How to Dehydrate Foods for Long Term Storage

long term food storage, how long does dehydrated food last

The process of dehydrating foods for long term preservation has been used for centuries. I was curious how long exactly, but it seems no one knows, even good ‘ol Wikipedia doesn’t know: http://en.wikipedia.org/wiki/Food_dehydration

There are several methods to preserve food: canning, dehydrating, and root cellaring for some foods. If you’re into root cellaring, here’s a nice quick design.

I will cover canning at a later time so that with this article we can focus on dehydrating foods.

I personally prefer dehydrating over canning for several reasons:

  1. I find it’s much easier than canning
  2. The food shrinks and therefore is more space efficient (water is heavy and takes up a lot of space)
  3. Storing dried food is more flexible
  4. You don’t need to replace supplies, except possibly a dehydrator
  5. Dried food can last longer than canned food

There are some cons to dehydrated food, such as the need for water when reconstituting and eating them. Flavor can also sometimes be better with canning, but that all depends on what foods you dehydrate or can.

First, you need a dehydrator of some sort. A dehydrator with a fan is superior to the “round type dehydrators” without fans, as the fan types provide better air circulation, and will more evenly dry your foods. It’s also nice to have a timer, as over drying can reduce flavor drastically, make your foods look burnt, and also make them harder to reconstitute. But you don’t have to have a fancy electric dehydrator, there are other ways to dehydrate food. Here is a great video on solar dehydrators.

I personally went with a stainless steel model with a fan and a timer because I try to avoid processing or storing food in plastic, and I’m way too busy to babysit my food drying. I like to be able to prep the food, throw it in the dehydrator, set the timer, and forget about it. But everyone has different needs, so choose what’s best for you. I do want to mention however, that electric dehydrators use low heat, and you typically have the biggest harvests in the middle of summer. So you will be heating up your home when it is already hot. Just something to consider.

Okay, now to the fun part: how to actually dehydrate food. First, your equipment must be clean and sterile. Wash everything with hot soapy water, and rinse well. Wash your hands very well. While it’s impossible to have a completely sterile environment in your kitchen, your goal here is to reduce the number of bacteria/yeast/mold that you are starting out with.

The good news is that the method used for dehydrating food also dehydrates the bacteria/yeast/mold, and keeps them from multiplying, which would generally spoil your food. This isn’t to say that you should be careless, but that you don’t have to wear a sterile gown simply just to dehydrate some food.

I personally use disposable gloves. I do so because the act of wearing gloves reminds me to be mindful of what I touch in between handling my food. So it’s more of a way to keep myself alert, and also functions as a way to keep my fingers from putting more grease and dirt on the food.

For the best drying, you want to slice your food to between ¼ inch to ½ inch, unless the recipe calls for something else. Just remember that your drying time will increase the thicker the food is. And if you’re dehydrating tomatoes or other fruits, there’s no reason to include the seeds; best to save those seeds for your garden instead. Also, if dehydrating herbs, leave them on the stem to dry, separate them off the stem after the drying process.

Let’s go back for a minute to the discussion of what the process of dehydrating food actually does. As mentioned earlier, when drying food, you are removing the moisture, which prevents bacteria/yeast/mold from growing on and consuming your food, which is what causes food spoilage. When you remove the moisture, you essentially freeze in time the life process that would otherwise naturally occur, such as the spoiling of your food by that bacteria/yeast/mold that’s present all around us.

However what you don’t stop with dehydration is the natural enzymatic process that occurs in many foods. There is a specific enzyme called polyphenol oxidase, which is found in most foods, which when it comes in contact with air, such as occurs after slicing into an apple, potato, etc., results in your food turning brown. This enzyme is not deactivated when dehydrated, so it still does its job of turning your food brown, just more slowly. Usually there is nothing wrong with the food. But one might develop a mental block about eating something when you can’t tell if it is discolored due to spoilage or due to the enzyme activity. Not to mention that you could potentially be taking a risk of eating food that is spoiled. A final note about this enzyme is that it can also cause to food to taste bad, not just change the color. So it is better to inactivate this enzyme.

For more information on polyphenol oxidase, you can read about it here: http://en.wikipedia.org/wiki/Polyphenol_oxidase

To inactivate this enzyme there are a few different things you can do. Blanching is my favorite technique for leafy greens. Blanching is very simple. Start by cleaning or rinsing off your vegetables, and heat a pot of water to boiling. Once your vegetables are clean and your water is boiling, place the vegetables in a steamer or some type of metal strainer and place the steamer over the boiling water. Your vegetables won’t actually come in contact with the water, just the steam. Put a lid on it, and let it blanch this way for about five minutes (the duration depends on the vegetable/fruit; it is best to follow a recipe here). After the right amount of time has passed, rinse your food with cold water to stop the blanching process. Finally, place your food on the dehydrating tray and put it in the dehydrator. In the photo, I decided to boil my corn instead of steam blanching. You can use boiling as an alternative to blanching if you prefer, but blanching likely retains more nutrients in the food.

