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I was making turkey broth last night in the oven (turkey bones and leftover meat in a stockpot in a 170 F oven for 6+ hours). I read about this technique on a chef's blog, which I can find if needed.

Then I got to thinking. The broth certainly has bacteria in it from the turkey carcass. And all those bacteria are sitting in water, with plenty of proteins floating around in a nice toasty oven. Is all this bacteria + protein + water + heat safe? It seems like broth should be unsafe at the least. Is 170F enough to kill the bacteria that would be present here?

On the other hand, chefs have been doing this for quite a while and everyone seems fine.

jcollum
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2 Answers2

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170 degrees is perfectly fine.

To talk bacteria, you have to take into account two factors: temperature, and time. Anything between 40 and 140 is good for them, anything above 140 is bad. At the same time, food in the dangerzone that is eaten/cooked/frozen promptly, is fine, because it takes time to build up a colony of harmful proportions.

In this case your temperature is 170 degrees, which is hot enough to kill most common bacteria instantly (Milk is pasteurized in the 160s), and then you keep it at that temperature for hours? The toughest common bacteria (C. botulinum) dies very quickly at 180 degrees...It's the only one I know off the top of my head that doesn't immediately die in the 170 range. And keeping your stock at 170 for 10 minutes or so will kill any C. botulinum that may have somehow found it's way inside it.

You've got nothing to worry about.

(Basics of TDT calculation)

Satanicpuppy
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The broth is safe for consumption as long as the liquid has reached an internal temperature high enough to kill bacteria that might be present - I'd go with the guidelines of the internal temperature you'd use for a turkey.

At the same time, broths in general are usually considered to have a short shelf life of around three days in the refrigerator because broth is a good breeding ground for bacteria. If you plan to keep this broth around, do so in the freezer or make it shelf-stable and use a pressure canner.

justkt
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  • But there's sooo much more bacteria kicking around on the inside of the turkey (not in the meat) -- and that part goes in your broth directly. No one's rubbing the turkey meat around the inside of the carcass before they eat it. You have a good point, I'm just playing devil's advocate. – jcollum Nov 30 '10 at 20:28
  • The inside of the turkey is exposed to the same heat that the outside gets, so why would there be more bacteria there than in the meat? – Mrs. Garden Nov 30 '10 at 20:32
  • Most milk is pasteurized at 165 degrees, by the way. A broth kept at 170 degrees overnight should be fine, in my opinion. – Mrs. Garden Nov 30 '10 at 20:35
  • @jcollum - if your turkey hasn't been cooked through to the appropriate temperature, you have problems long before it gets to broth. – justkt Nov 30 '10 at 21:13
  • @MrsGarden, @justkt: Hard to say if that's actually true. The inside of the turkey is often stuffed with veggies or spices or stuffing. I've never actually measured the temp of the inside stuff (I don't like to put the stuffing in the turkey). – jcollum Nov 30 '10 at 21:25
  • @MrsGarden re: milk: different bacteria here... the inside of the turkey would likely be exposed to E. Coli from the innards during the butchering process. To be fair, I have no idea if E. Coli live inside of turkey gullets (or whatnot). – jcollum Nov 30 '10 at 21:27
  • @jcollum: You're right, the interior of the turkey cooks slower, which is why the food safety agencies recommend cooking whole birds to a temperature of 185° F or 85° C, to be on the safe side. It only takes 30 minutes to kill salmonella at 140° F; anything over 170° F or so is basically instant death; and we're talking about at least 180° for several hours. E. Coli generally doesn't live in turkey, you're thinking of beef. – Aaronut Nov 30 '10 at 22:31
  • @Aaronaut: alright, you've convinced me, thanks for the thoroughness – jcollum Nov 30 '10 at 22:32
  • @mfg: I would have asked a separate question about that, but FYI, no, it does not. Bacteria leave toxins behind when they reproduce, and re-boiling will kill the bacteria but won't get rid of the toxins. Imagine if instead of the fridge for a week, you'd left it out on the counter for a month; think there's *any* hope of saving that broth? – Aaronut Dec 01 '10 at 19:15