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I'm planning to dry precooked meals with a food dehydrator to make them non-perishable for hiking trips.

Some of the recipes I want to cook do have ground beef, chicken, or salmon in them. I want an estimated for how long they are safe if they were dried for about 24 hours at 70°C (158F).

I plan to dehydrate the meals, freeze them until I go on the trekking trip, and then have the precooked meals in my backpack for the whole duration of the two week trip.

The food during the trip will not be refrigerated, but the temperatures are likely to be between 15°C and -5°C (59F-23F).

  • Out of interest: where did you get the idea of dehydrating cooked meals? – Johannes_B Jul 1 at 7:55
  • The trekking meals you can buy seem to always be dehydrated version of normal recipes and than after finding this youtube video I thought I could do it myself to save some money and be able to choose my own ingredients. – GittingGud Jul 1 at 8:01
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    If they'll keep for two weeks at 15C, they'll keep for much longer and the freezing step is probably unnecessary. If they won't, they won't be safe anyway. I looked at doing something similar and one option is to use jerky, adding it when you reheat. I would use dried soya mince – Chris H Jul 1 at 9:10
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    I don't think it is the proper use of "TL;DR". I am going to edit it out. If someone feels strongly, let me know. I've seen it pop up in a number of questions. It is either used incorrectly, or people don't want to read to gain the information that is provided. In either case, it's probably not useful. – moscafj Jul 1 at 10:21
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    You might also want to take a look at the items tagged 'food' on outdoors.SE for other alternatives : outdoors.stackexchange.com/tags/food – Joe Jul 1 at 12:53
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Dehydrating food is a common practice for trekking and backpacking. Dehydrating vastly reduces the water activity in foods, making them a less hospitable environment for bacterial activity. You'll want to use a reliable dehydrator with a variable temperature setting, as different ingredients require different temperatures and times to properly dehydrate. I think it would be better to dehydrate your ingredients individually, then combine them into meals. For example, Backpacker Magazine has a handy guide with some good suggestions. Dehydrated vegetables have a very long shelf life. From my internet research, it seems that many folks recommend consuming dehydrated meat within two weeks. I'm not sure you want to freeze your products. They might become moist when thawing, thus beginning the re-hydration process before you want. This could theoretically impact safety.

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    Agreed on dealing with ingredients separately ... although I'd also be inclined to buy freeze-fried meats (or things like pork fu), rather than try to dehydrate them myself. – Joe Jul 1 at 12:48
  • @Joe Buying freeze dried meat would be an option but wouldn't achieve the point of having proper self cooked meals on a trekking trip rather than having some jerky. – GittingGud Jul 2 at 5:30
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I am afraid food safety does not work the way you imagine it, or the way that would be easy to deal with. I cannot write up a whole course on food safety here, but here are two facts pertinent to your question.

  1. Shelf stability is a truly binary outcome. Your food either supports bacterial life - which means it is only good for a total of 2 unrefrigerated hours after preparation - or it does not, which means it is good indefinitely and any "expiry" dates are a matter of degrading taste. There is no "slow bacterial growth" state in which the food is safe for several days or weeks or months, but stops being safe afterwards.

There is a bit of an extra twist with all methods that use reduction of water activity to make a food shelf stable (these include dehydration, or jam cooking): since molds need less wetness than bacteria, your food can become unsafe through mold. This is usually not included in safety calculations, you just consider your shelf-stable food safe until you visually see the mold, at which point it is unsafe.

  1. You cannot predict whether a given recipe will produce a shelf stable food. The only way to know is through testing.

It doesn't matter how many parameters you use for the prediction, the process is too complicated to be described mathematically. So any recipe which purports to produce shelf stable food has either been tested "naturally" (by having been used under unchanged conditions for centuries) or in a lab. Note that you cannot make tests for safety yourself - just because something did not make you sick once, or twice, or 100 times, it doesn't meet the criteria for safety.

So, you cannot just pick any food you like, dehydrate it at some temperature, and declare it safe. Nor can you calculate a combination of dehydration time and temperature which is certain to make it safe. You have to find recipes which are either very specific (e.g. someone created a recipe for dehydrated stew that was tested to be safe, and it will have to cover everything including the exact ingredients, stew cooking method, and dehydration method) or apply to a class of foods with known wide safety margin for dehydration (it is pretty easy to make fruit safe by dehydration).

To answer your question directly:

I want an estimated for how long they are safe

The literal answer here is: 2 hours. For any longer duration, you have to use a known recipe that has been designed and tested for safety, and it is impossible to make up that recipe by yourself.

  • You put a lot of effort into writing a detailed answer for which I am thankful for. But your answer did not help a single bit because I ask this question because I know that shelf life/foot safety isn't an easy linear equation. Additionally both your points aren't solid. Food stability is a matter of how fast certain chemical process inside/on the food take place and can be influenced by different environmental conditions. Which makes it predictable and not truly binary as certain exposure to mold/bacteria is safe. – GittingGud Jul 2 at 11:07
  • The problem is that food safety is not a matter of a chemical process. It is a regulatory matter based on knowledge derived from microbiology. Putting up a mathematical model that would predict the growth of bacteria in your food has roughly the same complexity as putting up a weather model that will predict the chance of rain in your city for a certain day - and if you are aware how difficult this is, you will understand why no one does it for food. The answer you are looking for does not exist, that's why I gave you the answer dictated by safety experts. – rumtscho Jul 2 at 11:38
  • Your interpretation of food safety is the legal aspect of it. My interpretation, or my question which is the topic here, is about how long dehydrated food will be good for before I get health problems which can be answered and if you do not know the answer to it than don't answer. I do not want to commercially sell the food I want to eat it while sitting in the dirt on a trekking trip. – GittingGud Jul 2 at 11:45
  • @GittingGud I watched the youtube video you linked earlier. I wouldn't eat the stuff that came straight out of the dehydrator. Certainly not a few days later. Nobody here can tell you if you will get health problems or when. This really is the most sane answer one can give on the internet, which will be read by many people. – Johannes_B Jul 3 at 4:50
  • @GittingGud Again, your interpretation is not answerable. Writing an authorative answer to it will require a long-term research project costing many millions (and still won't apply to a similar problem with slightly different parameters) and any speculation on it is not allowed on the site. – rumtscho Jul 3 at 7:15

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