Is my chicken stock safe to eat?

January 21, 2019 7:18 PM

I made chicken stock in my instant pot and forgot about it until the next morning. Do we think it’s safe to eat?

- ingredients were a chicken carcass and some veggie trimmings
- ingredients came from the freezer
- chicken carcass was put in the freezer within 2hrs of the bird originally coming out of the oven
- stock was cooked on high pressure in instant pot
- instant pot was turned fully off after several hours of cooking (so it was not on Keep Warm overnight)
- lid was on instant pot overnight
- when I opened it in the morning, liquid was lukewarm and smelled delicious

posted by sixswitch to Food & Drink (17 answers total)

My husbands family regularly eats soup left on the counter overnight. They reboil it first. I typically don’t eat it but they haven’t died so
posted by St. Peepsburg at 7:26 PM on January 21, 2019 [1 favorite]

Yeah, absofuckinglutely reboil it if you do decide you're going to eat it.
posted by nebulawindphone at 7:33 PM on January 21, 2019 [1 favorite]

Best answer: Well what you've essentially done there is made a bacterial growth medium—and then autoclaved it. We used to do that all the time when I worked in a microbiology lab, and as long as nobody took the tinfoil off, the beakers of sterilized media would remain sterile for months at a time, just sitting on a shelf in a room where bacteria that specifically loved that type of medium (E. coli, mostly) were being intentionally bred and cultured.

Bacteria are invisible, but not magical. They don't spontaneously generate—if they're not present somewhere, they need to be introduced somehow. A sealed, sterilized container does not allow that to happen.

So I'd say you're probably pretty fine there.
posted by Anticipation Of A New Lover's Arrival, The at 7:33 PM on January 21, 2019 [24 favorites]

How long was the stock cooked? Was it on a soup cycle (30 minutes high pressure)? If so, and if the lid were never taken off after cooking, I think it's fine (assuming you put it straight into the fridge once you opened it.) I think it's pretty sterile in there after a soup cycle, as long as the lid is undisturbed.
posted by fingersandtoes at 7:35 PM on January 21, 2019

Response by poster: AoaNLA: that was kind of my thinking, thanks for articulating it in science-y terms
posted by sixswitch at 7:36 PM on January 21, 2019 [1 favorite]

And hey, one thing that's come up again and again in several threads on the Blue and Green just in the last couple of days is that if your food has become toxic due to bacteria, re-heating it doesn't help. The toxins produced by the bacteria will remain even after the bacteria have been killed, and they are what make you sick. Although if it hasn't actually gone bad, re-boiling would render it sterile again and put a stop to any incipient bacterial growth that may have been underway. An airtight container that was heated and held well above the boiling point of water and then never opened will not have bacteria in it, however.
posted by Anticipation Of A New Lover's Arrival, The at 7:37 PM on January 21, 2019 [8 favorites]

Response by poster: It was on for about 3hrs at high, which seems like the Instant Pot equivalent for my stock routine “simmer on the stove all day long”.
posted by sixswitch at 7:38 PM on January 21, 2019

I wouldn't - but I am extremely paranoid about chicken.
posted by schwinggg! at 7:39 PM on January 21, 2019

Response by poster: AoaNLA: one follow up question! A boiling liquid never actually gets above 100deg, right? But the Instant Pot is a sealed system so presumably my stock was heated to “well above” 100deg?

And yeah, I thought through the “time on the counter” for exactly that reason (leftover toxins).
posted by sixswitch at 7:40 PM on January 21, 2019

You might find this lengthy article on exactly your question of use and interest. Some select quotes, starting with the scary part:

Boiling does kill any bacteria active at the time, including E. coli and salmonella. But a number of survivalist species of bacteria are able to form inactive seedlike spores. These dormant spores are commonly found in farmland soils, in dust, on animals and field-grown vegetables and grains. And the spores can survive boiling temperatures.

After a food is cooked and its temperature drops below 130 degrees, these spores germinate and begin to grow, multiply and produce toxins. One such spore-forming bacterium is Clostridium botulinum, which can grow in the oxygen-poor depths of a stockpot, and whose neurotoxin causes botulism.

Once they’ve germinated, bacteria multiply quickly in nourishing stock. They can double their numbers every 90 minutes at room temperature, every 15 minutes at body temperature. A single germinated spore can become 1,000 bacteria in a matter of hours, a billion in a few days.

... and ending with the remediation:

Any active bacteria are killed by holding the stock for a minute at 150 degrees or above, and botulism toxin is inactivated by 10 minutes at the boil.

posted by mph at 7:42 PM on January 21, 2019 [3 favorites]

Best answer: Boiling water gets to exactly 100°C at STP, by definition. Stock has stuff in it so it'll be a bit higher but yeah, the whole point of the Instant Pot (and autoclaves) is that it allows you to take water past the 100°C mark without boiling it, by containing it under pressure. That is its magic.
posted by Anticipation Of A New Lover's Arrival, The at 7:43 PM on January 21, 2019 [1 favorite]

Best answer: Three hours at 240°F (what Instant Pots get to on High) is enough to destroy botulinum spores. The "150 degrees" referenced in mph's link is degrees Fahrenheit.
posted by Anticipation Of A New Lover's Arrival, The at 7:52 PM on January 21, 2019 [2 favorites]

Although the high pressure boil does basically what an autoclave does, killing ALL bacteria, the pressure-relief after cooking brings in non-sterile air. The chances of that air introducing something deadly are low, but it's not quite the same as AoaNLA's first reply, which posits an airtight container. The de-pressuring Instant Pot is not airtight.

But I'd eat it after boiling some more.
posted by anadem at 8:00 PM on January 21, 2019 [4 favorites]

Response by poster: Thanks all!
posted by sixswitch at 8:10 PM on January 21, 2019

Are you sure the pressure-relief brings in outside air? Seems to me that it should simply release the pressurized air (air flowing "out" only, still sterile inside) until it equalizes with the surrounding atmosphere at which point the float valve closes and it becomes sealed again. I'm not even sure how outside air would get in when there's positive pressure inside the vessel.
posted by Anticipation Of A New Lover's Arrival, The at 3:19 AM on January 22, 2019 [6 favorites]

I would have some concern, so I would re-boil the stock for 30 minutes. In addition, I would test it by eating half a cup or so and waiting a day to see if there are repercussions.

Most food poisoning is caused by live germs. Staph and other germs produced toxin that survives boiling, so caution is advisable.

That said, cooked well and left in the closed container is likely ok.
posted by theora55 at 6:53 AM on January 22, 2019

I'm not even sure how outside air would get in when there's positive pressure inside the vessel.

Well, in that scenario, of course not, but the IP won't stay pressurised that entire time. It slowly returns to atmospheric (based on my usage of one) over a few hours. I think it will have been at atmosphere and cooling long before the morning so could theoretically have drawn in air as the contents cooled and contracted. The IP doesn't seal immediately and vents out as it heats up, so if you completely sealed it from the point of pressure, you would have a negative pressure in the IP when it got back to room temp. But it doesn't seal perfectly once pressure is off so a very small volume of air would have been pulled in as the contents dropped from 'the temp at which the seal valve clicked in' to 'lowest temp overnight'.

I would suspect that this is a tiny amount of air and likely inconsequential in terms of bacteria, but it would pull in outside air.
posted by Brockles at 7:39 AM on January 22, 2019