Freeze drying, also called cryodesiccation or lyophilisation, is the process of drawing water out of the food and turning it into a gas, which the most common way to make dehydrated food . Freeze drying makes ordinarily perishable food nonperishable. The most frequently seen example of freeze-dried food is astronaut ice cream, commonly sold in museums and toy stores. Water is added to dehydrated food (a.k.a survival food) to bring it back to its normal state, such as freeze-dried soup and freeze-dried coffee. If you are lucky enough to get your hands on a freeze dryer, freeze drying food can be a snap. Unfortunately, freeze-drying equipment is rare and expensive.
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Things you need
- Freeze-drying machine (or freeze dryer)
- Fresh food
- Resealable plastic bag
Freeze the food in your freezer for at least two days. The food must be frozen solid before placing it in the freeze-drying machine.
Check that the chamber of the freeze-drying machine is both completely dry and clean. Place the lid on top of the chamber.
Press the "on" button, which starts the refrigeration process. Once the temperature inside the freeze dryer reaches -4.44 degrees C centigrade, the vacuum pump will automatically turn on in most machines.
Wait until the level of the vacuum pump is below 133 x 10-3 mBar. Most machines have a light that indicates when the freeze dryer is ready for use.
Place food inside the freeze dryer. Turn off the vacuum release valve and turn the refrigerator switch off.
Place the freeze-dried food in an airtight bag for maximum freshness. If you do not have a way to make an airtight seal, press out the air in a resealable plastic bag as you are closing the food inside it.
Tips and warnings
- Great foods to preserve in the freeze dryer include ice cream, soup, pasta, and rice.
- Dehydrated food is also great for camping and outdoor excursions where the less you carry the better.
- Do not leave children unattended with a freeze-drying machine.
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