Is 7psi enough for for an autoclave?

I, I recently bought a pressure cooker to use as an autoclave for slanting. It cooks at 7psi. Is this enough pressure for autoclaving? Can anyone tell me how long I need to cook for at this pressure to sterilise my gear?

Thx

L

That will not be sufficient to truly "sterilize" items. It will get them very clean however, and cooking things like agar and media for 30 min at 7 psi will likely give you no problems. I would try it out before going and buying something else.

If you do have problems, you can always "Tyndallize" them instead of autoclaving. Tyndallizing is where you heat something up to boiling and then let cool for 3 consecutive days, which gives results similar to autoclaved items. The 1 day between boilings allows the bacterial "endospores" (the part that survives regular boiling) a chance to germinate, and then when you boil next it kills the bacterium. It is more labour intensive, but works great.

Thanks theredben, found a crack on the handle of my new pressure cooker so brought it back an got a larger one that cook at 11.6 psi and received €6 back as it was cheaper. Assume this is good enough for autoclaving?

Thx

L

Larso said:

Thanks theredben, found a crack on the handle of my new pressure cooker so brought it back an got a larger one that cook at 11.6 psi and received €6 back as it was cheaper. Assume this is good enough for autoclaving?

Thx

L

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For proper autoclaving/sterilization, the minimum pressure required (for water, though wort is almost the same) is 15psi. 11.6psi should be better than just boiling, but it shouldn't achieve true sterilization.

Sorry to be the bearer of bad news. If you really want to have a true autoclave capability, I hope you can return the one you have.

emjay said:

For proper autoclaving/sterilization, the minimum pressure required (for water, though wort is almost the same) is 15psi. 11.6psi should be better than just boiling, but it shouldn't achieve true sterilization.

Sorry to be the bearer of bad news. If you really want to have a true autoclave capability, I hope you can return the one you have.

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Thanks Emjay, was just reading the manual with it and it says 'nominal pressure 11.6, maximum pressure 15psi' any idea what exactly that means?? It also says only to put in items that can withstand 130degC?

Go on! Tell me what I want to hear!!!

Thanks

L

If you want to sterilize, you need boiling water or steam at 15 psi for 15 minutes. Boiling water at 15 psi is 250F. I give it 20 minutes to make sure everything is up to temp evenly.

Don't forget to let the steam build and vent for a few minutes before starting your count down as well. Mushroom growing forums are a good place to find info on using pressure cookers for sterilization. I grow shiitakes from time to time and got really great info in books on growing them. Yeast is a fungi and so the culture of yeast is similar in many ways.

Larso said:

Thanks Emjay, was just reading the manual with it and it says 'nominal pressure 11.6, maximum pressure 15psi' any idea what exactly that means?? It also says only to put in items that can withstand 130degC?

Go on! Tell me what I want to hear!!!

Thanks

L

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I suspect that means at 15psi it starts venting a safety valve. Hard to say.

The best answer I can find on the matter is that 11.6psi is what you can expect under normal conditions, which would indicate it's not good enough.

I'd suggest calling the manufacturer if you want to be sure what they mean by nominal pressure. Don't tell them why, though, as CS reps often just tell you want they know you want to hear.

Buy some autoclave tape; it's tape that changes color once it hits sterilization temperatures. Stick it on whatever you want to sterilize, let the pressure cooker rip for an hour, and see what happens.

Thanks guys, going to bring it back and get one that pressures up to 15psi, it'll only cost me another 20euros, and despite what I told my other half I really bought this thing for autoclaving so I might as well do it right. Priced the autocalve tape Ipsiad and I can get it delivered for about 7euros so might as well just spend the 20 and get a pressure cooker that I know will do the job!

L

Bought my new pressure cooker. Made great chicken stock in under an hour . These things are magic. Haven't gotten round to autoclaving yet though. Apparently I can cook pulses and beans in under an hour too without overnight steeping. Great buy!!!

I would consider getting the aforementioned autoclave tape (or other autoclave indicator) anyways. Not just to make sure your pressure cooker can handle 15psi, but even more so to check that your actual PROCESS (ie time x temperature) is sufficient for true sterilization.

emjay - actually the autoclave tape only indicates that temperature was reached, not how long it was held at that temperature. To test time and temperature you need to go with biological indicators ($$$) or a remote probe.

Congrats to the OP for getting a proper pressure cooker.

theredben said:

emjay - actually the autoclave tape only indicates that temperature was reached, not how long it was held at that temperature. To test time and temperature you need to go with biological indicators ($$$) or a remote probe.

Congrats to the OP for getting a proper pressure cooker.

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Ah, my bad. I thought the tape referred to WAS some sort of biological indicator. I guess a simple maximum-temp indicator would be better than nothing, but I'd personally prefer to validate my process *at least once*... especially with a piece of equipment like this that wasn't designed or manufactured with laboratory use in mind.

Hi, I love my pressure cooker. I cook everything with a pressure cooker. What your looking for is a pressure canner with a gauge. All American pressure canners are very good. But back to cooking, try making dinner with that cooker and you'll never go back!!! It cooks 3 to 10 faster. You can make ribs in 15min that are fall of the bone!!!!

How do ye do ribs in it? Even more exciting than yeast ranching

Take your best dry rub and rub the ribs down, then add 1/2-1cup water and the steeming rack so the ribs are out of the water. Then pressure cook at 10psi for 15-17min let cool on it own. It's like you cooked them for hours!! Also hard boiled eggs cook at 10psi for 2min and stop cooking under cold water. The hard boild eggs will peel easer than anyother eggs. My best quick dinner, come home from work, add 5 frozen chicken breast and larg bag frozen vegetables, season to tast, pluse 1cup water (I like to add soy sauce, hot peppers and something acid like vinnagar. Cook for 10min at 10psi = crazy good chicken soup.

O and I have always covered the eggs with water, I don't know what would happen if eggs got pressure steemed.

Thanx Mike , I been doing my ribs at low temp in the oven for 2hrs before finishing on BBQ. That's goin to be much better + are u sure there's only 1 cup water with the chicken? That wudnt make much soup?

Yea, the chicken breast and veggies have lots of water in them that will come out when cooked, that is what makes this so good is the broth. This amount depends on the size of your pressure cooker. I use a 6qt/L to make this. A rule of thumb is add the chicken breast and cover them with water, then add the vegges.