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I have only recently discovered that cooked food shouldn't be left in room temperature for longer than 2/4 hours.

I lived in a tropical country which is warm and humid and I have been growing up eating left over cooked food(meat, rice, bread, dairy products and left in 30C for longer than 6 hours) with no issues. In fact it's very normal to the people in my country.

So my question is the 2/4 hours only a strict guide for commercial food seller? How come people in my country do not have issues with leftover food? Is this habit a silence killer which only breaks out when we grow old?

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    The rule is less used to say "that and that is unsafe", but "that and that is safe, without having to further look into what the cooked food consists of" for cases (as you said, commercial is an example) where you can't risk being unsafe, or make certain you are safe. At 30°C even shorter times could apply. Bread is usually not considered a perishable food, for meat and rice 6 hours at 30C sounds patently unsafe, same for dairy unless it is intentionally being fermented in a controlled manner. Commented Dec 7, 2015 at 3:22
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    I don't know where you're from, but I suspect the premise in your question is wrong: people probably do get sick from food there. They might just not realize that it's the cause.
    – Cascabel
    Commented Dec 7, 2015 at 6:53
  • The recommendations are based on health guidelines for restaurants -- where they have a much higher risk of problems (more people == more likely to have a person w/ a weakened immune system ... and they risk getting hundreds of people sick, rather than just one family). There are people out there who specifically recommend eating spoiled foods (even meat) as a form of probiotic, but very few people have the stomach for going it with anything other than dairy products (ie, yogurt & cheese). The real risk is botulism -- it doesn't take much, and the effects are nasty.
    – Joe
    Commented Dec 7, 2015 at 11:53
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    If you want to eat food that's been out for longer than 4 hours, that's a risk that you can decide (although, it helps to know what's in the food, to know what the risks are) ... but I'd avoid serving food that's been left out for long periods to other people, as they might have a compromised immune system or other issues that increase their risk. Of course 'long' is likely as local determination, as it's possible that people in your region are better able to handle the bugs in your area, and that Americans have weak immune systems from over-hygiene.
    – Joe
    Commented Dec 7, 2015 at 11:59
  • @Joe Botulism is not an issue here because the food is not kept under an airtight seal. Clostridium botulinum is strictly anaerobic which is why it is a preserved-food issue. Commented Jun 11 at 12:28

4 Answers 4

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The food safety guidelines are based on scientific & mathematical calculations along the lines of:

Given an initial bacteria count of X they will under the given conditions mulitply to a number of Y amd have produced Z [unit] of toxins.

Now what to do with these values?

We use them like seat belts or helmets. Not wearing a seat belt will not automatically kill you, only if you are involved in an accident you are much more likely to suffer severe injury or death without it. Still, nobody could responsibly recommend ignoring a seatbelt, knowing that accidents do happen. But with food safety, many are willing to skip their seat belt, so to speak.

One very common misconception is that contaminated food can be detected by smell, looks or taste. Yes, some kind of spoilage is obvious, but many, especially the more dangerous ones, are not "visible". One very prominent example is Salmonella. Note that many toxins are not destroyed by cooking, more details in our canonical post.

I can guarantee that people in your country have issues with cases of foodborne illnesses - all countries do. You need to keep in mind that

  • Foodborne illnesses need not become apparent immediately or shortly after a meal. The symptoms of Salmonellae, for example, might start as late as 72 hours after infection. It is likely that the connection between a sudden bout of sickness and a meal eaten three days prior is simply overlooked.

  • In healthy adults infections may pass unnoticed or cause only mild sympotms like indigestion. The human body can handle a certain amount of bacteria or toxins, the individual levels of tolerance vary, though. So children, elderly people or those with a compromised imune system are more likely to suffer and have a higher chance of severe complications or death. The given safety guidelines are calculated to protect these groups as well. Also note that often the side-effects are as dangerous as the pathogens themselves, diarrhea being a classic example.

  • There is no way of determining the amount of bacteria present in a specific dish, piece of meat or other food prone to spoiling - unless you get a lab involved. The values used to calculate safe thesholds contain a certain safety margin. Your dish could contain fewer bacteria to start with or if any were present, they might not have multiplied that much. (But they might as well have, we can't safely know.) The two/four hours rule simply means that the food will remain in the safe range, not that it will be spoiled afterwards.

So what now?

It is entirely up to you to whether you choose to drive with or without seatbelt or helmet. Make an informed devision and consider the welfare of those weaker than you. What you as a healthy adult can stomach (pun intended), might be fatal to a young child or weak elderly person.

Only a few days ago the WHO published a news release on foodborne diseases:

  • First ever estimates of the global burden of foodborne diseases show almost 1 in 10 people fall ill every year from eating contaminated food and 420 000 die as a result
  • Children under 5 years of age are at particularly high risk, with 125 000 children dying from foodborne diseases every year
  • WHO African and South-East Asia Regions have the highest burden of foodborne diseases

(Source)

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    In fact, driving without a seatbelt/helmet is pretty common in tropical countries :D
    – user280593
    Commented Jan 18, 2017 at 20:14
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Yes, that's generally thought to be true — as determined through the science of modern food safety. You can read about specific guidelines on the Food-Safety tag wiki. Those practices were developed as broad recommendations, usually erring on the side of caution.

