How Does Freeze-Drying Work?

We’re all familiar with the term “freeze-drying” when it comes to food. It’s the best way to preserve food for the long haul. 

But many of us probably don’t know exactly what goes into the freeze-drying process. Or why it’s effective when it comes to making sure our survival food will be good 25 years from now.

Today I’d like to discuss this subject. Knowing how the process works will give you more confidence in your survival food’s quality. Both now and when you may need it in the future.

But first, I’m going to give you a little history on this subject. The machines we use now to freeze-dry food are new and complex. But the process of freeze-drying food is actually quite old and simple.

Learning the hard way

Well before refrigeration was discovered, people became aware that food spoils over time. The first few lessons in this principle were probably unpleasant ones.

But through trial and error, folks figured it out. They learned which foods went bad quickest due to bacterial growth. And which ones had a longer natural shelf life.

So, they were able to determine how soon they should eat certain foods. And which ones needed to be discarded before making them sick.

They discovered the key to making food last longer is water removal and freezing. They were on to something. 

Incas pave the way

The ancient Peruvian Incas of the Andes were the first to utilize the freeze-dried process, as far as we know.

They stored potatoes and other crops on mountain peaks. The temperatures would freeze the food. Low air pressure in high altitudes slowly vaporized water inside the food. 

Romans and other Middle Eastern populations dried fruits and vegetables in “still houses.” They used fire to dry out and smoke foods.

Much more recently, freeze-drying was effectively used during World War II. It was a way to preserve blood plasma, medicine, and eventually food for the troops. 

What about today?

These days, food is quickly frozen to start the freeze-drying process. Then the ice is turned into water vapor and removed by placing the frozen food in a vacuum.

This process is called sublimation. It involves a frozen liquid transforming directly to a gaseous state. Without passing back through a liquid phase.

People often ask if freeze-drying and dehydration are the same? The short answer is no. Actually, the long answer is also no. So, we’ll look at a medium-length answer here. 

Dehydrating food and freeze-dried food have one thing in common. They both involve removing moisture. This is essential for making food last longer without spoiling. 

Dehydration is nature’s way

Dehydration is the oldest method of preserving food. It even occurs in nature. Such as when the sun dries grain in a field or the leaves of herbs.

Dehydrating your own food can be a way to preserve that bumper crop fruit or vegetable from your garden. It can mean the difference between enjoying farmer’s market or produce aisle purchases and throwing away money.

Dehydrated foods take up much less space than cans or jars. They can be stored in flexible plastic bags to make the most of available storage room.

Bacteria, yeast, and mold need moisture to spoil food. But proper drying prevents bacteria and mold growth. And it leaves most of the vitamins and minerals intact.

The drying temperature is set high enough to remove most water. But not high enough to cook the food.

Freeze-drying is superior

The most common ways to dry food include an electric food dehydrator. As well as a conventional oven, toaster oven, or in the sun.

All methods share this: creating the proper combination of warm temperatures, low humidity, and air current. What varies is the correct handling of the type of food to be dried.

Freeze-drying food is a superior way to preserve it. Dehydrating food removes about 90 to 95% of the moisture content. But freeze-drying removes about 98 to 99%.

Some dehydrated foods can last 15-20 years. Freeze-dried food has a longer shelf life – 25 to 30 years.

Lighter, softer, & easier to prepare

Dehydrating involves heating food to temperatures that can impair nutritional value. That’s because sometimes it breaks down vitamin and mineral content. Taste and texture can also be affected. Dehydrated food often ends up looking withery or hard and crunchy. 

Freeze-dried food is usually much lighter and easier to transport than dehydrated food. Due mainly to the increased moisture extraction. Freeze-dried food can also be prepared quicker than dehydrated food. The former requires only water, while the latter can involve cooking.

How does a dehydrated product differ from a freeze-dried product? Let’s take banana slices as an example. Dehydrated banana slices, such as what you’d find in trail mix, are dense, crunchy, and probably brown. 

A freeze-dried banana slice feels airy as you bite into it. Kind of like a marshmallow in cereal. It’s white, sweet, and flavorful. The freeze-dried banana slice will be more nutritious than its dehydrated counterpart. It will stay good for much longer.   

Real food with quality intact 

More people these days are concerned about their food’s nutritional quality. Freeze-dried food provides that quality. The food is free of synthetic, artificial, and highly processed materials. 

Freeze-dried fruits and vegetables, for example, are real fruits and vegetables. Not substitutes for what nature offers. And the same is true with other freeze-dried foods. 

Freeze-dried food ingredients are virtually identical to the raw material. Which means the same flavor. 

A moment ago we mentioned that the original shape of freeze-dried food is maintained. However, if you prefer a different size or shape, that’s easily arranged. Just cut up the food how you want it prior to the freeze-drying process. 

Portable & shelf-stable 

In addition to its superior portability, freeze-dried food does not need refrigeration. It can remain shelf stable for many years. And then be rehydrated with cold or hot water quickly and easily.

It can be kept in airtight containers and accessed whenever needed. Just about any type of food or ingredient – solid or liquid – can be freeze-dried. 

Here’s one final advantage of freeze-drying food. Staying good longer means less gets tossed in the garbage. Estimates are as high as 40% when it comes to the amount of food people buy that gets wasted. 

This occurs when too much food is purchased in the first place. Or when it’s forgotten about in the back of the refrigerator until cleaning day. Or it’s mistakenly left out overnight and spoils.

Make sure to store it properly

The freeze-drying process gives food a longer shelf life. Which makes food products more versatile, accessible, and convenient. 

The original shape, color, texture, and flavor of the food product is maintained. And so are its nutrients. That’s due to keeping the cell structure of the food intact during the process.

Of course, even freeze-dried food needs proper packaging and storage. That will help it maintain taste and nutritional quality.

This means avoiding the five main enemies of food. They are air, humidity, heat, light, and pests. Keep your freeze-dried survival food in a cool, dark, and secure place. That will ensure it will stay good for as long as you need it to.


  • madonna ventling - October 30, 2023

    Thanks for the interesting information.

Leave a comment

*Required Fields