Freeze drying food seems like space-age technology, but the practice of freeze-drying food actually predates electricity. There are a few different ways to freeze dry food at home, both with and without a freeze-drying machine.
I’ll walk you through all the options for freeze-drying food at home and the pros and cons of each method.
Freeze-dried food is making its way into more grocery stores and home pantries than ever. Contrary to what you might assume, most people don’t use it as lightweight camping food, and most average suburbanites aren’t hoarding it in back closets. (Though if 2020 taught us anything, it’s that having emergency food on hand isn’t a bad idea.)
Believe it or not, most people that buy freeze-dried food at the store are just using it for everyday meals…because it’s tasty.
A few decades ago, freeze-dried food was only sold as a novelty, and I remember my parents buying me freeze-dried astronaut ice cream at a ball game as a kid. Everyone got a kick out of it, and though it was tasty, no one took it seriously.
Who needs freeze-dried food besides actual astronauts?
Fast forward a few decades later, and freeze-dried food is incredibly popular with regular home cooks, and parents are tossing handfuls of freeze-dried fruit into their kid’s lunches as a special treat.
Trader joes sells packs of freeze-dried food right alongside their dehydrated banana chips and raisins. And most grocery stores carry freeze-dried strawberries, raspberries, and other fruits because they’re used by so many bakers these days.
They add incredible flavor to baked goods without the moisture that makes muffins, bread, and cookies soggy.
Freeze-dried food holds its shape and quickly rehydrates without losing the flavor, texture, and appearance of fresh food.
On the other hand, Dehydrated food loses its shape and develops a rubbery texture that won’t rehydrate nearly as well. Since it’s heated as it dries, some of the sugars carmelize in fruit, and meat, cheese or egg proteins change, meaning that it’ll never be the same again.
Though freeze-dried food is delicious and handy to have in the pantry, both for everyday cooking and emergencies, it can be expensive. I’ll walk you through different ways to freeze dry food at home, from the traditional methods used in the Andes to freeze-dry potatoes to home-built options, and finally, small freeze dryers for home use.
I’ll be honest, using an actual freeze dryer is by far the best option, and though they’re an investment, they should pay for themselves in less than a year of regular use.
How does Freeze Drying Work?
Freeze drying is a way to dry foods at low temperatures. In a home freeze drying machine, the food is frozen, and then a vacuum pump lowers the pressure in the chamber. At low pressure, ice turns to gas in a process known as sublimation.
Early in the process, the ice acts as a scaffolding to help the food hold its shape and texture during the freeze-drying process. Later on, once all the water has been removed, the food still retains its shape, size, and texture.
Freeze drying also happens occurs in nature, outside of a vacuum chamber.
In the arctic, animals like seals and penguins that die are sometimes naturally freeze-dried as arctic winds first freeze and then slowly dry the meat. It’s an archeological phenomenon, but the preservation works the same way, and specimens are preserved indefinitely.
Humans also freeze dry food, and the tradition goes back to the pre-colonial period in the Andes, where potatoes have been freeze dried for at least a thousand years.
What’s the Difference Between Freeze-Dried and Dehydrated Food?
Since freeze drying works at low temperatures, sugars and proteins within the food remain unchanged. Add water, and they’ll rehydrate easily, and the food will taste more or less as it did before freeze-drying.
Dehydration relies on heat evaporation of water, and that heat changes the food in the process. Sugars in fruits slowly caramelize, proteins slowly cook (or overcook if they’re already cooked), the food shrinks and takes on a rubbery texture.
Some foods rehydrate well after dehydration, like dried carrots. Other foods don’t dehydrate well, and they won’t ever be the same.
Freeze drying, on the other hand, works well for just about any food. Anything from freeze-dried meat to Freeze-dried fruit, even freeze-dried cheesecake…it’s all delicious.
The only things that don’t freeze dry well are very high fat or high sugar foods that are low moisture anyway. Things like peanut butter, chocolate, and honey. Those happen to have a long shelf life on their own, so freeze-drying isn’t really necessary anyway.
How Long Does Freeze-Dried Food Last?
While dehydrated food tends to last 2 to 3 years at most, freeze-dried food maintains peak quality for decades. If stored properly, freeze-dried food should be unchanged for 25 to 30 years, perhaps longer.
I had the opportunity to test this when I bought a few “antique” cans of freeze-dried food at an estate sale. When I opened the sealed no. 10 cans, the freeze-dried apple slices were absolutely delicious after 17 years in storage.
