Kizzle
Misanthrope


Registered: 08/30/11
Posts: 9,855
Last seen: 16 hours, 23 minutes
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Re: Can someone explain pasteurization a little better to me? [Re: uninc4life2010]
#22074668 - 08/11/15 02:00 AM (8 years, 5 months ago) |
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Quote:
uninc4life2010 said:
Quote:
Kizzle said:
Quote:
I don't understand how the bacteria that is left over doesn't out compete the mycelium and contaminate the substrate.
Because the substrate is optimized for the growth of mushroom mycelium. The readily available nutrients the bacteria needs to reproduce are limited so the bacterial population is also limited. Of course they're even more limited after the bacteria consumes them, leaving behind little for mold spores to use to germinate.
If that's the case, why not just sterilize the substrate? Whatever is left over in the sub after heat pasteurization must provide some benefit to the growth of the mycelium. Are you saying that the remaining bacteria use up whatever any other organisms might use to survive?
Basically. That's not counting nutrients that the mycelium is freeing as it degrades lignocellulose which gives the spawned mycelium a huge advantage as few competitors are able to obtain nutrients in that way and those that can usually still need readily available nutrients to germinate and become established. The nutrients the bacteria ingest become unavailable to contaminants.
That's only part of it. The bacteria also produce metabolites that can antagonize growth of some species of mold. Trichoderma grows well on sterilized substrate but has trouble becoming established on substrates that haven't been heat treated. Pasteurization is a way of gaining the benefits of a heat treated substrate, like increased yield, while maintaining a resistance to Trichoderma and reducing the number of various contaminant spores already present.
You can see here the Trich mycelium is unable to colonize near the Bacillus colonies.
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Edited by Kizzle (08/11/15 02:05 AM)
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Legitimate_itch
Coloniser


Registered: 01/07/14
Posts: 103
Last seen: 7 months, 10 days
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Re: Can someone explain pasteurization a little better to me? [Re: Kizzle]
#22074724 - 08/11/15 02:42 AM (8 years, 5 months ago) |
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Wow, neat !
-------------------- This is psychic martial arts
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