sterilizing agar plates after use.

I inherited an electric pressure cooker with the job and was instructed to use it to sterilize all agar plates after use and before disposing of them. I was just looking online at something totally different when I came across a statement discouraging the use of electric pressure cookers instead of an autoclave, because they don't hold constant pressure.

So my question is this 'What do people do to sterilize plates after use so they can be safely put in a general waste bin?'
 
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An autoclave is a fancy name for a pressure cooker (electric or remote heating) - look at the specs for your one - it will tell you the temperature and pressure with any tolerances
CLEAPSS recommend that 121°C for 15 minutes of steam is essential for sterilising water-based materials
15psi/103kPa/1.04bar ensures steam at a temperature of 121°C.
 
I inherited an electric pressure cooker with the job and was instructed to use it to sterilize all agar plates after use and before disposing of them. I was just looking online at something totally different when I came across a statement discouraging the use of electric pressure cookers instead of an autoclave, because they don't hold constant pressure.

So my question is this 'What do people do to sterilize plates after use so they can be safely put in a general waste bin?'
I would also check the pressure will be high enough.
 
I inherited an electric pressure cooker with the job and was instructed to use it to sterilize all agar plates after use and before disposing of them. I was just looking online at something totally different when I came across a statement discouraging the use of electric pressure cookers instead of an autoclave, because they don't hold constant pressure.

So my question is this 'What do people do to sterilize plates after use so they can be safely put in a general waste bin?'
If you can't find the spec for your autoclave then buy some 'autoclave tape' you put this in the pressure cooker with your samples - it has an indicator to show that you have sterilized properly most school suppliers stock such tape - for example https://www.science2education.co.uk/product/SLS1610
Please note it is the temperature and time that is significant, the pressure is only a means to get temperature up to 121 degrees.
Autoclavable tape indicates when steam sterilisation has occurred by means of a visible black strip which shows after autoclaving (3mins @ 134°C, 15 mins @ 121°C)
 
If you can't find the spec for your autoclave then buy some 'autoclave tape' you put this in the pressure cooker with your samples - it has an indicator to show that you have sterilized properly most school suppliers stock such tape - for example https://www.science2education.co.uk/product/SLS1610
Please note it is the temperature and time that is significant, the pressure is only a means to get temperature up to 121 degrees.
Autoclavable tape indicates when steam sterilisation has occurred by means of a visible black strip which shows after autoclaving (3mins @ 134°C, 15 mins @ 121°C)
autoclave tape is not an indication of sterility, you need a browne tube or TST sterilisation strips

 
autoclave tape is not an indication of sterility, you need a browne tube or TST sterilisation strips

does the same thing but a lot cheaper
 
does the same thing but a lot cheaper
No it does not.

It is important to note that the presence of autoclave tape that has changed color on an item does not ensure that the product is sterile, as the tape will change color upon exposure only. For steam sterilization to occur, the entire item must completely reach and maintain 121°C for 15–20 minutes with proper steam exposure to ensure sterilization.
 
Read the specs for your post on TST strips - yes the same
Tape will change in an oven it does not check time temp and pressure as any other microbiologist will tell you.

cleapss say

Autoclave tape is a useful way of showing which containers have been heated in a pressure vessel. However, it does NOT indicate that full sterilisation has taken place as it does not take into account pressure and time

http://science.cleapss.org.uk/Resource/GL272-Sterilising-for-microbiology.pdf
 
Tape will change in an oven it does not check time temp and pressure as any other microbiologist will tell you.
Fair point @Paul, I'm looking at a different CLEAPSS guide which doesn't mention pressure for strips GL126 says 'Test the unit before use. Sterilisation testing strips or vials show a colour change on exposure to the specified sterilisation temperature and time'. This is mirrored by the specs for the TST strips. I can't see the difference between the strips and the tapes although I've found your document GL272 which as you say mentions pressure. The bottom line is the part of the tape exposed shows it has been at 121 degrees for 15 mins so just make sure its in the middle of your samples. Big difference between £40 and £3 so I guess yours are more accurate?
 
Fair point @Paul, I'm looking at a different CLEAPSS guide which doesn't mention pressure for strips GL126 says 'Test the unit before use. Sterilisation testing strips or vials show a colour change on exposure to the specified sterilisation temperature and time'. This is mirrored by the specs for the TST strips. I can't see the difference between the strips and the tapes although I've found your document GL272 which as you say mentions pressure. The bottom line is the part of the tape exposed shows it has been at 121 degrees for 15 mins so just make sure its in the middle of your samples. Big difference between £40 and £3 so I guess yours are more accurate?
autoclave tape is just lead carbonate based, which decomposes to lead(II) oxide.
 
autoclave tape is just lead carbonate based, which decomposes to lead(II) oxide.
Interesting - so how can the suppliers of the tape get away with saying ....'Autoclavable tape indicates when steam sterilisation has occurred by means of a visible black strip which shows after autoclaving (3mins @ 134°C, 15 mins @ 121°C) '
Also Lead oxide or carbonate isn't black so it can't be the only thing on the tape.
 
Interesting - so how can the suppliers of the tape get away with saying ....'Autoclavable tape indicates when steam sterilisation has occurred by means of a visible black strip which shows after autoclaving (3mins @ 134°C, 15 mins @ 121°C) '
Also Lead oxide or carbonate isn't black so it can't be the only thing on the tape.
some ink as well i think.
 
some ink as well i think.
probably:)
No doubt the the strips are going to be the way to go to be certain but I find it worrying that suppliers can make statements about a product which may not do what they say.

Just looking at the Browne TST strips to get to the bottom this and they say...
'The term TST is an abreviation of Time/Steam/Temperature, the critical parameters for a sterilisation cycle. Class 6 indicators provide a level of validation of all three parameters, unlike other classes of strip which may only provide the results for the presence of steam in the chamber. '

Fisher scientific say this about Browne TST strips in their specs 'When placed inside trays, packs or pouches, a TST Control Emulating Indicator will confirm that good quality steam has penetrated to the point of placement'

No mention of pressure by either, so C:LEAPSS are in error here with the GL272 statement.
 
I think they might mean steam sterilisation maybe.

Steam Sterilization
Process
Steam sterilization is achieved by exposing the items to be sterilized with saturated steam under pressure. Steam enhances the ability of heat to kill microorganisms by reducing the time and temperature required to denature or coagulate proteins in the microorganism
some interesting info on Mr Browne
 
We do use TST strips when we dispose of our agar plates. I do remember being told that autoclave tape is not sufficient to certify that the load is sterile.
 
We do use TST strips when we dispose of our agar plates. I do remember being told that autoclave tape is not sufficient to certify that the load is sterile.
I suppose you've read the discussion with Paul - suppliers saying the tape is proof of 121 degrees and 15mins whereas CLEAPSS says it isn't. Bit like suppliers selling portable bunsens which CLEAPSS say are unsafe.
 
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