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does cooking kill bacteria? [moved from Home Cooking]

  • t

I did the dumbest thing--left out a baggie of chicken thighs to defrost and forgot to put it away when I went to bed. It was out about 8 hours. Still cool, but not cold. House temp was 68 degrees.

I'm going to toss it, it's only about $1.20 worth of chicken.

But does cooking kill any baddies that might have grown in it while between 40 and 68 degrees? The science part is what I'm looking for..Have checked other posts and they range from 'go ahead and cook it' to 'no way', but no science. I checked out CDC website and they were not clear as to the science. They were discussing salonella, but mostly in uncooked eggs.

Food Scientists out there?

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  1. No food scientist here, but I have "enjoyed" the Bad Bug Book at the link below. Lots of info. I believe that although heat will kill most bacteria, the toxins they may produce, may NOT be killed by heat.

    BTW, I leave stuff out overnight to defrost all the time, on purpose.

    Link: http://vm.cfsan.fda.gov/~mow/intro.html

    2 Replies
      1. re: danna
        bruce in oakton

        I grew up in New Zealand in the 1940s and 50s. Until the late 50s MOST people did not own a refrigerator or the item Americans quaintly referred to as an 'ice box'
        My parents had a cupboard on the shady side of the kitchen with a mesh-covered window frame on the outside wall. In addition, all shops closed on Friday night and nothing could be bought until Monday with the exception of a couple of perishables such as milk and possibly eggs. The meat for Sunday's roast had to survive unrefrigerated in these circumstances and, in fact, its cooked leftovers were still consumed in various ways during the week. Meat was mostly Beef, Lamb or Veal - Pork tended to be eaten only in the cooler months and because of the absence of factory farming, chicken was an occasional treat.
        Butter was always soft; if jam grew mold you just scraped it off. Meat fat was poured off and saved in cans, in the aforementioned cupboard to be used for frying.
        The summer temperatures were often in the 80s but I don't recollect anyone in my family (or anyone elses) coming down with food poisoning.
        When we finally could afford a refrigerator it was celebrated as a means of having really cold drinks and ice cream etc on hand first, and long term food storage second.
        As most people in the world have had to get along without refrigeration until about 50 years ago, one can only assume that the toxicity cited so often is due to the way the food is now produced and processed.

      2. It'll kill the bacteria (salmonella kicks the bucket at under 140ยบ), but it won't do a thing for any toxins that may have ensued from bacterial growth. However, my choice in this case would be to go ahead and cook'em, but then I'm the kind of nutcase that makes his own mayonnaise with raw eggs, too...if that is any help at all.

        4 Replies
        1. re: Will Owen

          For any other kind of protein I'd agree and cook but there is something about chicken that makes if go off so easily. Did it pass the sniff test?

          1. re: Homer J

            Btw, this is also true of grains, especially rice. Bacillus cereus is a major cause of the food poisoning people assume is from flesh but is actually from grains that have been left out too long at room temperature and allowed spores to produce toxins that will not be deactivated upon recooking. But a lot of people assume it's the meat that caused them to get sick when it was something as innocent looking as fried rice....

            1. re: Karl S

              I'm sure you are right but I cannot tell you the hundreds of times I have eaten rice that was left out over-night with no ill effects.

            2. re: Homer J

              I didn't sniff it- I've already tossed it.

              Just wondered about heat and toxicity.

          2. Any bacteria will likely start on the outside and work its way in as the meat defrosts so simply rinsing the piece of meat can wash away the surface toxins. I've watched other home cooks prepare chicken straight out of the package and that worries me.

            2 Replies
            1. re: D.T.
              Brian Lindauer

              Actually, the USDA recommends against washing raw chicken because it doesn't do anything except spread bacteria to other parts of your kitchen. See the Cooks Illustrated link below.


              Link: http://www.cooksillustrated.com/askco...&

              1. re: D.T.

                To paraphrase Jacques Pepin, there's no sense washing chicken...any bacteria that can survive a 450F oven for 30 minutes deserve to live!

              2. IMO, $1.20 isn't worth the pain and suffering you'd experience if you did get sick. I left some cooked eggplant out a few nights ago (see thread below) and am still hesitant to eat it, tho I'm sure it's a lot safer than uncooked chicken.

                1. And still all you got was a bunch of "this is how I feel posts." My favorite is the poster who is upset with home cooks that make chicken right out of the package, as if rinsing under cold water does anything to kill pathogens in chicken. Chickens should, never, ever be rinsed before cooking.

