Pressure cooker - poor sanitation

[Piotr]

Looks like my pressure cooker doesn't sanitize at all.

Here is the story:
I wanted to prepare some wort for a starter. I sterilized it together with a jar in a pressure cooker, and I put it aside, covered loosely with a lid; in room temperature. Theoreticaly it should be sterile and stay sterile forever, but after two days it shows signs of spontaneus fermentation (thin foam on the surface).
Either my pressure cooker doesn't boil the wort inside the jar, or the bugs actually CAN crawl under the lid, or I have some temperature-resistant bugs.

I sanitized like this: I pour 2 liters of wort into a big 2.5 liter jar; I put it in the pressure cooker (the lid of the jar too), with ~2 liters of water - it covers about 3/4 of height of the jar; I close the cooker, and I let it boil 20 min (counting from the moment when I see the steam escaping). After it cools down a bit I open the cooker, I place the lid on the jar, and only then I take it out of the jar.

 

[SpanishCastleAle]

Are you sure 20 min. is enough to heat the wort inside the jar to boiling? Seems like it would take a while for the wort in the jar to boil but that's just a seat-o-the-pants guess. When we boil wort the pot is sitting on a red hot burner or flame...way hotter than inside a pressure-cooker.

 

[BioBeing]

I used to use a pressure cooker to sterilize media for growth of microrganisms in the lab. It can work, and 20 min should be long enough. You just need enough water outside to prevent it boiling dry. The only things I can think that might be wrong are the lid was not on the jar [put it on loosely before you cook it (do not screw it on all the way, or you will have an explosion!)]; and 2 liters of wort might have been too much - maybe it did not come all the way to a boil?

 

[Scut_Monkey]

Perhaps the wort was not boiling but I doubt this as it seems like you were making a small starter. What was the volume of the starter? Also, make sure you let the pressure cooker reduce its pressure on it's own without venting it to help reach sterility.

Lastly, and I feel most importantly, pressure cookers are crap these days. It's very hard to find one that actually goes to 15psi which I believe is necessary. Everybody and their mother sells pressure cookers but the vast majority only go to 10psi. This lets them make them for cheap but still allows you to cook pressure cooker fast. However, sterilization I feel is compromised. Check your pressure cooker.

 

[JoeMama]

Every time I have used a PC for sterilization purposes it has always been for AT LEAST an hour from the time the rocker starts rattling. Granted growing fungus demands a higher level of sterility, but I never failed using this rationale.
-Me

 

[Catt22]

Are you sure 20 min. is enough to heat the wort inside the jar to boiling? Seems like it would take a while for the wort in the jar to boil but that's just a seat-o-the-pants guess. When we boil wort the pot is sitting on a red hot burner or flame...way hotter than inside a pressure-cooker.

The burner may be red hot, but the wort will never reach anything close to that temperature or the temperature inside of a pressure cooker. The boiled wort will only reach approximately 212 F unless the containment vessel is pressurized. IIRC, the temp inside a pressure cooker at the typical 15 psi reaches something like 257 F.

 

[Piotr]

Thank you for all your suggestions.

Yes, I have cheap 10 psi cooker - what temperature can it reach at 10 psi?
Yes, I kept the lid separate in the cooker.
Yes, it is possible that only the water outside reached the boiling, not the wort inside the jar (almost 1/2 gallon)

I guess all my beers from last year are more or less infected

 

[Catt22]

Looks like my pressure cooker doesn't sanitize at all.

Here is the story:
I wanted to prepare some wort for a starter. I sterilized it together with a jar in a pressure cooker, and I put it aside, covered loosely with a lid; in room temperature. Theoreticaly it should be sterile and stay sterile forever, but after two days it shows signs of spontaneus fermentation (thin foam on the surface).

I think I see what may be the problem. When you removed the jar from the pressure cooker and set it aside, it was only covered loosely with the lid. When the wort and air/steam inside the jar cools, it contract and will inevitably draw in air. The air could well contain contaminants such as bacteria or mold. The standard mason jars used for canning have a lid with a gasket and a sealing ring to hold the lid in place to insure a proper seal. IIRC, the procedure is to place the jars in a pressure cooker with the lids on them held in place by the ring piece. The ring is not tightened at this point which allows steam and expanding air to escape. After removing the jars from the cooker, the rings can be tightened down to initiate a good seal. As the contents cool and contract, a partial vacuum is formed inside the jar preventing air and contaminants from entering and I think you can safely remove the rings when the jars are cool without disrupting the seal. You may be better off using multiple quart size mason jars designed for canning. I'm not an experienced pressure cooker user, so don't follow my advice solely. I'd suggest reading the cooker manual to determine the correct procedure.

 

[WortMonger]

10 psi should get you to around 212F (so you just need to cook longer to achieve a good sterile wort). Make sure you have the lids on and the screw rings tight enough the lids won't come off in the cooker. Check that you have not over-filled your jars with wort (I think about an inch of head space is sufficient in Kerr and Mason jars. Allow the PC to cool on its own. Then open the lid on the PC and tighten the lids. Take the jars out with a towel for heat protection for your hands, and turn them upside-down on a towel. Then let them cool down to room temperature. There has to be a vacuum present in the jars for it to remain sterile for storage. After jars are cool, check the lids for them to be sunken in proving you have accomplished a vacuum during your "canning" of your wort.

