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bakedbeings
orbiter of truth


Registered: 09/01/20
Posts: 4,218
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap]
#28191012 - 02/17/23 05:20 AM (11 months, 4 days ago) |
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Quote:
Btw are there any physics experts out there who can explain why venting is necessary? The reasoning I've read has always been that the "atmosphere" must be released to make room for steam, but isn't steam just atmospheric gas that is saturated with water vapor? So if one were to not 'vent', wouldn't all the atmospheric gas in the PC eventually become saturated with water vapor and become steam? Or is it actually true that failure to vent means that steam cannot fully occupy the space in the chamber due to pockets of atmospheric gas?
steam conducts heat much better than air. venting allows the air to escape so the chamber can be filled with steam
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SirPsycho
Purple Belt in Google-Fu



Registered: 01/01/20
Posts: 6,901
Loc: Rent free in your head
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Re: Autoclave Validation and Load Penetration [Re: bakedbeings] 1
#28191176 - 02/17/23 08:19 AM (11 months, 4 days ago) |
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Not only does steam conduct heat better (higher heat transfer coefficient) than air it also has a much higher specific heat capacity than air so steam at 250F has a lot more energy stored than air at that same temp.
IIRC steam also has higher heat transfer coefficient than liquid water, like orders of magnitude higher
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Ask me about free Ps tampanesis, Ps subtropicalis and Ps cubensis (ESS) prints Balance in life is like running on ice.
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ReverendMyc

Registered: 03/29/19
Posts: 1,494
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Re: Autoclave Validation and Load Penetration [Re: SirPsycho] 1
#28191261 - 02/17/23 09:17 AM (11 months, 4 days ago) |
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Quote:
SirPsycho said: Not only does steam conduct heat better (higher heat transfer coefficient) than air it also has a much higher specific heat capacity than air so steam at 250F has a lot more energy stored than air at that same temp.
IIRC steam also has higher heat transfer coefficient than liquid water, like orders of magnitude higher
My thermogoddamnix classes were a long time ago, but that is how I learned it as well. Found this article that was a good refresher. It refers to steam systems such as engines and turbines, which is what I learned on, but the physics are the same.
-------------------- LAGM 2.024Stoned Gummys tek (Gummies from sclerotia or mushrooms) *Not just for stones any moreHow to succeed in mycology (and life) - know nothing, read everything, try something, and accept advice. Don't Panic   
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nakadash1
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Registered: 11/02/22
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Re: Autoclave Validation and Load Penetration [Re: ReverendMyc]
#28191515 - 02/17/23 11:52 AM (11 months, 4 days ago) |
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Thanks guys! I kind of get it - it sounds like the 10 minutes I'm trying to save by not venting is actually ending up costing more time so I guess that settles it
-------------------- #1 Tek With utmost care and precision,I work to achieve my fungal mission. Sterilizing all my tools and space,to ensure not a single spore is out of place. I carefully select the fungal strain and onto the agar, I make it rain. With a steady hand and gentle touch, I inoculate the plate without a hitch. Success is sweet when it's pure and true, and my agar plates are a testament too. A job well done, with no contamination, my fungi inoculation, a thing of admiration. JK NO --Bacteriological Virtuoso aka Master of Mold
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: Autoclave Validation and Load Penetration [Re: nakadash1] 1
#28191637 - 02/17/23 01:11 PM (11 months, 4 days ago) |
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Your pressure cooker will not reach the appropriate internal temperature without venting/purging the internal gases.
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Wintergirl
Student

Registered: 03/19/22
Posts: 104
Loc: Home Planet
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap] 1
#28191646 - 02/17/23 01:19 PM (11 months, 4 days ago) |
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And it never crossed my mind I had to vent the Instant Pot. But based on the discussion here I'm going back to the Presto anyway.
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SirPsycho
Purple Belt in Google-Fu



Registered: 01/01/20
Posts: 6,901
Loc: Rent free in your head
Last seen: 2 hours, 49 minutes
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Re: Autoclave Validation and Load Penetration [Re: nakadash1] 4
#28191682 - 02/17/23 01:44 PM (11 months, 4 days ago) |
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Quote:
nakadash1 said: Thanks guys! I kind of get it - it sounds like the 10 minutes I'm trying to save by not venting is actually ending up costing more time so I guess that settles it
That's generally how every way we try to save time in cult goes.
Growing mushrooms takes a couple of months, no point in trying to shave off a few minutes or even a day.
If you want speed focus on getting clean culture and proper prep of materials.
--------------------
Ask me about free Ps tampanesis, Ps subtropicalis and Ps cubensis (ESS) prints Balance in life is like running on ice.
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altford78
What do I put here

