DIY Autoclave from A Pressure Cooker

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DIY Autoclave from A Pressure Cooker

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A pressure canner allows you to create very hot temperatures by adding heat to steam under pressure, this allows pressure canners to be used for all sorts of things.

In this post we will use it to sterilize equipment. An autoclave is used in hospitals and doctor’s offices to sterilize equipment, and while I am not advocating using this to sterilize equipment for home surgery – being able to sterilize things (for brewing as an example) is very useful

First, because you are using a pressure vessel you need to read your manual. I am by no means a safety nazi, I don’t want you to blow your face off when you failed to follow basic safety guidelines.

Next realize that pressure cookers are not designed to reach the temperatures necessary for complete sterilization.   While I think it is a good process for ensuring you don’t contaminate your fermenting or brewing recipes with bad yeast, I would not trust it for medical equipment unless it was the last resort and I would die anyway…

You have to keep whatever you are sterilizing off the bottom of the cooker, so make a wire mesh bottom for the pressure cooker autoclave (a steamer basket also works).

A pressure cooker uses steam, which is formed when water reaches its boiling point. The steam is what is doing the sterilization, and therefore anything sitting in the water at the bottom of the pressure pot is not being sterilized.

Autoclaving is typically used to sterilize laboratory glassware, metal equipment and instruments, and to kill organisms in biological waste. It does this by filling the container with steam at a high pressure. The amount of time the contents are exposed to this high pressure steam is critical. At 15 PSI, a pressure cooker produces steam at 121 degrees Celsius. At this temperature and pressure, thermal death time for most bacteria is about 15 minutes, although some microorganisms will be capable of surviving this treatment .

Only use laboratory-grade Pyrex (borosilicate glass) and stainless-steel materials only. You can also wrap utensils or the open tops of glassware in aluminum foil.

Mason jars (Ball) can also be used in much the same way as Pyrex. (NEVER screw down the lid of any jar inside of an autoclave or pressure cooker. If you autoclave regular glass you also run the risk of having said glass explode).

Place two cups of water in the bottom of the pot, then the support stand, followed by a whatever you are needing to sterilize (FYI you cannot sterilize something that is not clean). Put the lid on and pressure cooked according to the manufacturer’s instructions for 15.

Do not leave the pressure cooker unattended. A watched pressure cooker will in fact boil, and hopefully not explode since you take care of your pressure cooker lid, seal, and emergency release valve according to manufacturer’s instructions.

After the 15 minute sterilization time is up you should allow the pressure cooker to release the pressure by the slowest method possible. Let the pressure cooker sit for an hour and a half (closed to maintain a sterile environment inside) to let it come back to room temperature as slowly as I could so as to not have a problem with the glass mason jar.

Since we are talking about sterilization I wanted to give you a source for further study:

Sterilization of Surgical Instruments Using A Pressure Cooker

Wilfredo L. Mirasol, Jr., M.D.., Rizalino F. Felarca, M.D., and Napoleon B. Alcedo, M.D., Department of Ophthalmology, UERMMMC, Aurora Blvd., Quezon City

Purpose: To explore the utility of the pressure cooker as an alternative method for sterilization.

Methods: Sterile ophthalmic instruments were inoculated with known organisms and sterilized using either a Pelton and Clane Autoclave, immersion in gluteraldehyde, a gas-clave or a pressure cooker at 15PSI for 30 minutes. Samples were then cultured after the sterilization process.

Results: There was no growth of organisms in any of the groups.

Conclusion: Sterilization of ophthalmic instruments using a pressure cooker can kill common microorganisms as efficiently as the conventional methods.

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