The disadvantage here is that cooking food, such as boiling (and blanching is almost like cooking it), may make the food less nutritious. I have not researched comparative studies, so I can’t say for sure. I do know that cooking or blanching the food will definitely change the texture, and sometimes the flavor as well.

long term food storage, how long does dehydrated food last

Blanching my corn by boiling

long term food storage, how long does dehydrated food last

Letting it dry off before putting in the dehydrator

Another method you can use to inactivate the polyphenol oxidase enzyme is to add ascorbic acid, or simply put, vitamin C. There are a couple of ways you can do this. You can buy lemon juice, or you can buy ascorbic acid, both of which are usually in the canning section of your grocery store. I prefer ascorbic acid powder because it’s inexpensive, makes a large amount, stores well for a long time, and doesn’t add as much of a mild lemon flavor to everything. Since lemon juice is a liquid, it takes up more space, spoils faster, and it adds a stronger lemon flavor to all your dehydrated food.

While blanching utilizes heat to inactivate the enzyme, the use of ascorbic acid uses pH to inactivate the enzyme. For more information you can read how it works here: http://everydaylife.globalpost.com/wont-food-turn-brown-put-lemon-juice-it-30073.html

To utilize this method, you simply mix the correct amount of lemon juice or ascorbic acid in the right amount of water (usually 1.5 tablespoons of ascorbic acid to 1 quart of water), and soak your fruit/vegetables for the recommended amount of time (usually about five minutes). Rinse with clean water, and then place on the dehydrator tray.

The disadvantage of using ascorbic acid is that it can also change the flavor of the food. So if this bothers you, this might not be the ideal method for you. You might want to try both the blanching technique and the ascorbic acid technique with a small quantity of food and see which one you prefer before wasting a larger amount of food using a technique that produces results that you don’t care for.

There are other methods of pre-treating food for dehydration, including syrup blanching, honey dips and dipping in fruit juice. I prefer to keep it simple, and keep my calories and sugar intake lower for health reasons. There is actually a wonderful resource available completely for free online. I reference this site for all my food preservation needs and have done so for many years now. Look here http://www.uga.edu/nchfp/ for general information on preservation methods and recipes. The following link is specifically for dehydrating, including other pre-treatment methods: http://nchfp.uga.edu/how/dry.html

When you organize your food on the dehydrator tray, make sure the individual pieces are not touching each other. Do note that the food will shrink, so if you have small food like corn, you might want to use a different tray, depending on the size of the holes in the tray. You don’t want the food to fall through the cracks to the bottom of the dehydrator. There are many options for this, and will vary depending on your dehydrator choice.

 

long term food storage, how long does dehydrated food last

Two trays of sliced tomatoes done

Although I claim to “forget” about my dehydrator, I really don’t. I tend to check on it every few hours, turn the trays around, flip the vegetables so I know they’re not sticking to the tray, and just overall check on the progress. While this is not necessary, it is extremely helpful to do so as your food will dry more evenly and more quickly, and will be less likely to be stuck to the tray when you go to remove it.

The times listed to dry your fruits and vegetables are only a guide. You want to inspect your food to check for complete dryness. Vegetables will be brittle, but fruits will be more like leather. Your goal is to remove the moisture to as low as possible. If your veggies are breaking in your fingers, they are done. And if your fruit is leather like, it is most likely done as well.

If your dehydrator has a timer, then you can just leave your food in there until you are ready to deal with it. But if you are using a solar dehydrator, or other type that doesn’t turn off the heat, then you will want to remove your food as soon as it is dry to prevent over drying.

 

long term food storage, how long does dehydrated food last

I had room for one more tray, but I ran out of things to dehydrate

Once your food has been in the dehydrator for the right amount of time, it is time to store it away right? Well, not so fast. You want to check your fruit for proper dehydration, and to do that, you can do what is called conditioning.

Place your dried fruit in a glass jar, seal tightly, and wait about ten days. Some sources recommend you shake the jar daily to separate the fruit. If you see any condensation in the jar, then the fruit is not yet properly dried, and needs to be re-dried. If there is no condensation, it is ready for long term storage.

long term food storage, how long does dehydrated food lastStore your dried food in a cool room, and keep it away from sunlight. I actually recently discovered that Ball makes dark green jars. I was excited to find them because now less light can get in through the glass jar. It’s a method that’s used for wine and various oils, and it works great. You can also just cover your jars with a towel; that too will keep the light out.

Make sure you label your food with what it is, the date, and I like to add what temperature I dried it at and for how long. This allows me to keep track of what is working and what is not, because as mentioned earlier, recipes are only a guide and may require adjustment as there are many variables that can affect the dehydration process.

