What is Vacuum Drying?

Mary McMahon
Mary McMahon

Vacuum drying is a process in which materials are dried in a reduced pressure environment, which lowers the heat needed for rapid drying. It does not take place in a true vacuum, despite the name. Devices used for this process are known as vacuum driers, and can vary in size from small units designed to fit on kitchen counters to massive rooms which are used to handle things like timber products.

Vacuum drying equipment eliminates the need for workers to wear protective garments.
Vacuum drying equipment eliminates the need for workers to wear protective garments.

Drying involves reducing the moisture in an object, and is done in environments where the air is drier than the object being dried, which encourages moisture to evaporate out. This is often accomplished with heat to reduce the humidity of the air, but in a vacuum drier, the temperature does not need to be as high, and the drying is often faster. It's also possible to achieve a very high level of dryness, which may be desirable in some cases.

One advantage to vacuum drying is that it conserves energy. Less energy is needed for drying, cutting down on the economic and environmental costs associated with drying a product for storage, sale, or other purposes. This process also tends to work faster than other drying methods, cutting down on processing time, which can be important in some facilities where products are being moved through quickly.

Another advantage of drying materials in this way is a less damaging drying process. Some materials can experience problems at high temperatures, such as developing hard, leathery crusts from heat exposure during the drying process. Vacuum drying tends to retain the integrity of the original item without damaging it with heat. For foods, this can be valuable, as other drying processes can degrade quality and make the food less appealing.

Using vacuum drying equipment also reduces risks to workers. With other types of drying equipment, there are vented fumes and particles which can make people sick or which force people to wear protective garments. With a vacuum dryer, ventilation does not occur, and workers around the drier are safer. It's also possible to recover the precipitated moisture collected during the drying for further use or study.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


If you are packing clothes for a trip, and don't have much space, using a type of vacuum drying can be a life saver. By taking all the air out of the space where you store your clothes, you can fit so much more in the bag.

There are several inexpensive kits you can buy that come with the bags and the vacuum for doing this. Whenever we take a trip on our motorcycle and don't have much room for clothes, I always use this method.


We process some of our own meat, and use vacuum drying is much of our packaging. One of the advantages to vacuum freeze drying is the meat stays fresher much longer when placed in the freezer.

Just because the meat is frozen does not mean it doesn't loose its freshness over time. Using the vacuum freeze drying allows you to keep in it your freezer longer without getting freezer burn.


I know there are several advantages to vacuum drying food, and doing that with fruit is one way. When fruit is dried with a vacuum method instead of traditional drying, there is almost no moisture. This gives the dried fruit a different texture, making it very crisp and light.

Fruit that has been dried this way also has a long shelf life and is great if you like dried fruit by itself or in any kind of snack mix for backpacking or car trips. A lot of dried fruit also contains added sugar, but by using this method, you can avoid that and still have great taste.

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