“The food preservation team spent a couple of years getting questions from the public about freeze-drying, and we recognized that there was not a lot of evidence-based information,” said Shari Gallup and Candace Heer. Gallup and Heer are assistant professors and Extension educators with the family and consumer sciences program at Ohio State University (OSU).

In response, Gallup, Heer and members of the OSU food preservation team set out to develop evidence-based resources, valuable for growers who may want to consider adding freeze-dried goods to their product lineup.

The pair shared their knowledge of freeze-drying at the 2025 Ohio Ecological Food & Farm Association’s annual conference.

How Does Freeze-Drying Work?

Freeze-drying, also known as lyophilization or cryodesiccation, relies on specialized equipment available in different sizes – home-scale to large industrial freeze dryers.

Once the food is placed on shelves in the freeze dryer, extreme cold is applied. “It’s going to work its way down to -20º, -30º or possibly get down to -50º. And it’s doing that rapidly,” said Heer.

Once frozen, the food is slightly heated creating water vapor. This shift from a solid directly into a gas is called sublimation. The air and water vapor are then removed from the freeze dryer using a vacuum pump.

After this primary drying, the food enters a secondary drying process called desorption which also uses vacuum. By applying an even lower pressure and secondary heat application, any remaining moisture is removed from the food. When these processes are complete, 99% of the water will have been removed from the food, creating a shelf-stable product.

Most foods can be freeze-dried including dairy and meat, but not foods that are high in both fat and sugar. Baked goods also don’t lend themselves to freeze-drying.

Freeze-dried food should be stored in moisture-proof, hermetically-sealed containers such as Mylar bags, PETE resealable pouches, vacuum-sealed moisture barrier bags or vacuum-sealed Mason-style jars.

For long term storage, oxygen absorbers – materials that remove oxygen – should be placed in the food storage containers. Oxygen absorbers extend shelf life by preventing color change and reducing the growth of microorganisms. Oxygen absorbers do, however, have a shelf life of about six months.

What Are the Benefits of Freeze-Drying?

Some of the benefits of freeze-dried foods are that they are shelf-stable, light and portable. Commercially prepared freeze-dried foods can have a shelf life of up to 25 years. Because home-scale freeze dryers haven’t been on the market for very long, there is limited empirical evidence about the shelf life of foods freeze-dried in these smaller machines.

Freeze-drying differs from dehydrating because no heat is used in the process, allowing the foods’ cell walls to stay intact, which preserves their vitamin and mineral content.

Not only are freeze-dried foods shelf-stable, but they retain their color and flavor. “The flavor and color when freeze-drying is still intense. The flavor and color are amazing,” Heer said.

Freeze-dried foods also lend themselves well to being rehydrated. A rehydrated freeze-dried peach, for example, will retain its shape, color and taste much more so than a dehydrated one.

What Are the Downsides of Freeze-Drying?

Since there is no heat treatment used in the process, freeze-drying doesn’t kill illness-causing microorganisms such as bacteria and viruses. If microorganisms were present in the food prior to free-drying, they can be preserved and start growing again if moisture is added back to the food.

Freeze dryers require a significant upfront investment. The largest home-scale model, which can hold 65 – 90 lbs. of product, currently costs about $14,000. This freeze dryer uses a 220-volt single phase outlet and requires a dedicated 30-amp circuit. Large commercial freeze dryers necessitate three-phase power.

Once set up, there are electricity costs to consider as well as maintenance costs.

How Can Farmers Benefit From This Technology?

Freeze-dried foods have achieved mainstream status, with freeze-dried products found in major grocery store chains.

Given this widespread consumer adoption, farmers with excess produce or high-quality seconds could consider adding freeze-dried value-added products.

Farms that have faced a natural disaster or experienced droughts might be able to capture some value from damaged crops that would otherwise be wasted.

Back Yard Farms in southern New Mexico, for example, has found success with freeze-drying produce including chilies, tomatoes, cucumbers, garlic, onions and apples. Back Yard Farms also works with other growers to preserve their excess fresh produce. This service helps other growers capture additional value from their crops but also helps to reduce food waste.

The farm started with a home-scale freeze dryer but received a $75,000 Value-Added Producer Grant (VAPG) from USDA Rural Development to purchase commercial grade freeze dryers.

Farmers could also consider creating value-added products such as backpacker meals, freeze-dried products that are geared toward toddlers and children and convenience foods such as prepared meals and soups. In the early 2000s in a Sustainable Agriculture Research & Education (SARE) project, Missouri shiitake mushroom growers explored the viability of creating a freeze-dried mushroom soup.

For livestock farmers, freeze-dried pet foods or treats, which can include organs, trim, bones and fat, may be an opportunity to add value. Freeze-dried pet foods and treats often include produce, so there is room for collaboration between farms raising different products.

Farms who do not want to make the investment in freeze-drying equipment may be able to find a custom freeze-drying business whom they can partner with. For example, in Maine, Green Gean’s offers custom freeze-drying.