11

If I slow-cook a turkey over low, low heat for 12-18 hours, how does it stay "safe" when the turkey has been in the danger zone for a large majority of the cooking time?

I've been slow-cooking turkeys on my Big Green Egg for years. I use lump coal and wood chips (for smoke) and manage to keep the cooking temperatures between 200°F-250°F (93-121 °C) for the entire time (12-18 hours). The turkey is unstuffed and placed on a rack over a roasting pan. It is cooked until the internal temperature has reached 165°F (white meat) and 175°F (dark meat).

Certainly the finished cooking temperatures has killed any food-borne bacteria, but what makes this method safe when the turkey spends many, many hours in that "danger zone" building up toxins until it is done?

  • You're saying you're keeping your cooking temperature between 200 and 250F for the entire cooking time? – Kareen Nov 26 '14 at 16:32
  • Yes, that is what I said. – Robert Cartaino Nov 26 '14 at 17:01
  • 1
    @RobertCartaino I'm confused too. You're saying that the turkey is in the danger zone (40° to 140° F) most of the time but also that you have the air (and the surface of the turkey) at a temperature way outside that zone (at least 200°F). I guess you're concerned about the interior of the meat? – Cascabel Nov 26 '14 at 17:32
  • related : cooking.stackexchange.com/q/6446/67 ; – Joe Nov 26 '14 at 22:09
  • I always butterfly turkeys before smoking. They get to temperature much more quickly. – Sobachatina Nov 15 '16 at 22:34
9

This article, by a reputable food scientist, summarizes the possible dangers inherent in slow cooking of turkeys, with some scientific citations and actual experimental data on microbiological growth in slow-cooked turkeys. I'd encourage anyone interested in slow cooking to read it to appreciate the great variety of microbes which could cause problems, as well as the problems that can occur with persistent toxins or spores.

Basically, the take-home message seems to be if your turkey gets to at least 130F within 8 hours and ultimately reaches 165F throughout, it should ultimately be safe, according to the cited research. However, this is of course at odds with official FDA and USDA standards which seemingly recommend less time in the "danger zone" (though they seem to allow some exceptions for food that is smoked or cooked in a pit barbecue in their guidelines, which they sometimes allow to take up to 8-12 hours to attain temperature, and the USDA's own turkey cooking guidelines clearly imply that large turkeys will spend longer than a couple hours in the "danger zone" when roasted at their "safe" minimum temperature of 325F, though other users here have asked them about this, and they refuse to acknowledge that fact when queried).

I explored related microbial issues of slow cooking in my answer to another question, drawing in part on the article I cited earlier. In sum, the official "danger zone" guidelines have lots of built-in buffers to allow for other errors in food handling. Some microbiologists are on record as saying that these guidelines are overly cautious, but exactly how far you can "bend the rules" is not something I want to speculate on.

Obviously, the safest course would be to follow official approved guidelines. I personally had done a lot of research into this before I ever slow-cooked anything myself, and I would encourage others to do the same before coming to their own conclusions. One important thing I would note, however, is that there are limits to slow-cooking safety -- for example, I absolutely would NOT eat poultry that, say, spent a day or more in the danger zone before reaching 130F. Toxins will build up eventually, and at some point even boiling the turkey won't be enough to make it safe to eat anymore.

4

There are basically three primary concerns when cooking your turkey: bacteria, spores, and toxins.

Bacteria: As you point out, since your turkey eventually reaches at least 165 degrees, all the live bacteria will be killed.

Spores: Some of the bacterial spores will not be killed, which means that as the meat cools, they will have a chance to grow again. (Some bacterial spores survive to 212 degrees or higher.) The longer your cooking meat is in the danger zone, the more spores will be produced, and the faster your leftovers may become unsafe to eat. This means that refrigerating or freezing leftovers promptly, and eating refrigerated leftovers soon, is especially important for slow-cooked foods. (Although, having said that, the smoke will act as a preservative, which may counteract this effect. The effects of the smoke may be mostly superficial, but as I explain shortly, so are the bacteria!)