This also gives me a little piece of mind when I pick up that food three years later when I’m ready to eat it. This way I know I prepared it correctly. I like to use painters tape to label my jars. I wish I could take credit for this idea, but I can’t; I read it online somewhere and stole the idea immediately. I like painters tape because it comes off very easily when the jar is ready for re-use. I can wash the jar, and there’s no tape glue to mess with, no markings on the jar, nothing. Feel free to steal that idea as well.

Do inspect your foods regularly. Look for mold growth, discoloration, etc. Remember, with the process of drying, unlike canning, you didn’t actually kill the bacteria/yeast/mold. Instead, you deactivated them temporarily by the process of removing moisture. Any moisture that returns will reactivate that bacteria/yeast/mold.

If you do find mold in your jar, get rid of the entire contents of the jar. Do NOT try to cut out or remove the moldy pieces and try to eat the pieces of food that look like they have no mold, as it is likely that most of the food in the jar is contaminated with mold spores, which are invisible to the naked eye and could make you ill.

For long term storage, you can vacuum seal your dried foods. You can also place them in a Mylar bag with an oxygen absorber and vacuum seal that. Then place in a food bucket with a sealed lid.

When it’s time to use your dried food, some foods you can eat right out of the jar. This includes dried fruit. If you make jerky*, you don’t have to do anything special with that either, just enjoy. But when it comes to other foods like corn, greens, and carrots, it needs a little more work.

Personally, I find it best to just turn on my crock pot, fill it with water and bring it to a boil. I then add whatever dehydrated veggies I feel like having in my stew, and let it cook until all the vegetables are soft again.

Some foods, like carrots, you can reconstitute in a bowl of cold water (in the refrigerator though, because you are also reconstituting the bacteria/yeast/mold as well). They are not as crisp as a fresh carrot, but I prefer them over canned carrots.

One of my favorite books with great recipes is Making and Using Dried Foods by Phyllis Hobson But you can also create your own recipes as you go along. Just remember that dried food, when it reabsorbs water, will be a lot more than it initially looks, so be mindful of how much dried food you throw in the pot.

You can also create your own single serving soup by vacuum sealing a mix of vegetables with a bouillon cube. When out camping/hiking, just add hot water and you have instant soup.

Also remember, if eating dried foods without reconstituting, you need to drink more water, as that food will absorb the water in your system when you eat it to help with digestion, so make sure you stay hydrated.

*I want to quickly point out that jerky is made from raw meat, so storage of jerky cannot be very long. It’s best to eat it within six months of storage.

long term food storage, how long does dehydrated food last

Ready for storage

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About Paylie Roberts

Paylie Roberts is the author of the recently published non-fiction book Memories of Poland, Lessons From Growing Up Under Communism. She is also the author of two novels: Bugging Out To Nowhere, and Life After Bugging Out. She has a Bachelor’s degree in biology, and lives with her husband, two German shepherds, and various livestock, somewhere between the Cascade Range and the Rocky Mountains.

View all posts by Paylie Roberts

19 Responses to “How to Dehydrate Foods for Long Term Storage”

  1. Papa J Says:

    After testing for the 10 days, do you vacuum seal the jars? Would this help preserve or be a negative?

    Reply

    • Paylie Says:

      Yes, vacuum sealing the jars will help to extend storage life. You can also use moisture absorbing beads if you don’t have a vacuum sealer.

      Reply

  2. JayJay Says:

    Painter’s tape?/ Another expense??
    Label with a sharpie; remove with acetone or nail polish remover.

    Reply

    • Paylie Says:

      Isn’t acetone and nail polish remover an expense as well? I find that painters tape doesn’t make me light headed when I use it, and it’s quick and easy. But it’s a personal preference.

      Reply

    • Jenna Says:

      Sharpie comes off jars (the glass, not the lid) well with just a good scrubbing and some water too. :) Free.

      Reply

  3. Terry dozier Says:

    love your site, full of great ideas!

    Thank you
    Terry Dozier

    Reply

  4. Diana Says:

    I was hoping you would tell us how long the dried foods (fruits and veggies) would be good for vacuum sealed in jars or in mylar bags with oxygen absorbers. That’s the only info missing from this great article and it happens to be the info I was searching for online.

    Reply

    • Chet Says:

      Thanks for brining that up Diana. Great question and I think totally worth adding to this article.

      Reply

    • Paylie Roberts Says:

      That is an excellent question, and kept out for a reason.

      Unfortunately, without knowing how sterile your dehydrating technique was (did you handle food with gloves? wash with well water or filtered water? Is your well water free of pathogens? What kind of dehydrating unit are you using? Fan type? Turn the round tray type? sun dryer?. etc.)