                  Here's your science. All those organisms are killed when exposed to 141 degrees F for one minute. Since you're cooking your chicken at a much higher temp for a much longer period of time, your food is safe. Bacteria love temps between 40 and 135. There are good and bad bacteria and they die at higher temps and may go dormant at lower temps. Beware of cooked food that is cooling down as bacteria can again be breeding. If you intend to refrigerate leftovers, you want to get them below 40 degrees ASAP so that the bacteria has as little time as possible to reproduce. Leftovers reheated in excess of 141 degrees F for more then one minute will again kill any pathogens. Foods with a low pH (high acid content) are also safe as bacteria cannot exist in that environment.

                  You are smart to be concerned about food safety. Be conscious but not paranoid. Refrigeration is a very modern invention and mankind did pretty well for centuries before it existed.

                  3 Replies
                  1. re: dk


                    Yes, I tend to be a little casual about popping my leftovers in the fridge right away. (I like the idea of using an ice water bath to cool them quickly, but alas, no icemaker!)

                    Thanks for your post which shows me I need to be using my Polder themo to read reheat temps. I mostly nuke to reheat and need to be maintaining the 140 mark for a minute, so I'll pay attention to that.

                    Much obliged!

                    1. re: dk

                      Yes, and I agree the chicken in this particular case would almost certainly be perfectly safe, but earlier posters who mentioned that killing the bacteria does not necessarily destroy any toxins that may have been produced by those bacteria are also correct. However, for that to be a problem the bacteria must have had time to multiply and build up the concentration of toxins, which is extremely unlikely in an overnight defrosting (something I do all the time, and have [so far] survived).

                      1. re: FlyFish

                        Indeed. Which is why you can't just leave raw chicken out on, say, a 90 degree day for 12 hours, and then just cook it, on the theory that the cooking will kill all the bacteria anyway.

                        A rather important question of science, that.

                        Link: http://seasonalcook.blogspot.com

                    2. For a more complete scientific response, comprehensible to this non-scientist, I recommend FOUNDATIONS OF FOOD PREPARATION, a college textbook written by Freeland-Graves/Peckham. The entire chapter on Food Safety, pg 92-109, discusses molds, bacteria & toxins of differing varieties.

                      Harold McGee's revised ON FOOD AND COOKING touches on this as well.

                      2 Replies
                      1. re: Sherri

                        There's a researcher that went further away and gathered ancient known herbs and the safer materials that won't get you sick even on a long term period (e.g. by polluting your body) and wrote a book to prevent all diseases safely and affordably. She was Hulda Clark, and despite her cancer cure research caused lab mobs to get her attacked for many reasons (e.g. prescribing spices and herbs to cancer patients without an MD degree) her descriptions of illness process and pathogen killing with herbs are never found fault on by pathologists.
                        You can find her books for free (she donated the rights to the people) online, and you'll find a solution for every food and chemical in water and daily products that could make you sick.
                        I never thought I would be preaching a book other than the bible, but after seeing how she was attacked while admitted she was not wrong, while labs do... well, what we know they do, money... I just can't stress enough: Read them and pass them on to your loved ones. "The cure for all diseases" and "The cure for all cancers".
                        you'll find some herb or method to prevent and counteract any food poisoning you could expect.
                        Good luck.

                        1. re: Hardseed

                          Physician, heal thyself. Yet with all her "treatments", she was unable to cure herself, and died of multiple myeloma. Sadly, not before she convinced many other desperate people to forgo proven conventional therapies to try her quackery.

                      2. thanks to you all for the science lesson!

                        1. t
                          the operon script

                          Hi - I'm a microbiologist and I have taken several food microbiology courses, so I thought I would offer my 2 cents.

                          Does cooking kill bacteria? Yes... but not completely. Bacterial populations are extremely large, so the best way to consider them is to look at how many logs of bacteria are present per mL or per gram (e.g. 1000 = 3 logs, 1 million = 6 logs). Cooking reduces the bacterial load in meat by several logs but does not kill all of the bacteria. If you start with 8 logs and reduce the population by say 4 logs, you are still left with 10 000 bacteria, which might be enough to make you sick! Foods of all kinds have different bacterial populations (pathogenic and non-pathogenic) associated with them and most of the pathogens you might cultivate in your kitchen will come from the food itself. Often they are present in fairly low numbers and the population is reduced to essentially nothing or a low enough dose not to cause an infection by cooking.

