The freezing process must be quick and the vacuum process should leave only residual moisture.The two sub-processes, freezing and vacuum drying are done correctly:.When these two steps are properly completed, the food is dry enough to allow for safe storage at room temperature. This includes removing the water vapor that was once inside of the foods. The air and water vapor (gas) are removed from the food processing chamber using a vacuum pump. Once frozen, foods are subjected to vacuum drying. The colder the freeze the more efficient the next step will be. Using sublimation, the food retains much of its original texture, flavor, and nutrition when rehydrated.įreeze drying is broken down into two simple processes: freezing and vacuum drying. Freeze drying takes advantage of the scientific principle of “sublimation,” the direct transition of a solid to a gas, by removing ice (the solid) from frozen food as water vapor (a gas). The process consists of three separate, unique, and interdependent processes freezing, primary drying (sublimation) and secondary drying (desorption)” (FDA Inspection Guides, 7/93, updated 2014). The Science Behind Freeze Drying What is freeze drying?Īccording to the FDA: “Lyophilization or freeze drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. The advertising is enthralling, the possibilities seem endless: Space-age food at the push of a button! Never waste a leftover again! Gleaming, inviting, New Age-the siren call to Americans who love their gadgets.īut is a home freeze-dryer the appliance for you? Here is some information designed to cut through the advertising hype and provide a voice of reason on the pros and cons of home freeze-dryer ownership. ![]() Buying a Home Freeze-Dryer: What to Know Before You Goįreeze-dried foods are extremely popular among backpackers and culinary masters, and now freeze-dryers are available for home use.
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