In my last article, “Tasty Alternatives to Freeze-Dried Trail Meals,” I advocated getting busy over the winter season to prepare your next season’s backpacking dinners using your favorite home comfort-food recipes and some simple methods with a home dehydrator.  When we talk about this in my backpacking food prep classes, many of my students ask about how to store their dehydrated food safely over the intervening months.  The following information and guidelines come from my own research, experimentation and some very helpful consultation with Margaret Veibrock, Director of the WSU Extension for Douglas County Washington and a real expert on the subject. Bottom line: Food drying is a centuries-old method for safely preserving food and as long as the food is fully cooked to at least a minimum germ-killing temperature in advance, taken quickly down to a very low water content and kept dry and uncontaminated during handling or storage, the risk of pathogen growth and resulting illness is very low.

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The available research on home dehydration is focused on fruits, vegetables and some types of meats, rather than whole meals.  However, the considerations for safe storage of home-dehydrated meals are not that much different, except it is a low-acid pre-cooked mixture, and as such, it needs to get dryer than fruit products.

Some basic guidelines:

  • Be sure that your food is thoroughly cooked before putting it into the dehydrator – that is, that you’ve heated it even at the center to at least 200 degrees and held it there for ten to fifteen minutes.  Don’t put food into the dehydrator that has sat out on the counter cooling for hours or in the refrigerator for days.  If you have a leftover meal that you decide to dehydrate a few days after you originally made it, re-heat it thoroughly first.
  • Make sure all the cooking, pureeing and spreading out are done in very sanitary conditions – thoroughly wash and disinfect the food processor, dehydrator trays, countertops and cutting boards, any utensils and your hands before handling the cooked food.  Even after cooking, food could be re-contaminated with Staph or other harmful bacteria as it is pureed and laid out on the dryer trays (surface as well as hand contaminants).
  • Food dehydration works as a safe food preservation method by controlling water content, which in turn controls bacterial growth.  So a key to safe storage of home-dehydrated meals is to bring the water content of the food down quickly to below 10%.
    • There is no standard guideline for how quickly the water content of your dish will be reduced to the target moisture content – each mixture will vary.
    • The smaller the pieces in your mixture, the more quickly it will dry.  (and the more quickly it will rehydrate at camp!)

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    • It’s critically important to spread out the food evenly in a very shallow layer on the dehydrator tray to aid rapid drying.  Don’t overload the dehydrator with wet food – this will slow down the process.  I usually try to keep an empty tray between each of my full trays.
    • Use the temperature settings on your dehydrator – in particular, use the 165 degree setting for any meat or egg dishes or dishes with a higher fat content.  Use a food thermometer to check whether your dehydrator is actually getting to that temperature with food inside.  Putting hot food into the dehydrator will help it maintain temperature.  You can reduce the temperature to 145 degrees for vegetable dishes, and should go even lower for fragile foods like mushrooms or herbs.

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    • After a couple of hours in the dehydrator, stir the food, flip the pieces over, crumble up clumps, rotate the trays, move food from the solid plastic trays to the mesh trays (remember, clean hands and utensils!).  If it’s just not drying, your dehydrator may be overloaded and you may need to take one of the trays out or remove some of the food.
  • The product is not fully dry and ready for storage until it is crispy-crumbly, brittle.  Test it for brittleness (or, for fruit, lack of stickiness) after fully cooling the food.
  • Once the food is crispy dry, cool it down fully before packaging. I use zip-loc bags, with a label in the bag naming the food item, the number of servings and the date it was packaged.
  • I also recommend packaging your meals in single-meal servings – that’s two servings if you’re bringing a meal for two, one serving if you’re cooking ‘solo’.  Every time you open a bigger bag to fish out a serving, you create an opportunity for new germs and moisture to get into the bag.
  • If the product is crispy dry when taken out of the dehydrator, and kept from re-absorbing moisture in the packaging, it can be safely stored for months in a cool place (big closed bin in the garage) or in your freezer.   I keep a stash of dessicant packets handy (can buy in bulk on Amazon!) to toss into each bag and absorb any stray molecule of moisture that might have wandered in.
    • References vary in their statements regarding the length of time that dehydrated food can be stored safely.  I have successfully kept food, even foods containing meat and eggs, crispy-dry and tasty for as much as a year, and certainly four to six months is safe as long as you ensure that the food stays dry.
  • Nasty germ spores that might have survived in the food after cooking are not a big concern due to the open air nature of the drying (anaerobic – i.e. low-oxygen – conditions can foster growth of some nasty pathogens), as long as the food remains very dry through storage.  Check the food periodically during storage to make sure that it has remained crispy-dry.  If it appears to have gained moisture in storage, put it back in the dehydrator, cool, rebag and put it back into storage.
  • Treat any rehydrated food as perishable. Once the food is rehydrated, it requires refrigeration to control pathogen growth. Any leftovers should be discarded.
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