How to Make Freeze Dried Food

In commercial freeze drying, foods are flash frozen and dried in a vacuum to convert internal moisture from a solid to a gas without passing through the liquid state. This process preserves nutrients in the food and makes it hard to tell the difference between a fresh meal and a freeze-dried one that's been rehydrated. Although it's too expensive and impractical to duplicate this process in your home, you can get a similar result with your freezer and a vacuum sealer.
 

Instructions

Difficulty: Moderately Easy

Using Your Freezer to Freeze-Dry Fruits and Vegetables

Things You’ll Need:
  • Disposable roasting tins
  • Awl or ice pick
  • Cutting board
  • Sharp kitchen knife
  • Paper towels
  • Freezer
  • Vacuum sealer with roll of bags
 
Step 1
Make drying trays. Use an awl or ice pick to puncture the bottom, sides and top of disposable roasting trays. The hole spacing should be a quarter inch or less so that your tins look like a screen. This will circulate the air evenly so your produce dries out quickly. If you have cake cooling racks or metal mesh trays, you can use them as well.
Step 2
Prep your produce. Wash, peel and slice your produce, making sure to remove the pith (soft spongy center), core and any bad parts. You'll need very fine slices that have a thickness that's a quarter inch or less. Leave your citrus fruits in wedges and your berries whole but any broccoli or cauliflower clusters shouldn't be bigger than your index finger. Pat your prepped produce dry with some paper towels.
Step 3
Load your produce. Arrange the produce on your roasting trays or cooling racks so that it fills up the space without contact between the slices. Fill all the trays in the same way before putting the lids back on, but don't put different fruits and vegetables on the same tray. You can stack the roasting tins in your freezer since the holes will allow air to pass through them. Adjust your freezer's temperature to its maximum.
Step 4
Test your produce. After three weeks have passed, take a sample from each tin or rack and see if it darkens. If it does, your produce isn't dry and you should leave it in for a few more weeks. When you can remove samples from the freezer without a change in color, your produce is ready.
Step 5
Seal your produce. Get out your vacuum sealer and pull on the roll of bags until you have a section that's three inches larger than the produce you'll be sealing. Cut off this section and put an end in the sealer, then press the button to seal it. Now fill the bag with your produce and put the open end in the sealer. Press the button again to suck the air out of the bag and seal the open end.
 

Tips & Warnings

 
If you don't have a freezer, you can freeze-dry your produce by putting it in freezer bags between layers of dry ice in a small cooler. It should be frozen in 30 minutes, but you'll need to check it to make sure it's hard.
 
Touch dry ice only with insulated gloves. If you handle it with your bare hands, you'll get frostbite!

Article Written By Dan Eash

Dan Eash began writing professionally in 1989, with articles in LaHabra's "Daily Star Progress" and the "Fullerton College Magazine." Since then, he's created scripts for doctor and dentist offices and published manuals, help files and a training video. His freelance efforts also include a book. Eash has a Fullerton College Associate of Arts in music/recording production and a Nova Institute multimedia production certificate.

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