They were as good as the day they were preserved, and I rehydrated them and made an apple pie that fooled my husband. He honestly thought I’d made it with fresh apples, and it would have been hard to pick out the freeze-dried version in a blind taste test.
Where to Buy Freeze Dried Food?
If you’re curious and you’ve never tried freeze-dried food before, I’d suggest trying freeze-dried food before you try your hand at making your own. You can sometimes find freeze-dried food in the grocery store near the dehydrated fruit; at least, that’s where it’s kept in our local stores. I’ve actually found the quality to be really variable with commercially freeze-dried food, which makes sense…it’s only as good as the food that goes in.
Freeze-dry fruit that’s underripe or flavorless, and that’s the way it’ll come out. The best freeze-dried food I’ve had comes from Valley Food Storage, and I actually did a blind taste test with my kids. They could pick out the Valley Food storage freeze-dried fruit every time.
If you’re curious, I did a comprehensive review of the best emergency food companies on the market in 2021, after the kerfuffle of 2020 really changed the market. Just about all of them produce freeze-dried food for convenience, flavor, and long shelf life. Though the freeze-drying process is the same, some of the foods are much better than others.
Whether you’re freeze drying at home or purchasing ready-made freeze-dried food, quality matters. The result is only as good as the quality of the food that goes into the freeze-drying machine.
Traditional Freeze Drying Methods
The oldest documented use of freeze-drying for food preservation comes from South America, namely the Peruvian Andes. Potatoes are harvested in the late autumn, as temperatures in the high mountains are dipping below freezing.
Left out overnight, the potatoes freeze, and then during the day, they dry in the intense high-altitude sun. They use a freeze-thaw cycle that’s a bit like the freeze-thaw cycle we see here in Vermont during the maple sugaring season, with freezing temperatures overnight followed by sunny warm days.
After 3 days of freezing overnight and then thawing during the day, the local women “dance” barefoot on the potatoes. This helps strip off the potato peels and press out moisture. The freeze/thaw cycle continues for another 7 days, and the potatoes are walked/danced on each day in the sunlight and naturally re-frozen at night.
From start to finish, the process takes around 10 days. The finished product is known as Chuño, and it’ll store for decades without further preservation. (Just like modern machine processed freeze-dried food.)
A woman in the Andes making Chuño. She’s walking with her bare feet on potatoes that were frozen the night before, encouraging them to expel water to speed the freeze-drying process.
I missed the right weather in the fall, so I decided to try this method during our spring freeze-thaw cycle in March.
The potatoes froze overnight and then thawed during the daylight hours. I gave them a quick (and gentle) barefooted dance each day, and I even placed a box fan on an extension cord nearby to encourage good airflow. Sadly, no luck. There won’t be any Vermont-made Chuño anytime soon.
Doing a bit more research, I learned that a particular variety of Peruvian potato is used, so that may be a factor. But I also found that they do this with other roots and tubers, namely a variety of edible Lilly tuber native to their region. That implies that it could work with other types of starchy vegetables.
Beyond that, they have low pressures at high elevation that may also help to freeze-dry the tubers, working as a vacuum chamber in a way. This is traditionally done at altitudes around 15,000 feet on the Andean Altiplano. Temperature cycles are also more intense there than they are here.
During the potato freeze-drying season, “the diurnal cycle of temperature is very wide, with maximum temperatures in the order of 12 to 24 °C (54 to 75 °F) and the minimum in the order of −20 to 10 °C (−4 to 50 °F).”
This may be a case where specific environmental conditions allow for freeze-drying, but that’s not to say it can’t occur in other places. As I already mentioned, it does occur naturally in the arctic. They use a similar process in Norway to preserve fish en-mass by slow drying it in the winter months as well.
I honestly think this process warrants more testing, especially if you happen to live at a high altitude with a good freeze-dry cycle in the autumn months and dependable gentle winds.
Fish drying on racks in the snow in Norway
Freeze Drying Food in a Home Freezer
So, in theory, you can freeze dry food in your home freezer. This can happen on its own occasionally when food isn’t properly sealed, and it’s forgotten in the freezer for a long time.
At one point in my childhood, we found a pint of ice cream shoved to the back of the freezer, and the lid had slipped off. It’d been there for god knows how long, and without a lid, it’d slowly freeze-dried into astronaut ice cream all on its own.