Toxins: Finally, there's the concern you brought up: heat-tolerant toxins produced by certain bacteria while the food is cooking. Even in ideal conditions, most bacteria produce toxins very slowly, usually over the course of days. Most of the time that the food is cooking, though technically in the "danger zone," is not ideal conditions for toxin production. I've seen sous vide recipes that involve cooking ribs for 72 hours, and they remain in the "danger zone" for a significant fraction of that time - they are still considered safe to eat when finished.

Perhaps more importantly, the bacteria come from the environment in which the food has been. This means that on a whole turkey, they will generally be on the surface, which heats more quickly and also dries out first, slowing bacterial growth. In addition, the surface is exposed to air, and most toxin-producing bacteria only thrive without oxygen. This is why toxin-based diseases like Botulism are more likely in prepared foods, where surface bacteria are "mixed in" to air-free (and hence oxygen-free) environments, and usually eaten several days (or, in the case of canned food, months) later.

In short, it should be incredibly unlikely, and maybe entirely impossible, for dangerous levels of toxins to build up in the 12-18 hours that your bird is cooking.

  • I would add a critical safety disclaimer: when you mention a sous vide rib recipe for 72 hours, it's important to note that sous vide methods generally come to an equilibrium temperature MUCH faster due to water circulation. If the water temperature is at least 130F, the ribs will come up out of the danger zone in probably a few hours at most. It would absolutely NOT be safe to dry-roast ribs in a way that took 72 hours for them to get past 130F, and the same logic would apply to other meats, which could begin to accumulate some significant toxins in less than a day. – Athanasius Nov 27 '14 at 5:17
  • @Jefromi, I also have to disagree that "it's never really a concern" about the "interior" of meat. Have you monitored the cavity temp of a bird in a 200-250F oven (the temps mentioned in this question)? I have. It can stay in the danger zone for the majority of the cooking time, despite the exterior surface being hot and safe. Also, add anything to that cavity that might disrupt air flow (even if not fully stuffed) or tie it in a way that doesn't let air circulate, and you have a near-perfect incubation chamber for any interior "surface bacteria." – Athanasius Nov 27 '14 at 5:49
  • @Athanasius When I said interior I meant actual interior, inside the flesh. But the point about the cavity temperature is a good one - I was under the impression that there was enough of an open area on the end of the bird to let things circulate, and that the drippings helped produce some convection in there. – Cascabel Nov 27 '14 at 6:12
  • @Jefromi, yes - comments don't allow full explanation, and I understood you mostly meant interior of the flesh. But you also went onto say "surface (even the inside surface)", which is what I was addressing. Convection can and does help. But from my experience it is possible (particularly in well-sealed electric ovens which don't have very much air motion) for the interior of an open cavity to stay relatively cool for a long time. And if you stick something in there (lemon, giblets, beercan, whatever), even that small amount of convection can be significantly disrupted. – Athanasius Nov 27 '14 at 12:53
  • @Jefromi, FYI - here's someone who did some relevant experiments and measurements, with graphs. You can see a temperature curve for the cavity which shows it often rises slowest of anything in the bird. – Athanasius Nov 27 '14 at 13:02
3

Temperature isn't the only factor in bacterial growth. According to Wikipedia:

A number of wood smoke compounds act as preservatives. Phenol and other phenolic compounds in wood smoke are both antioxidants, which slow rancidification of animal fats, and antimicrobials, which slow bacterial growth. Other antimicrobials in wood smoke include formaldehyde, acetic acid, and other organic acids, which give wood smoke a low pH—about 2.5.

If you smoke your food long enough, you'll also dry it out, which inhibits bacterial growth.

The secret ingredient, however, might be the brine that cooks use keep meat moist. Whether you wet or dry brine your turkey, the effect is the same: salt slows the reproduction of bacteria. It turns out that salt diffuses more quickly when the meat is cooking than when it's cold. So the longer you smoke your turkey, the better preserved it's likely to be. (Also, tastier!)

Anecdotally, I've had no trouble with turkeys that I've brined and smoked overnight. But I did get sick eating smoked trout that was not brined and that I did not allow to smoke the full time.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.