 

[SpanishCastleAle]

The burner may be red hot, but the wort will never reach anything close to that temperature or the temperature inside of a pressure cooker. The boiled wort will only reach approximately 212 F unless the containment vessel is pressurized. IIRC, the temp inside a pressure cooker at the typical 15 psi reaches something like 257 F.

I must not have worded it very well Catt22...the fact that it only gets to ~257 F inside the PC is why I thought it would take longer. Because you're not heating it with a red hot burner...but rather a 257 F PC.

10 psi should get you to around 212F (so you just need to cook longer to achieve a good sterile wort).

Is this a typo Wortmonger? Water at atmospheric P boils @ 212 F...with 10 psi above atmospheric it should boil hotter no?

 

[Catt22]

10 psi should get you to around 212F

Boiling is approximately 212 F with exceptions for high altitudes. 10 psi will put it somewhere near 248 F & 15 psi will push it to 257 F or so.

Most pressure canners I have seen are designed to cook at 15 psi, although some are also adjustable using different weights for the rocker thingy. I'm pretty sure that all of the pressure cookers designated as "canning" types are at least 15 psi as this is the standard set by the US Department of Agriculature way back in 1917.

 

[BioBeing]

You probably do need 15 psi for absolute sterility. Didn't know they made 10- psi ones - it was a long time ago I did it! But our lab autoclaves (exact same principle, just bigger scale) are 15 psi.

 

[Brewers Hardware]

I think I see what may be the problem. When you removed the jar from the pressure cooker and set it aside, it was only covered loosely with the lid. When the wort and air/steam inside the jar cools, it contract and will inevitably draw in air. The air could well contain contaminants such as bacteria or mold. The standard mason jars used for canning have a lid with a gasket and a sealing ring to hold the lid in place to insure a proper seal. IIRC, the procedure is to place the jars in a pressure cooker with the lids on them held in place by the ring piece. The ring is not tightened at this point which allows steam and expanding air to escape. After removing the jars from the cooker, the rings can be tightened down to initiate a good seal. As the contents cool and contract, a partial vacuum is formed inside the jar preventing air and contaminants from entering and I think you can safely remove the rings when the jars are cool without disrupting the seal. You may be better off using multiple quart size mason jars designed for canning. I'm not an experienced pressure cooker user, so don't follow my advice solely. I'd suggest reading the cooker manual to determine the correct procedure.

This is the procedure I use. The lids need to be on the jars and as they start to cool they will pull a vacuum. I've used wort canned 2 years ago with no issues. It's clear as can be and smells as good as day one.

 

[Brewers Hardware]

I'll also comment that you should never, ever, try to speed up the cooling process! I tried to cool mine quicker and release the pressure before it was ready.....

Turns out that'll make the wort boil in the jars and creates one HELL of a mess!

 

[HSM]

Looks like my pressure cooker doesn't sanitize at all.

Here is the story:
I wanted to prepare some wort for a starter. I sterilized it together with a jar in a pressure cooker, and I put it aside, covered loosely with a lid; in room temperature. Theoreticaly it should be sterile and stay sterile forever, but after two days it shows signs of spontaneus fermentation (thin foam on the surface).
Either my pressure cooker doesn't boil the wort inside the jar, or the bugs actually CAN crawl under the lid, or I have some temperature-resistant bugs.

I sanitized like this: I pour 2 liters of wort into a big 2.5 liter jar; I put it in the pressure cooker (the lid of the jar too), with ~2 liters of water - it covers about 3/4 of height of the jar; I close the cooker, and I let it boil 20 min (counting from the moment when I see the steam escaping). After it cools down a bit I open the cooker, I place the lid on the jar, and only then I take it out of the jar.

Your pressure cooker works fine. If you want to sterlize anything in a PC it's 90 minutes at 15 psi.

 

[WortMonger]

OOOPS!!!! My bad, and sorry it took me so long to come back to my mistake. Temperature in the canner/cooker at 10 psi is close to 250F. I had a brain fart and just typed 212F because my brain was thinking boiling. Funny enough, there is no boiling going on except at first, lol. I got all my info from this cool canning site, great recipes too.

 

[JKoravos]

I think I see what may be the problem. When you removed the jar from the pressure cooker and set it aside, it was only covered loosely with the lid. When the wort and air/steam inside the jar cools, it contract and will inevitably draw in air.

^^^ This.


If it isn't sealed when you remove it from the canner, you risk contamination. Air WILL be sucked in, there's no avoiding it. If you just cover it loosely you are gambling on whether or not the air that gets in has contaminants in it or not.

This time you gambled and lost.

 

[Synovia]

^^^ This.