It does happen…but it takes forever. Many months, and in that time, the food picks up flavors from the freezer and gets freezer burn at the same time. It’s kinda nasty…
Some places on the internet will tell you that you can freeze dry food on a tray in the freezer in as little as a week, but it’s just not true.
A tray of carrots was forgotten in our freezer for about a month. They’re not starting to freeze dry, though they do have some small hints of freezer burn…
We freeze a lot of vegetables here at home, and sometimes when I’m flash freezing them on a tray (so they don’t stick together), I forget them in the freezer. A week, two weeks, sometimes a month goes by before I remember to get them into a bag. They’re the same as they were when they went in and definitely not freeze-dried.
I forgot a tray in one of our freezers for 3 months one time, and while the food was a bit freezer burned, it wasn’t anywhere near freeze-dried.
Don’t believe me? Watch this experiment where a woman tries to freeze dry strawberries in the freezer by leaving them in there uncovered for 3 weeks:
It’s possible that if you had a fan or some kind of dehydrator in the freezer that it’d work eventually, but it’s in no way an efficient process. You’re going to be running that freezer for weeks or months before you get a tray or two of freeze-dried food without a freeze-drying machine.
I’ve seen other people suggest freezing the food, then placing it in a closed container in the freezer with desiccating silica gel. While that has a better chance of working, it’s not exactly a practical solution for preserving food by freeze-drying.
(And quite frankly, might not be food-safe?)
Freeze Drying Food with Dry Ice
So now maybe you’re thinking, what about freeze-drying food with dry ice?
Dry ice is frozen CO2, and it’s very cold. It’s available at party stores and big-box retailers and usually sells for about $1 per pound.
There are instructions on the internet for freeze-drying with dry ice, and all say the same thing…but none of them have actually tried it.
- Start by placing the food in a plastic bag, so it’s not in direct contact with the dry ice, but leave the bag open so moisture can escape.
- Place the bag in a styrofoam cooler outdoors and drill holes in the cooler lid so moisture and CO2 can escape. (Don’t do this indoors, you can suffocate from the CO2 filling up an unventilated room.)
- After 24 hours, the food should be freeze-dried.
Does it work? No.
First off, it takes about 24 to 36 hours to freeze dry food with a home-built freeze dryer using a vacuum pump (that method’s discussed next). It’s a much more efficient process, using electricity and much colder temps. There’s no way a cooler is going to accomplish the same thing faster.
I tried it, and no, it doesn’t work.
Reading through forums online, it looks like quite a few people have also tried it, and while the food froze as expected, it didn’t dry at all. Some things, like apple slices, are actually carbonated from being store in a high CO2 environment. That makes sense, you can actually carbonate grapes by storing them in a bottle with dry ice, and some home brewers use CO2 to quick carbonate beer without a kegging setup.
Beyond that, dry ice evaporates quickly, and you’d need many, many pounds to keep it slowly evaporating for 24 hours. That implies a huge cooler and not a whole lot of food inside. It also means at least $20 to $30 in dry ice to freeze dry a handful of food. Not exactly practical.
Cooler Filled with Dry Ice
How to Build a Freeze Dryer
Actually building a home freeze dryer is honestly easier than you think, provided you’re incredibly handy with tools. The problem is, it’s expensive to operate (lots of dry ice), and the drying chamber is comically small.
It’s good for scientific applications where you’re freeze-drying a small amount of something for an experiment, but 24 hours of work and a cartload of dry ice is hardly worth it for a cup of freeze-dried strawberries.
If you’re curious how it works, this video explains the process in detail using readily available parts that you can purchase online for about $300.
There are actually a number of homemade freeze dryer tutorials online, and all work on a similar principle.
- Small Vacuum Chamber Method – This method’s simpler to set up but has an even smaller batch size.
- Pressure Canner Vacuum Chambers – Using pressure canner bodies as vacuum chambers gets you a bit more space, but they’re around $400 each, plus a vacuum pump. This system is well over $1000 to build unless you can find second-hand pressure canners for less (which is hard to do).
- DIY Large Volume Freeze Dryer – This one, I’ll admit, is pretty intense and has a large capacity. With a welder, condenser, and a lot of stainless steel, you could build something like this that’d get the job done. It’s an impressive feat of DIY, but you’ll need a lot of tools, equipment, and know-how to get the job done. The total cost is at least $2,000 with metal and machinery, plus a few thousand dollars in tools if you don’t already have a fully equipped welding shop.
