Dehydrating vs Freeze Drying Food: Shelf Life, Nutrients, Costs, Convenience Compared

Most articles about the difference between freeze-dried and dehydrated are from brands who want to sell you their freeze-dryers or freeze-dried products.

Many spout numbers about how much nutrients are retained and moisture removed, but without any info to back up these “facts.”

I dug in deep to honestly look at freeze-drying vs. dehydrating. Here’s how they compare in terms of:

• Process
• Types of foods that can be dried
• Shelf life
• Nutrition
• Quality
• Rehydrating
• Cost
• Convenience

Freeze Dried vs. Dehydrated Food Which is Best?

In terms of shelf life, freeze-drying is hands-down better than dehydrating. The process removes more moisture, so the dried foods can last years or even decades if stored properly.

You can freeze-dry more types of foods, and they usually retain their quality better than dehydrated foods. However, dehydrating is much cheaper and easier, so it is usually the better choice for people on a budget or taking the DIY approach.

Process

Freeze Drying:

Freeze drying is a reasonably new food preservation method that utilizes lyophilization: a process in which ice is turned directly into a gas. It involves freezing the food and then reducing the pressure in the chamber, which causes the ice to evaporate. You can read more about freeze-drying here.

Dehydrating:

Dehydrating is one of the oldest forms of food preservation. It is a straightforward process that uses heat to evaporate moisture from food. You can hang foods to dry or use the sun, an oven, or a dehydrator machine.

Types of Foods that Can Be Dried

You can dry many more types of food with freeze-drying than dehydrating.

For example, it is possible to freeze-dry raw or cooked eggs in a freeze-dryer. Dehydrating doesn’t work well with eggs because the proteins become too hard and chewy. The same is true with many raw vegetables.

Likewise, you can’t really dehydrate liquids like milk or yogurt because it is too messy and takes an extremely long time. With a freeze dryer, you could dehydrate all sorts of liquids to make powdered milk, powdered coffee, etc.

For more about which foods can (and can’t) be dehydrated, read:

• Expert-Level Guide to Dehydrating
• Foods that Surprisingly Can’t Be Dehydrated

Food	Freeze Drying	Dehydrating
Fruits	Yes	Yes
Raw Vegetables	Yes	Some
Cooked Vegetables	Yes	Yes
Raw meat	Yes	No
Cooked meat	Yes	Yes
Milk, yogurt	Yes	No
Eggs	Yes	No
Cooked carbs (rice, pasta, etc.)	Yes	Yes
Baked goods, pancakes	Yes	Some
Fatty foods (nuts, peanut butter, mayo, butter, etc.)	No	No
Sugary foods	Some	Yes
Smoothies, juices	Yes	No
Entire meals	Yes	Some
Sauces	Yes	Yes

Shelf Life

Freeze drying typically removes more moisture than dehydrating. Because there is less water activity, freeze-dried foods have a longer shelf life than dehydrated foods.

However, the shelf life of freeze-dried foods is usually greatly exaggerated. Freeze-dried foods typically last 6-12 months without special packaging, whereas dehydrated foods last 4-12 months.

So why do people say freeze-dried foods can last up to 25 years?

This is the shelf life of freeze-dried fruits and vegetables with special packaging. This packaging is usually a Mylar bag or sealed can with oxygen removed (either with oxygen absorber packets or nitrogen flushing).

Because the freeze-dried food is protected from moisture and oxidation, the shelf life can be 25 years (or longer).

Once you open the package, the freeze-dried food will be exposed to the air. Oxygen will start breaking down the food. Moisture from the air will get absorbed into the food, and it could get wet enough for microbes to grow.

That’s why the shelf life of freeze-dried foods in normal packaging conditions is only 6-12 months.

Read: 

• Mylar Bags for Food Storage
• How to Use Oxgen Absorbers

Dehydrated foods can also be packed with oxygen absorbers.

You can also package dehydrated foods in Mylar bags with oxygen absorbers. Packaged like this, many dehydrated fruits and vegetables can last 10 to 15 years.

The catch is that you must ensure the dehydrated foods are very dry. Many store-bought dehydrated foods aren’t dry enough to be stored this way.

You’ll have to take the DIY approach and ensure you leave the foods in the dehydrator long enough. As a general rule, for long-term storage, dehydrated foods need to be so dry that they snap when bent.

Also Read: How Long Do Dehydrated Foods Last?

Shelf Life Comparison of Freeze-Dried vs. Dehydrated

	Dehydrated Fruits/Veggies	Freeze Dried Fruits/Veggies
Conventional Packaging	4-12 months	6-12 months
Packaged with Oxygen Absorbers	10-15 years	25 years

Nutrients Retained

Both freeze-drying and dehydrating preserve fiber and minerals like calcium and iron in food. Nutrients like vitamins and antioxidants are more sensitive, and some are lost during the process.

