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What Is Freeze Drying?

April 15, 2019 4 min read

The food storage movement has been gaining traction over the past few years. We can thank Mother Nature for this. She has shown us that emergency preparedness is critical and cannot be neglected. Water, medical supplies, and a plan of action are crucial when facing a crisis. The key to survival often comes down to the intake of nutrients (calories specifically.) This is where freeze-dried food shines. It has a long shelf-life, is incredibly delicious, and can be the make or break of any home's emergency storage.

This is all great, but the question is: How does freeze drying work?

“Freeze dried” doesn’t exactly mean: toss fruit in the freezer, dry it in the sun, then voila… little nuggets of edible treats.  Fun fact: that’s not how it works. Freeze drying (also known aslyophilization) food is actually pretty complicated. Let’s start with a little background on the subject. This process was developed during World War II as a way of preserving blood plasma. Battlefield emergencies required healthy organic plasma to be available without the requirement of refrigeration. This process allowed medics to carry medicine, such as penicillin that retained a higher “shelf life.”  The technologythen found its way into consumer food products after the end of the war. The first largely marketed product to use this technology was coffee. Almost 98% of the water content is removed during the process, which makes it nearly contamination-free and resistant to bacteria and deterioration. Dehydration makes it almost impossible for harmful bacteria to survive. Some food and liquids are more suited for the process than others, but technology today has made it possible to freeze dry all kinds of tasty morsels, such chicken, beef, crab, lobster, vegetables, coffee, and fruits. All of these can be combined with flavorful herbs and spices to create meals that are actually quite scrumptious.

What is the manufacturing process?

A processing facility (worth its weight in salt) is generally a large plant filled with modern equipment. Each area that has direct food handling must adhere to government regulatory procedures. This includes several areas of the facility that must meet strict sanitary guidelines, such as the receiving area, storage for raw foods, cooking process, freezing and drying chambers, and packaging rooms. Most facilities will include a research area where improved methods are developed, and have a test kitchen to create techniques that will provide the best quality food preparation and taste.

Testing and Preparation

  • Step one- The food is checked for purity, contamination, bacterial counts, and spoilage. A lot of this will depend on the harvest season.
  • Step two – Some foods are inedible without going through a proper cooking process. This remains true during thefreeze drying process. Food is usually purchased already cut into small pieces. Even if they are pre-cooked and frozen, they will still be cooked in large kettles to make sure they are prepared at a safe temperature. Vegetable and fruits are purchased cut, peeled, and pitted. With a thorough rinse, they are ready for the next step.


  • On flat metal trays, stacked 20-30 high, the food is spread. Trays are pre-chilled too prevent partial thawing during handling. Food is then moved to a “cold room,” where the temperature can be as low as -40°. In this extreme environment, food freezes quickly. On average, one facility will have at least a dozen cold rooms working there frosty magic on a daily basis.


  • Food is now moved into a vacuum drying chamber, which is a large cylinder with a hinged lid that starts the process known as sublimation. During this process, solid material changes to a gaseous material without turning into a liquid form.
  • During sublimation, ice crystals are trapped in the frozen food pieces, which are then forced to change into water vapor without becoming liquid. In thedrying chamber air is vacuumed out to reduce the pressure and the temperature of the food is raised by heat lamps. When the chamber is evacuated of air, the pressure is below the threshold at which water can simultaneously exist in a sold, vapor, or liquid state. This is known as the “triple point of water.”
  • During the triple point stage, ice crystals are trapped in the pieces of frozen food and morph into water vapor. This vapor is then eliminated from the chamber, leaving the food behind. The pieces of food are now filled with very small voids, just like a sponge.
  • The drying process allows for food to retain its size and shape and is now prepared to reabsorb water easily during preparation.

Sizing and Blending

Once removed from the drying chamber, food is tested for purity and moisture content. Some foods are ground into a powder or blended to meet the consumer’s ideal specifications.


Fact of life: There is Moisture in the air. In order to prevent food from absorbing that moisture, airtight containers are necessary. This is where Mylar packaging shines. All plastic breaths including food storage containers, but Mylar bags cut this air transfer down to almost nothing. If you are looking for a food storage company that is using the latest technology, find out if their packaging includes Mylar. It’s light proof, oxygen proof, air proof, andwater proof, so basically… the best of the best when it comes to food storage.

Quality Control

Re-hydration requirements vary for different types of food. Freeze drying facilities have electronic microprocessors that regulate temperatures, times, and pressure used throughout each step of the process. This is controlled by strict government guidelines and assures that the food is safe for public consumption.

The Future

When we hear freeze dried” we generally assume it is pertaining to emergency food, but that is not the only substance being preserved through this process. Pharmaceutical products, such as vaccines and antibiotics, chemicals, pigments, and ceramic powders, and aerosol sprays are also starting to trend in this fascinating world. Freeze dried food can not only be life saving in the event of an emergency, but advances in technology have also made it absolutely delicious, tasty, scrumptious, mouth watering, filling and nutritious… you get the point. Stock your shelves today!