That being said, you might be able to get away with it sometimes, without dying of food poisoning, but it could be risky. Much depends on the food itself — bread left at room temperature may last for days, but you could have problems with meat or dairy products after just a couple of hours.

Bacteria and other harmful pathogens can exist everywhere. At room temperature, those organisms can multiply very rapidly, producing toxins that can make you sick. You can NOT rely on smell to detect them — food can be highly infected, but smell and taste just fine. That's why, for safety, it's important to refrigerate or freeze cooked food to slow down the growth of any pathogens.

It's best to do this as soon as possible after the food cools down to room temperature. You also want to avoid putting hot food directly into the refrigerator because it may heat up the 'fridge, affecting other food inside, and actually delay your food cooling down to a safe temperature.

Food poisoning isn't something that only breaks out when we grow old, though elderly people, young children, and those with weak immune systems can be more susceptible.

As leaving cooked food at room temperature was "normal" in your country, I wonder if there wasn't also a prevalence of food poisoning that was also just considered "normal'. How often did people have upset stomachs or diarrhea, and just accept it as part of everyday life?

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    This is a good answer. The only point I'd note is that if you're following recommendations from most food safety organizations, you shouldn't wait until the food "cools down to room temperature." Once it gets under about 130-135F, bacteria can start to grow. Most modern fridges won't warm up appreciably if you put hot or warm food in them, and most food safety organizations recommend refrigerating earlier rather than cooling to room temperature first. You obviously just want to keep any hot food away from highly perishable foods (e.g., raw meat) in the fridge.
    – Athanasius
    Commented Dec 7, 2015 at 18:26
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    Your first and second paragraphs are actually saying the same thing. What's true is that it's dangerous to eat food that's been out that long, where "dangerous" doesn't mean "you will get sick" (a common misconception) but rather "there is significant risk of getting sick." Presenting them as a contrast like that might encourage the misconception.
    – Cascabel
    Commented Dec 10, 2015 at 20:10
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Here is a general consideration which seems too long for a comment.

Almost all regulations (electrical code, aviation checklists, FDA approval for drugs and devices etc.) are "written in blood", i.e. have been enacted in response to preventable damage to property or people.

The safer our lives become in general, the less tolerant we become towards preventable risks, and the stricter regulations become.

Before the advent of antibiotics, vaccines and generally sufficient nutrition, there was a low but constant mortality even among young people. You could die from a tetanus infected wound or any number of other severe infectious diseases. Children died from fevers. And some young adults would die from work accidents, and a few from botulism, and a few more old ones from salmonella infections.

But during the second half of the 20th century, medical progress achieved the incredible: Almost no healthy, young people die from illnesses any longer.

This leads to an effect known from cleaning a kitchen, or from optimizing computer programs: What counts as an issue is relative. After I clean the really dirty parts there are still parts which prevent the kitchen from looking clean, parts I didn't even notice before. In my computer program, after I optimize away the really slow parts, there is now something else responsible for keeping the program running as fast as it could.

The same effect exists in public health: Policies are always aiming to eliminate the largest risks. With ongoing success, even these largest risks become smaller and smaller in absolute terms. For example, every jar of honey sold in the U.S. or EU carries a warning that it shouldn't be fed to infants even though fewer than 10 infants die from a Botulinum infection each decade. The condition was not even known before 1976. The campaign may have saved about three infants in the U.S. per decade. I'm recounting this to illustrate the efforts we as a society are willing to make to save lives whose loss is entirely preventable.

This trend over time leads to especially older people shaking their heads at perceived overregulation because they have a lot of first-hand experience that things work as well, and much easier, without it. This argument suffers, obviously, from survivor bias; perhaps more importantly, the personal anecdotal evidence is not applicable to the entire populace and all circumstances. As with airplane accidents which only happen due to a confluence of several things going wrong, food that's been out for four hours will only make susceptible people sick when the ingredients were carrying an unusual bacterial load, it was a cooked a bit shorter, the room was a bit warmer, there was a little less vinegar in it and your grandmother felt a little weak that day to begin with.

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As long as your immune is strong you don't need to bother about temperature of the food storage and time. Because I saw the poor young and old people and dogs sharing their food from the wastebin but not get sick. God gives them special immunity to sustain this. But the more hygienic people get sick easily with foods.

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  • Immunity (which certainly is stronger among people regularly exposed to a pathogen) is usually acquired through infections. Only some of those may have been subclinical. The other ones made the people sick, sometimes seriously or even fatally. The lack of immunity is the result of avoided illness and death. Commented Jun 15 at 10:27

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