Registered: 05/09/23
Posts: 890
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap]
#28354081 - 06/10/23 06:07 AM (7 months, 15 days ago) |
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Sorry if this was discussed previously, couldn't find it.
Have you done validation with the BI inside an agar bottle or LC bottle?
I've seen you mention elsewhere that you do 45min @ 15psi for your liquids, while many other teks/people go for 15-20mins. Did you have a BI fail to validate at <45mins?
The quote you have in the OP from the research on pressure cookers says a minimum of 15mins, but they also have a 60mins minimum for a couple yeasts and penicillium (but their highest psi was 11.6 in the instant pot)
-------------------- Mold cultivator extraordinaire I also dabble in bacteria I'm also a retard sometimes
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: Autoclave Validation and Load Penetration [Re: altford78] 2
#28354125 - 06/10/23 06:56 AM (7 months, 15 days ago) |
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Quote:
altford78 said: Sorry if this was discussed previously, couldn't find it.
Have you done validation with the BI inside an agar bottle or LC bottle?
BI ampoules cannot be submerged in liquids, but liquids readily sterilize due to the conductivity of water. I won't cover the data regarding liquids due to the abundance of information already available across the internet.
Quote:
I've seen you mention elsewhere that you do 45min @ 15psi for your liquids, while many other teks/people go for 15-20mins. Did you have a BI fail to validate at <45mins?
I recommend 45 mins for liquids to ensure all powders have been thoroughly dissolved. Folks often complain about: clarity of agar or LC, sediment, reduced gelling strength, weak growth, and unknown sources of contamination. Instead of troubleshooting each problem individually, 45 mins @ 15psi covers every base by solving each problem with a single solution.
Quote:
The quote you have in the OP from the research on pressure cookers says a minimum of 15mins, but they also have a 60mins minimum for a couple yeasts and penicillium (but their highest psi was 11.6 in the instant pot)
Yes. If you're running a pressure cooker/autoclave that can reach 15psi, the minimum threshold for liquids is 15 mins; however, the minimum standard is a minimum. If you're the sort of person who strives for the minimum acceptable effort in life, no matter the endeavor, your results will reflect that effort. When running at lower temps/pressures, add time.
The minimum cycle for the pharmaceutical industry is a 30 minute cycle 12 log reduction. The first 15 minutes produces a log 6 reduction of CFUs from 106 to 0, and a further log 6 reduction during the final 15 mins to ensure a sterility assurance of 10-6.
30 mins is considered the minimum standard for public safety regarding colony forming units for pharma products. A single 6 log reduction (15 mins @ 15psi) could fail to produce sterile media if mistakes were made during the sterilization process. This is why more is more with sterility, there's too many variables to consider when dealing with microorganisms. Redundancy is key, mistakes happen. The best course of action with regards to microorganisms and their byproducts are extended exposures times, within reason. This is a very cheap insurance policy.
You'll find that I'm not alone when recommending extended purge and cycle times, including the 45 minute cycle for liquids. I know Pasty recommends the same, I'm sure others are do the same.
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altford78
What do I put here

Registered: 05/09/23
Posts: 890
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap]
#28354172 - 06/10/23 07:30 AM (7 months, 15 days ago) |
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Thanks man! I didn't know you couldn't use BI in liquids.
I usually do 20-25mins at 18psi, I'll start doing 45 like you do.
-------------------- Mold cultivator extraordinaire I also dabble in bacteria I'm also a retard sometimes
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: Autoclave Validation and Load Penetration [Re: altford78]
#28354177 - 06/10/23 07:35 AM (7 months, 15 days ago) |
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I'm actually not 100% sure if they can be submerged, now that I think of it. They have 3 little holes in the top which I assumed would cause a problem but, I'm not sure....
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altford78
What do I put here

Registered: 05/09/23
Posts: 890
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap]
#28354186 - 06/10/23 07:48 AM (7 months, 15 days ago) |
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maybe you can put them in a sterilization pouch? should be hermetic
-------------------- Mold cultivator extraordinaire I also dabble in bacteria I'm also a retard sometimes
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Pastywhyte
Say hello to my little friend



Registered: 09/15/12
Posts: 37,808
Loc: Canada
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Re: Autoclave Validation and Load Penetration [Re: altford78] 2
#28354918 - 06/10/23 08:42 PM (7 months, 14 days ago) |
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In the game of overkill more is more
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altford78
What do I put here

Registered: 05/09/23
Posts: 890
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Re: Autoclave Validation and Load Penetration [Re: Stipe-n Cap] 1
#28355167 - 06/11/23 03:36 AM (7 months, 14 days ago) |
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I found this table which confirms pretty much your 45min cycle time.
https://consteril.com/steam-sterilization-cycles-part-2-liquids/
It also says Quote:
It is a best practice to A) validate your liquid loads with hermetically sealed biological indicators
So you are right that the BI needs to be isolated from liquid contact, but you could put it in a hermetic sterilization pouch and run a test if you feel like it.
-------------------- Mold cultivator extraordinaire I also dabble in bacteria I'm also a retard sometimes
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Stipe-n Cap


Registered: 08/04/12
Posts: 7,623
Loc: Canada
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Re: Autoclave Validation and Load Penetration [Re: altford78] 1
#28355268 - 06/11/23 07:12 AM (7 months, 14 days ago) |
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Excellent.
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