                          The problem with leaving food out is that the population of pathogens can replicate to high enough numbers that there are still enough survivors to cause an infection after cooking. As an aside, the types of temperatures and pressures used in canning, however, are effective at killing "all" bacteria (i.e. they reduce the potential bacterial load of the most heat-resistant bacterial standards by 13 logs, which is more than enough for foodborne pathogens). In fact, it is the same technique used to sterilize medical equipment!

                          But each kind of food has different types of pathogens and each type of pathogen has a different infectious dose and method for causing illness, which is why it is hard to make a judgement call on whether it is safe to bend the rules about food handling for a particular food item. Also, the relative health of the person eating the food will play an important role in whether they get sick or not. Taking antacids, antibiotics, immunosuppressive medications, etc can make a person more likely to get ill - a bacterial dose that would not affect a healthy person could affect someone in the aforementioned situation.

                          When it comes to chicken, there would have mostly Salmonella and Campylobacter on the surface in a fairly high population (unless it is mechanically de-boned, in which case they may be inside the meat too) and since the skin gets the hottest during oven cooking, they will be reduced to a very low level if the meat is cooked properly. Hence the reason for not washing chicken, as previously mentioned - these bacteria could be spread to other foods that will be eaten raw, like vegetables for a salad. As to whether all the bacteria will be killed by cooking after sitting out on the chicken overnight or not, I don't know, as it depends in the initial bacteria load and what temperature the meat was stored at.

                          The previous comments on toxins in foods like rice is very important too - in this case, heating followed by keeping the rice warm results in the formation and release of toxins that cause food poisoning, even after the bacteria that made the toxins have died. Just to complicate things, some toxins are heat stable and others are not, so sometimes reheating the food destroyes the toxin but not always. Dairy products are more likely to have Staphylococcus aureus heat stable toxins, etc. But I don't think there are many toxin producers associated with chicken, so that shouldn't be a factor here.

                          I can say from personal experience that anything left out overnight is going to start growing bacteria, and something that may be present in low enough levels that it can't cause an infection can multiply to the point where it is capable of doing so. Case in point: I gave myself a very unlpleasant 4-day gastrointestinal infection by pressing tofu on the counter overnight (rather than the recommended 2 hours). Given how unpleasant these infections can be and the small but significant risk of complications, I would err on the side of caution and toss it, as you did.

                          Cheers and safe cooking!

                          3 Replies
                          1. re: the operon script

                            Just wanted to thank you for this generous explanation, though I'm not the OP. And to ask two more questions for whomever might still be following this thread:

                            1) If "heating followed by keeping the rice warm results in the formation and release of toxins that cause food poisoning, even after the bacteria that made the toxins have died" (quoting operon script): is the best practice to refrigerate uneaten food ASAP (i.e., when still hot) after cooking? What's the difference if that food then cools down very slowly in the fridge, thus undergoing a period of warmth during which bacteria have time to reproduce?

                            2) dk write: "All those organisms are killed when exposed to 141 degrees F for one minute. [...] Beware of cooked food that is cooling down as bacteria can again be breeding." Where are those bacteria coming from if they've already been killed?

                            Thanks in advance. I find a lot of this quite confusing and would like to get clarity, especially as my cold-weather cooking habits will soon have to adapt to summer heat and might sometimes forget to.

                            1. re: sequins

                              #1. The point is to get it to a safe temp as quickly as possible, counfounded by the fact that putting something hot into your fridge raises the temperature inside the unit and thus possibly raises the temperature of everything inside to a less than safe level for a period of time. On both points this is a bigger issue with large things.
                              #2. From handling, utensils, etc. Or, as was pointed out in the previous post, cooking only significantly reduces the level of bacteria. It's never going to be sterile.

                            2. re: the operon script

                              Well said! Thanks so much for taking the time.

                            3. I read this thread to find out how to treat a rice dish I planned to take to a social event. Now I think perhaps I shouldn't be taking it all. And - I was very disturbed after reading the very thorough explanation provided by the microbiologist. My husband developed Guillain Barre syndrome after a severe bout with food poisoning. He became totally paralyzed within a day, was hospitalized for 5 months, came home in a wheelchair and two and a half years later is only about 80 percent recovered. The primary cause of this auto-immune response is campylobacter jejune. I convinced myself that my husband caught it off eggs of the chickens we kept. Now I'm afraid it might have started with chicken that I didn't prepare properly. Having experienced this - I can't emphasize enough that it is not worth the risk to eat any questionable food!