If it isn't sealed when you remove it from the canner, you risk contamination. Air WILL be sucked in, there's no avoiding it. If you just cover it loosely you are gambling on whether or not the air that gets in has contaminants in it or not.

This time you gambled and lost.

Right, but don't most people, when making starters, etc, boil in pyrex and just cover with foil? Why aren't they all getting infections?

 

[WortMonger]

Right, but don't most people, when making starters, etc, boil in pyrex and just cover with foil? Why aren't they all getting infections?

Because the yeast starts much more quickly and finishes before the bad bugs can take hold. This is stored food that is un-preserved. They will thrive if they get in.

 

[Gremlyn]

From a scientific standpoint, 25 minutes at temperature if enough to consider the wort sterile. When I used to make agar in an autoclave, it was 25 mins at 15 psi IIRC. We had a setting to bring the temp up slowly for liquids to make sure they got to temp appropriately. Once the PC is up to temp, the wort won't be far behind. I don't think time is your issue here at all. Definitely try with the lid on and the ring put on loosely over it next time.

 

[JKoravos]

Because the yeast starts much more quickly and finishes before the bad bugs can take hold. This is stored food that is un-preserved. They will thrive if they get in.

Right, for 99.9% of starters, people are pitching the yeast as soon as the wort is cool so the yeast completely out competes any bacteria which makes it's way into the wort (and it does make it's way into the wort).

From a scientific standpoint, 25 minutes at temperature if enough to consider the wort sterile. When I used to make agar in an autoclave, it was 25 mins at 15 psi IIRC. We had a setting to bring the temp up slowly for liquids to make sure they got to temp appropriately. Once the PC is up to temp, the wort won't be far behind. I don't think time is your issue here at all. Definitely try with the lid on and the ring put on loosely over it next time.

Yeah, IMO, the wort doesn't lag behind the PC barely at all unless you have your PC on a jet burner. It takes my PC a pretty damn long time to get up to 15psi. I would be shocked if the wort lags more than a degree or two behind the water in the PC.


Generally, it's a bad idea to leave unsealed wort out like the OP, but if you absolutely had to, you could put a few paper towels (the more the better) over the top of the container and secure them tightly with some elastic bands. If you're lucky the paper towels are "sterile" enough and provide enough filtration to keep the great majority of the bacteria out (maybe even soak the first paper towel layer in Star-San or alcohol). Granted, this is conjecture on my part, but I think it might work. You need to let the pressure equalize without unfiltered air getting into the head space.

 

[Gremlyn]

Generally, it's a bad idea to leave unsealed wort out like the OP, but if you absolutely had to, you could put a few paper towels (the more the better) over the top of the container and secure them tightly with some elastic bands. If you're lucky the paper towels are "sterile" enough and provide enough filtration to keep the great majority of the bacteria out (maybe even soak the first paper towel layer in Star-San or alcohol). Granted, this is conjecture on my part, but I think it might work. You need to let the pressure equalize without unfiltered air getting into the head space.

I would actually recommend covering the jar with aluminium foil while it is in the PC. This will prevent it from blowing up the jar for sure, and you can leave the foil covering the jar until it is time to use it.

 

[JKoravos]

I would actually recommend covering the jar with aluminium foil while it is in the PC. This will prevent it from blowing up the jar for sure, and you can leave the foil covering the jar until it is time to use it.

That's pretty much the same as what the OP did. If you cover it in aluminum foil air will still get sucked in as it cools. Now, if you were to leave it in the pressure cooker until the entire thing came back to room temp, then that would probably be OK.

Actually, now that I think about it, the best way is to leave it in the pressure cooker until you need to use the starter.

 

[JKoravos]

I sanitized like this: I pour 2 liters of wort into a big 2.5 liter jar; I put it in the pressure cooker (the lid of the jar too), with ~2 liters of water - it covers about 3/4 of height of the jar; I close the cooker, and I let it boil 20 min (counting from the moment when I see the steam escaping). After it cools down a bit I open the cooker, I place the lid on the jar, and only then I take it out of the jar.

From this quote it it doesn't look like you were sterilizing at 250, but only boiling it, correct?

 

[Piotr]

From this quote it it doesn't look like you were sterilizing at 250, but only boiling it, correct?

No, it means I start counting the boiling time as soon as I see steam escaping from safety valve on the PC, that means it reached the desired pressure (10 psi in my case)

 

[JKoravos]

ok, I see. I was a little confused by the wording.

 

[Gremlyn]

That's pretty much the same as what the OP did. If you cover it in aluminum foil air will still get sucked in as it cools. Now, if you were to leave it in the pressure cooker until the entire thing came back to room temp, then that would probably be OK.

I made media in the lab that way for years and never had a problem with sterility. But you're right, it wouldn't to leave the PC sealed until it's time to use the wort, though you then wouldn't know if anything went wrong inside until it was too late.

 

[JKoravos]

I made media in the lab that way for years and never had a problem with sterility. But you're right, it wouldn't to leave the PC sealed until it's time to use the wort, though you then wouldn't know if anything went wrong inside until it was too late.

Which is why people either can it, or pitch the yeast right away.