There are two basic designs of home food dehydrators on the market, without considering various DIY or solar powered designs. The first (and most economic) design involves a tower of stacked trays, with warm air forced up and out through a central column. Trays are usually circular and shaped like a doughnut, with a central hole. Settings are usually limited to on or off, which is really all you need for most applications. Because the trays don't heat quite evenly, you'll need to rotate the trays from top to bottom at least once during the drying process.
If you're planning to dry fruit, tomatoes, peppers, and other produce, the circular tower type of dehydrator will work fine. The trays are usually top rack dishwasher safe and will hold a good amount, especially if you get a model with 6 trays. I have an American Harvest circular dehydrator that I used for years to dry apples and tomatoes. I also picked up a really cheap no-name dehydrator but was frustrated when it took four times as long to do the job. Unless you luck into a good brand at a yard sale, you're likely to get what you pay for.
To feel comfortable drying beef for jerky, however, I decided I wanted a more powerful dehydrator with a thermostatic control. Although the newer American Harvester units seem to have better capabilities, I decided I'd like some additional upgrades. That brought me to the second design, a dehydrator with square or rectangular trays, where hot air is forced from the rear of the unit across the trays. The trays dry more evenly, so you may not need to rotate them at all during the drying process (unlike my old dehydrator). With no central hole to work around, it's easy to fit a lot onto each tray. You'll especially appreciate the design of the trays if you want to make fruit leather, which I found very awkward on my old circular unit.
Excalibur brand dehydrators seem popular with Dave's Garden posters in the Canning, Freezing, and Drying Forum, and that's the brand I purchased last year. We've used it to make several batches of beef jerky, as well as for drying fruit, making fruit leather, and for craft projects such as cinnamon-applesauce ornaments. I like being able to choose appropriate temperature settings for different applications. As with my circular trays, I was able to stack these trays into the top rack of my dishwasher for cleaning. As a bonus, if I remove the trays I can use the unit for proofing yeast dough or for drying larger craft projects.
Other companies make similar units, and you can also find professional models with more space, more power, and stainless steel trays and interiors to meet commercial sanitation requirements . The professional models were beyond my budget, but if I had a large orchard or wanted to make fish jerky and be sure of getting my trays clean afterward, I might wish I could afford one.
A few additional features may be worth considering. Some dehydrators come with a built-in timer. Once you've worked with your unit, you'll be able to judge a batch's time to completion fairly closely, checking on it during the last hour or two. For me, a heavy duty household light timer works fine and saved me a few bucks over the built-in version. Special sheets for fruit leather are available and may work better for you than plastic wrap or the Glad Press ‘n Seal® I've been using. Other gadgets like apple corers and banana slicers are also popular accessories.
If you're just starting to experiment with dehydrating fruit and vegetables, an inexpensive circular dehydrator may be all you want or need. If you want to make beef jerky, or if you want the convenience of the larger square trays for making leather or drying a lot of fresh fruit and garden produce, then a rear-flow square-tray dehydrator may be worth investing in. Either way, a dehydrator is a great investment for any gardening household!
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Photos by Jill M. Nicolaus. No endorsement of particular products or brands is intended; my only connection to either American Harvester or Excalibur is as a satisfied customer.