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I've recently started using a slow cooker and I was thinking about recipes that could be cooked for days. My main concern is if there are any side effects for leaving food cooking for days that would make this plan unfeasible (dangerous to try). Since it is at cooking temperature, there wouldn't be any reason to worry about bacteria growing on the food. Liquid would be lost over time, which could result in burning if left unchecked, but if I add more every morning/night as needed, that too wouldn't be a problem. All I can see is that most recipes wouldn't end up tasting as well, but undesirable isn't equal to dangerous.

There just seems to be something absurd with the notion of leaving food cooking for 5 days or even 2 weeks without there being any dangers, but I'm having a hard time figuring out what they would be.

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You've answered the food safety question yourself. So why would you want to leave anything cooking in a slow cooker for five days or two weeks? It is kind of absurd. –  Carey Gregory Oct 1 '13 at 3:46
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Who would want to eat a century egg or fish that hasn't been thoroughly cooked? What about fried tongue or 'milk' from almonds/soy? What you or I call absurd another may call dinner. Beans that turn to mush? Perhaps that is a new food or part of a new dish? Perhaps something too woody to eat right if cooked regularly will soften and become edible when cooked this long? I'm not saying it will end up with something worth eating, I was just wondering if it could safely be eaten. –  Lawtonfogle Oct 1 '13 at 13:05
    
@Lawtonfogle Century eggs aren't made like this. Eggs or fish cooked for hours (let alone days) will be overcooked. If you're going to cook something this long there's not much point frying it, and if you're just trying to soften it up before frying, it doesn't take days. And if you want mush, you can generally get it with a few hours of cooking (at most half a day) and a little mashing. I'm not saying it's useless, but the real uses for cooking this long are fairly limited. –  Jefromi Oct 2 '13 at 1:07

3 Answers 3

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It's safe. All that matters for safety is that the food stays out of the danger zone (above 140F).

But it sounds like a pretty reliable way to overcook things. Perhaps that's why it sounds absurd to you? Slow cookers tend to be somewhere between simmer and light boil (probably at least 180F), and there's very little that won't be fully cooked after half a day at those temperatures. If you cook for days, you'll start turning beans and vegetables to mush, and may manage to make meat tough from overcooking. So at best it's pointless, and at worst it's going to mess up your food.

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Additionally, the longer the food is boiled, the more of its aromatic flavor compounds will be lost due to evaporation leaving. Even overcooking just a few hours at a simmer can lead to muddy, dull flavors... –  Didgeridrew Feb 25 at 19:41

What you're suggesting was effectively a form of food preservation in medieval times -- just keep the food warm at all times.

This works best if you keep adding something to it (not just liquid), so there's something that hasn't completely turned to mush ... and you might want to hit it with a shot of vinegar or citrus to perk it back up when serving. You can also add acid while cooking to slow down the breakdown of potatoes and onions (and maybe other vegetables), but in the long-cooking you'll lose some of the brighter notes.

If you try it with stew, you're going to end up with something closer to ragù by the time you're done. Personally, I like that in a pot roast, but I know some people aren't fans.

You could also add some fresh, mostly uncooked items when serving, that just need to be warmed through. (eg, fresh or frozen peas (not canned), been sprouts, or some diced bell pepper or onion, as appropriate for the dish).

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The technical answer is, as long as the food stays above 140 F / 60 C, pathogens are not going to grow. This is the hot equivalent to refrigeration. Note that there are probably no studies of holding foods at these temperatures for truly extended periods, but you pays your money and you takes your chances.

On the other hand, even with the lid on, over time, water is going to escape, and the food will begin to dry out. Even slow cooking meats like pork shoulder or ox tails can and will become overcooked and tough over time, even if there were no moisture loss.

With the fringe exception of a stock pot that is continually replenished, I cannot think of a single good reason to do this.

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Even with refrigeration, a lot of food spoils after a few days. Could the same happen if you are keeping it hot? –  Lawtonfogle Sep 30 '13 at 17:56
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That is the part where I doubt studies have been done, but since the idea is so absurd already for reasons both Jefromi and I have enumerated, I am not going to go looking for any such science. –  SAJ14SAJ Sep 30 '13 at 17:58
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@Lawtonfogle Things can grow at refrigeration temperatures; they just grow more slowly. Things can't really grow at cooking temperatures (though some things can survive, they don't keep growing). –  Jefromi Sep 30 '13 at 18:08
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@lawtonfogle It'll spoil from over-cooking, if you're keeping it hot for days at a time. Shouldn't be any bacteria though. –  Satanicpuppy Sep 30 '13 at 18:08
    
In China my friend told me they do this over the whole winter in some regions. Just add new stuff everyday and keep it hot. –  vwiggins Oct 1 '13 at 11:26

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