      The answers to these questions will determine how long your dehydrated food will last.

      Will using mylar bags and oxygen absorbers increase the shelf life? Absolutely. Will these tools increase shelf life in something that was not properly dehydrated? No.

      Fruits and veggies dehydrated in a perfect environment should last a long time, as in years, however, providing such a perfect storage environment can be tricky. Temperature fluctuates and so do the bugs. Sometimes your mylar bag has a leak, and sometimes it’s so perfect you look at food 10 years later and are in disbelief at how perfect it looks.

      My advice? Use your best judgment and rotate your food stock. Number one rule of keeping stored food is to “store what you eat, and eat what you store”. If you do that, you should be rotating your food regularly, and thus not worried about shelf life.

      Second rule to follow is if it smells funny, looks funny, or feels funny, don’t eat it. If that’s all you got, boil it for a minimum of 20 minutes to kill any pathogens, but seriously, if it doesn’t smell like fresh dehydrated whatever when you open the bag, re-evaluate based on what type of food it is.

      Sorry I couldn’t give a more simple answer, but then life has never been simple. The truth is that your dehydrated food storage life will vary from person to person, based on how the food and equipment was handled prior to dehydrating it.

      In a perfect scenario? Several years. But how often do we have a perfect scenario?

      Reply

  5. Katie Says:

    Great and informative article! I was also looking for the information on possible shelf life in the same type of storage.

    Reply

  6. Mary Says:

    I was wondering something, is it necessary for the dried fruits/vegetables to be stored in a glass or plastic containers? Would be a normal sack from a cotton fabric not enough?

    Reply

    • Paylie Roberts Says:

      Yes it is necessary to store your dehydrated food in sealed containers, such as glass or plastic jars, or even zip-lock bags. The reason for this is that food will naturally absorb the water that is in the air around us, and once that water is re-absorbed, it can cause the food to spoil. Some herbs such as garlic do fine in a mesh bag, but only for a short time. If you are looking at long term storage, you definitely wanted to keep your dehydrated food in a sealed container.

      Reply

    • Bill Says:

      Cloth bags defeat the purpose of dehydrating the food. Cloth will let humidity that’s in the air to slowly re-hydrate your foods and increase mold growth also. Plastic and glass are moisture proof.

      Reply

  7. Joanna Cook Says:

    Is it possible to over dehydrate shrimp, meat, veggies? We are dehydrating shrimp, ground beef and turkey for a trip in the Boundary Waters (Minnesota) where we’ll be doing some portage of all our stuff so trying to lighten the load but still have good meals. Should we put what is dehydrated in ziploc bags before vacuum-packing to make sure the moisture is out? Thanks!

    Reply

    • Paylie Roberts Says:

      That is a good question but a tough one to answer.

      Will it kill you? Probably not. Will it be edible? Now that I don’t know, it depends on the food, and how much you over-dry it.

      Over-dehydrating is basically continuing to dry your food after all the moisture has been taken out. What happens at this point is that your food starts to shrink, shrivel, harden, lose shape, and can even lose flavor. if it’s over-dehydrated to the point that it is hard and dry, eating it could be a moot point as it stands a good change that it might not be able to re-hydrate, and will just go through you, thus rendering it useless as a food.

      You also have to remember that when eating dehydrated food, you have to drink plenty of water. The food will attempt to re-hydrate in your system, and so it will absorb the water from you body. If you’re not drinking plenty of fluids, it can dehydrate your body. This is assuming you’re not re-hydrating your food before eating, and it’s not so dehydrated it can’t re-hydrate.

      It is really best to follow the recipe.

      As far as Ziploc bags go, better to just vacuum seal, as Ziploc bags will leave air and therefore moisture. Better to do it the other way, vacuum seal, then put in Ziploc bags as a secondary measure.

      Reply

  8. Elly Says:

    Go to USAEMERGENCYSUPPLY.com
    This site clearly defines the TESTED long-term storage of dehydrated foods. I am an Emergency Management Coordinator and my husband was FEMA. Foods can last much longer than the FDA or co-ops or University Resources tell you. But be careful. There are some great Freeze Dried companies that use no additives or preservatives in their process. Plan for 3 dimensions of shelf life. Canning is shortest term, then dehydrated, then FD. Have at least 3 seasons of food stored, especially now! Hard red wheat, properly stored, can easily last 50 yrs and more likely hundreds. Good luck and be safe.

    Reply

  9. Jonathan Cook Says:

    Hey just wondering, I tend to pre-cook my beef and chicken before I turn it into jerky, as I have IBS and if I don’t I have issues. I know that jerky made without cooking it first only lasts a couple months but how long would you think I could store jerky if I cook it before dehydrating?

    Reply

  10. Jessica Gopinko Says:

    Can we preserve it in vacuum sealed bags? I think it will save more money.

    Reply

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