Chicken Stock - Pressing Pause?
New to the boards, thought this would be the perfect place to ask my question. I did a topic search and couldn't find anything for this precise question, but there are many chicken stock threads; I apologize if I missed it!
I started making a chicken stock today and just found out I need to leave my place for a couple of hours. By this time the stock will have been simmering for a little over 5 hours (I simmer for 6 hours, minimum). I'm not comfortable with leaving on my gas stove while I'm out. Does anyone know if I would be able to leave the chicken stock out, unheated, for a couple of hours and then turn it back on to complete simmering, without ruining the stock?
FYI, I very laid back about my stock and don't fuss too much over cloudiness, etc. I don't care if pressing pause will cause any of those types of issues with my stock - I just want to know if it will spoil or generally taste icky this way.
Putting a big hot pot of stock in the fridge is a bad idea, you will end up putting everything in the fridge at risk if you do that.
I'd just put it in the oven on the setting closest to simmer, unless you are worried about keeping an oven on as well.
Other than that I'll say what I always do: Pressure cooker
for a couple of hours. . . I'm assuming 2 hours.
While not scientific at all, and of course I'm not a food safety expert - so take this with those caveats . . . .
I do this all the time and I've never died. You're simmering it for 5 hours (killed most everything) and then you're going to simmer for another hour . . . killing most everything again.
I just cover my stock and pick back up where I left off. No problems and no clouding issues for me either. Next time I'm going to take the temp when I turn the stove off and then again when I turn it back on - because it always still seems very warm (I know - bacteria love warm - I'm just saying it doesn't seem to cool off that much).
Just a quick web search . . . I still say you'll be fine - and it looks like these references support that, especially with simmering for another hour after your "time off" . . .
Sous vide temperature safety zones can be summarized as follow:
Sterilization zone: > 121°C (250°F) for at least 2.4 minutes
Assured Pasteurization zone: > 63°C + (145.4°F)
Start of Pasteurization zone: 60°C (140°F) – 63°C (145.4°F)
Tolerance zone: 55°C (131°C) – 60°C (140°F)
Danger zone: 50°C (122°F) – 55°C (131°F)
Extreme Danger zone: 20°C (68°F) – 50°C (122°F)
According to the Wilderness Medical Society…
Water temperatures at 160° F (70° C) kill all pathogens within 30 minutes.
Water temperatures above 185° F (85° C) kill all pathogens within a few minutes.
So in the time it takes for water to reach the boiling point (212° F or 100° C) all pathogens will be killed, even at high altitude. The moment your drinking water reaches a rolling boil, the water has already become safe to drink.
NOTE: Caveats regarding Safe Water Boil Times:
Boiling water will NOT remove chemical toxins that may be present.
Hi, sunshine: "...you'll re-attain the temperatures necessary to kill whatever could possibly have managed to start to populate the stock..."
I consider this good, practical advice, but it is technically false; I would not try to convince a savvy health inspector of such. The reason it is false is that some spoilage organisms (e.g., Bacillus cereus, Clostridium perfringens, Clostridium botulinum, etc.) generate spores and non-living toxins which the reheating will not kill. Proper reheating will kill the live organisms (and boiling for >10 minutes will destroy most spores), but the toxins remain.
I confess to taking these risks, but the risks are real.
See, this NYT treatment of Chef Michael Ruhlman's risk-taking. http://www.nytimes.com/2011/08/24/din...
Not arguing to the validity of the toxin's presence - as I agree. This "toxins aren't killed" argument comes up a lot in these types of discussions (as they should, and as I mentioned in my earlier post). But keeping it to this topic and scenario. . .
If the stock has been simmered for 4-5 hours - anything in that stock is basically killed. And "technically" the stock will need to cool low enough and long enough to re-enter the "danger zone" - though what is really left in a covered pot to really bloom in the danger zone?
So as a procedural result - any toxin in the stock would have formed from the living organisms present before the first 5 hour simmer - so this "break" in the simmer isn't going to change that. Toxins don't multiply themselves, they are a result of the organism, which we all seem to feel should have been killed during the 5 hour simmer.
So in this instance, any toxin issue that you bring up would be the same risk before and/or after this break . . . no?
Clostridium bacteria are indeed responsible for producing toxins, and also difficult to kill. But their enterotoxin itself can be denatured by boiling; the endospores (a dormant cell of the bacterium with a kind of shell that makes it hard to kill) are able to survive boiling temperatures. You've got it backwards. B. Cereus is also an endospore former that will not reliably be killed by boiling. It releases three different toxins, which might be more heat-tolerant than clostridium toxins.
Also of note, staph aureus (which is comparatively easy to kill) can release an enterotoxin that is stable at boiling temperature.
Most of this is academic though for one reason - taking something off the heat for just two or three hours before reboiling is simply not enough time for either the release of toxins or the multiplication of bacteria to dangerous levels. If the OP were debating whether to leave the kitchen for 6 or 8 or 12+ hours, heat stable toxins released by b. cereus or staph aureus would be a concern. But anything under 4 hours meets even the most stringent of kitchen safety standards.
Even using the very conservative food safety standards recommended by the USDA, you would have up to 4 hours for food to pass from 140 degrees to below 40 degrees before there is any considerable danger. If you have a big pot of stock at a simmer, it would take a little while to drop below 140 in the first place... and then you would have several hours to reheat it above 140 with very little risk.
If you're stepping out for 'a couple hours,' cover the pot, reheat it upon returning home, and don't worry about it in the least.
Just take it off heat and reboil when you get home. Bugs wouldn't have had a chance to grow anyway (it's a sterile environment), and whatever did grow would die off in the second boil.