They create a cold chamber for condensing liquid, then place the frozen food in another chamber. Connect the two with a vacuum pump and keep everything cold with dry ice for 24 to 36 hours.
This method uses a good bit of electricity since the vacuum pump is running for many hours. It also requires a lot of dry ice and manual tending to keep everything cold the whole time.
The per batch cost is probably around $1 to $2 for electricity and $10 to $20 for dry ice. The problem is, batch sides are incredibly small in all of these home-built systems. Even the biggest ones can only freeze-dry a cup or two of food. (Unless you’re investing several thousand dollars to weld up a huge stainless chamber, as they do in the last video I linked to.)
Since they cost anywhere from $300 to $2000 to build, it’s not actually a cost savings when you think about all the manual operation time and per batch costs. Definitely a cool party trick though, and a great way to teach science to homeschoolers (or impress your friends).
Assuming you can do it safely, without burning anyone on dry ice or blowing the place up.
Using a Home Freeze Dryer
If you’ve read this far, you already have a pretty decent idea of how freeze-drying works. The home freeze dryers you buy actually are pretty similar to the DIY freeze dryers show in the videos above.
They’re all integrated into a single elegant unit that looks a bit like a washing machine, but it’s actually a freezing chamber with a super-efficient low temp condenser that gets the food very cold. A vacuum pump then creates low pressure in the chamber and pulls the water from the food.
To operate, you put the food in on trays and then select the cycle. It’ll have you select whether you’ve pre-frozen the food before putting it in and whether it’s a liquid (like milk or eggs) or a solid like fruit, vegetables, meat, or cheese.
The cycle will run, and sensors will determine the food’s moisture level and shut off the machine automatically when it’s finished.
Pretty sleek, right?
While home freeze dryers are incredibly efficient self-contained units, they come at a cost. Small units are just over $2000, and the largest model is around $3,500.
The inside of a freeze dryer. Food is placed on the trays, and then the chamber is sealed for the freeze-drying process.
Are Home Freeze Dryers Worth the Cost?
In theory, they pay for themselves in the first year of use, assuming you would have purchased freeze-dried food instead of making your own. For example, it costs about $75 for a #10 can of freeze-dried beef, but you can make it yourself for about $10. That includes buying the beef, electricity costs for running the freeze dryer, and vacuum bags to store the freeze-dried food.
On average, you can make your own freeze-dried food for about 20% of the cost of purchasing ready-made freeze-dried food. That assumes you’re purchasing the ingredients rather than growing them yourself. If you’re preserving homegrown produce, electricity and storage costs are about 5% of the cost of purchasing ready-made freeze-dried food.
Keep in mind that a high-quality freeze-dried one-year emergency food supply for one adult costs about $5,600. The largest capacity freeze dryer costs about $3,400, and the smaller freeze dryer models, which are better suited to one person, cost considerably less (around $2,200). In theory, you’d still have enough money to buy and freeze-dry a year’s food supply for less than you would have spent buying it.
Since the machine are built to last, you’ll get many years of use out of the machine after it pays for itself in the first year. That assumes that you use it regularly…
If you’re only planning to eat a few freeze-dried snacks a year, or you just want days, weeks, or months of long-term storage food to keep in the back closet, then it’s much more cost-effective to just buy freeze-dried food.
At my house, we grow and preserve thousands of pounds of food per year. I put it up by canning and dehydrating, but freeze-dried food is more nutritious, has a longer shelf life, and tastes a lot better. We’re actually doing some renovations to our house this year, and we’re planned in a space for a home freeze dryer.
I hope to have some detailed freeze dryer tutorials for you soon, but for now, I’m still practicing cooking with freeze-dried food using buckets from valley food storage. They’re tasty, and my kids love the novelty of cooking their own camping meals, both indoors and out.
Food Preservation Methods
Looking for more home food preservation guides?
- How to Freeze Vegetables (A to Z Guide)
- Beginners Guide to Water Bath Canning
- Beginners Guide to Pressure Canning
- Beginners Guide to Lacto-Fermentation
- Root Cellaring for Beginners (with and without an actual root cellar)
Preparedness
Preparedness goes beyond just storing food…
- How to Can Water for Long Term Preservation
- Best (and Worst) Survival Food Kits
- Best Survival Subscription Boxes
- Best Survival Seed Banks
- Survival Gardening: Our Real Life Dry Run
