First off, let's clear up the Sweet Potato versus Yam thing. Often here in the U.S. the two are interchangeable. Not so much when it comes to the nutrition inside each one. Unfortunately yams got the short end of the vitamin stick. They are mainly just a tasty, starch-based root crop. Sweet Potatoes, however, are rather awesome wonder foods!
The greatness of these veggies is beginning to show itself on the commercial market, but be aware that studies (National Food Administration of Sweden, 2002) have found commercial processing to be quite unhealthy. Due to the high heat of the processing, many nutrients are lost and harmful carcinogens (PAH - poly-cyclic aromatic hydrocarbon and Acrylamide) are created. Unfortunately, those commercial sweet potato chips are quite nasty for you.
Much like standard potatoes, there are some nutritional concerns with the ways they are normally dehydrated. The commercial production companies run into problems due to the high heat and frying often used. Luckily, you can avoid both of those from at-home processing, but you still need to maximize the nutrition.
Most importantly, do not boil your sweet potatoes. The water removes large amounts of Vitamin C and greatly diminishes the nutritional value of this awesome tuber. Bake them and then let them cool. By baking and then allowing the potatoes to cool, you are converting the starch into resistant starch. Resistant starch is not broken down by the small intestine, but is utilized by the large intestine. By being broken down later, the glycemic index is drastically reduced. The digestible fiber and vitamin content of the veggies can also be increased significantly if you bake them first. One medium baked sweet potato contain 438 percent of your daily needs of Vitamin A and 37 percent of your daily need of vitamin C.
There is also a very nice smattering of B2 (riboflavin), Vitamin E, iron and potassium all smushed in there. The potassium is of large importance due its ability to regulate your electrolytes, metabolism and hormones. Anytime we can sneak large amounts of potassium in when we backpack, I'm all for it.
In short, sweet potatoes are pretty great way to sneak in some of the important nutrients that come in fresh foods when fresh really aren't available. We mash our sweet potatoes and use them as a base in soups, stews, rice and burritos. You would be amazed at well the flavor blends, but ramps up the nutrients of other foods.
If you are making sweet potato chips, you would do them just as we do our standard potatoes. Click over Here, and follow this process. You may want to slice them thinner, if you are really wanting something "chip" like.
Dehydrating Mashed Sweet Potatoes
Bake your sweet potatoes just like you normally would, but turn off the oven about a half hour early. You want then fairly smurshy, but not completely cooked through. Leave the potatoes in the oven and allow the potatoes to cool. This will allow the starch to convert, while the potatoes are also finishing their cooking slowly. Once cool, the skins will bubble and the potatoes can easily be peeled.
Once peeled, mash the potatoes into a fairly smooth glop. They don't have to be blended up or look like they would be read for the dinner table. Mainly you just want a nice blend you can sort of smear.
Using a spatula smear the glop onto a fruit leather tray and dehydrate at 135 degrees for 8-10 hours. Check at 8 hours and see.
The above photo is not dry yet. You don't want any give in the sweet potatoes. Often times you will think they are done and then find pockets on the undersides which are still wet or soft. Put them on again and give them a little more time.
When truly dry, they will be brittle. You should be able to pick the entire disk up like a Frisbee or it will crack clean in the middle. If they are even remotely bendable, they aren't ready.
Break apart the brittle disk and food process till you have a fine powder. Due to the density of these veggies, if they are left in chunks their rehydration time can be quite lengthy. They also can provide a chunky feel to your food. By pulverizing them you get a smooth, hardy quality and a really nice mix between sweet and savory.
Once powdered, these will store for over a year and be perfectly wonderful to mix into darn near anything. It is another great way I get my boys (both the 38 year old and the 7 year old) to eat veggies. Muffins, rice, stew, casserole, soup, you name it and sweet potatoes work pretty well all mixed in.