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Drying, or dehydrating, foods at home can help extend the shelf-life of seasonal produce, preserve more nutrients in foods, and help provide shelf-stable foods that are easy to store. Interest in drying foods has increased with more affordable equipment options.
One method that has gained momentum is freeze drying foods at home. This method uses a specialized piece of equipement that uses a combination of vacuum pressure and heat to dry food. The first stage freezes food to -40°F which converts moisture to ice crystals. Then, under vacuum, the trays of food are heated to convert ice crystals to a steam vapor. This vapor is removed and 90 to 95% of the moisture leaves the food. This process can take hours to days depending on the food.
The cost of home freeze dryers can range from $2,400 and up depending on vendor, model, accessories, etc.
While freeze drying produces very dry food product, it does not kill bacteria. So, it is important to handle food safely to prevent contamination or cross-contamination. It is also important to read the instruction manual for the equipment to learn about specific guidelines and safe operating procedures.
Source: Let’s Preserve: Drying Foods at Home, NebGuide G2363 and Freeze-drying Food, University of Minnesota Extension