We've puffed grains for breakfast, cheese for snacks.

Now it's the sweet potato's turn.

A food scientist has turned to the lowly sweet potato and found a product that, with a little work, could answer nibblers' prayers: a snack that's both tasty and nutritious.

"Snacks are always criticized for being just empty calories," said Dr. Romeo Toledo, acting head of the University of Georgia food science and technology department. "The advantage of sweet potatoes is that they also provide micronutrients."

Toledo may have created the perfect snack food: His sweet potato puffs are crisp, curly and -- above all -- good for you. Sweet potatoes, rich in beta carotene, render generous doses of health-enriching vitamin A.

With so much going for them, it's no wonder scientists have tried before to find new uses for sweet potatoes. But Toledo's process shows more promise than many.

For instance, many researchers have tried to fry sweet potatoes as a chip. But because of the high level of sugar in sweet potatoes, the fried chips become soft and gummy -- and loaded with fat. Food scientists describe the fried product as "heavy," and taste panels haven't been kind to them.

Puffed sweet potato chips, on the other hand, are light, dry and crispy. The flavor depends on the variety of potato used: Some are pungent and heavy; others are light and not as sweet. The puffs faithfully reproduce the taste qualities of the original potatoes.

The secret to Toledo's recipe is cooking with air, not oil.

"Making a food crispy without oil is tricky," he said. "There are already enough fried products on the market, so we looked for a different way to puff this food."

He starts by making a paste that's half sweet potatoes and half added starch. He dries the paste into large, thin sheets and cuts it into small pieces. These sweet potato "chips" are then suspended for perhaps 15 seconds in a stream of high-velocity air heated to about 400 F. Using an adaptation of high-temperature, fluidized-bed technology he produces a roasted, puffed product.

"A unique, pulsed fluidized bed system, as we call it, exposes all sides of the chips to uniform heat," Toledo said. "It's not really baking, since the temperatures are more in the broiling category."

In addition to yielding a crisp, curly potato puff, there's another benefit to Toledo's process.

"The dried sheets are also extremely stable," he said. "They can be cut and puffed after a storage of as much as three years."

In his laboratory at the food science building Toledo has "puffed" other foods, too, including carrots and mixed-vegetable chips.

But sweet potatoes now appear the most likely to please the palates of consumers. Toledo said food manufacturers also could spice the puffs with cinnamon or other flavorings.

Having refined the technology, Toledo is now working on the taste. The next step in his research is to put the product before a professionally trained taste panel. Once they have decided just which recipes make the best sweet potato puffs, the idea will be ready for consumer tests.

For more information go to http://www.uga.edu/~fst/faculty/toledo/index.htm or e-mail cmsromeo@arches.uga.edu