Because dehydrating uses heat and freeze-drying does not, more nutrients are retained with freeze-drying than dehydrating.

However, the nutritional difference is not that significant in real-world conditions!

A lot of websites say “freeze-dried foods retain up to 97% of their nutrition” compared to just “40%” or “60%” with dehydration. It is unclear where they are getting these facts since no studies are mentioned.   It seems that one website quoted these numbers, and other websites just copied them.

With some digging, it isn’t difficult to get actual stats on how many nutrients are retained.

For example, this study found that freeze-drying causes a 37% drop in vitamin C levels in tropical fruit, whereas dehydrating causes 49% losses.

Another study found that freeze-drying caused a 21% drop in vitamin C levels compared to a 64% loss in dehydrated fruit.

Nutrition Will Drop in Storage Anyway

It’s worth noting that many vitamins – especially vitamin C – are susceptible to heat, light, and oxygen. Even if you store your dried foods carefully, these vitamins will break down anyway. The same applies to antioxidants, enzymes, and many other nutrients.

Long-term, the fact that “freeze-drying preserved X amount of nutrients versus Y amount with dehydrating” won’t matter.

If you care about nutrition, you should be eating fresh foods. You can grow a survival garden, learn to forage wild edibles for nutrients or stockpile vitamin supplements.

Also read: Are Dehydrated Foods Good for You?

Quality

Dehydrating causes food to shrink as it dries. It gets a leathery feel and chewy texture.

By comparison, freeze-dried foods do not shrink as they dry. They end up crunchy and crispy.

Neither is better: some people prefer snacking on chewy dehydrated apples, whereas others love crispy freeze-dried ones. However, freeze-drying is usually better than dehydrating at preserving flavor and color.

Rehydration

It is easier to rehydrate freeze-dried foods than dehydrated foods. The freeze-drying process doesn’t cause the food to shrink, and there are many air pockets within the food. These air pockets mean the freeze-dried food can easily absorb water. Some foods rehydrate into almost their original state.

By contrast, most dehydrated foods will never rehydrate back into their normal state.

Dehydration causes foods to shrink and become very dense. The density means that the dry foods won’t absorb water well. It can take hours of boiling to rehydrate fibrous foods like raw vegetables (which is why you should cook most veggies before dehydrating them).

Cost

Dehydrated foods are much cheaper than freeze-dried. Store-bought dehydrated strawberries can easily be found for $0.60 per ounce. Freeze-dried strawberries in similar packaging cost at least $3 per ounce – which is 5x more.

Even the DIY approach will cost much more. A small freeze-dryer machine costs thousands of dollars. By contrast, even high-end dehydrators usually don’t cost more than $300. You can find some models for incredibly cheap or even make a dehydrator for free.

Freeze-drying machines also use at least twice the amount of electricity per hour as dehydrator machines. There are also costs of maintaining the freeze dryer, like replacing oil.

Convenience

If you want to stockpile food for emergencies, it doesn’t get easier than buying freeze-dried foods. The best emergency food brands pack their freeze-dried foods so they last 15-25 years. There are no brands selling dehydrated food with comparable shelf lives.

But dehydrating is more convenient than freeze-drying if you want to take the DIY approach to food storage and don’t necessarily need a 25-year shelf life. Dehydrators are easier to use, take up less space, and are faster and quieter. Here is how it breaks down.

	Dehydrator	Freeze Dryer
Size of Typical Machine	19x17x13	18x22x29 inches
Noise	0-65 decibels	65 decibels
Learning Curve	Easy	Difficult
Batch Time	1-24 hours	20-40 hours
Maintenance	None	Change oil

The bottom line?

If you are stockpiling food long-term, it’s likely worth the cost of buying a freeze dryer or buying from emergency food brands. Dehydrating is the way to go if you want to preserve fruits and veggies longer.

+ Resources

https://www.researchgate.net/figure/Water-activity-and-moisture-content-of-selected-freeze-dried-products_tbl1_344896764
https://link.springer.com/article/10.1007/s10068-018-0304-6
https://link.springer.com/article/10.1007/s13197-013-1173-x
https://www.foodnavigator-usa.com/Article/2016/11/14/Freeze-drying-fruit-is-top-technique-for-retaining-nutrients-Study#:~:text=Previous%20research%20conducted%20by%20Sheffield,TAC)%20%E2%80%93%20only%208%25.
https://link.springer.com/chapter/10.1007/0-387-23413-6_18?noAccess=true
https://extension.usu.edu/preserve-the-harvest/research/buying-a-home-freeze-dryer-what-to-know-before-you-go
https://www.ift.org/news-and-publications/food-technology-magazine/issues/2018/february/columns/processing-freeze-drying-foods
https://ageconsearch.umn.edu/record/140875/files/8%20-%20Ivan_evi__%20Mitrovi__%20Brki_.pdf
https://extension.psu.edu/lets-preserve-freeze-drying