IMAGINE driving to your friendly neighborhood fast food restaurant and ordering a cottonseed burger on potato peel bread--hold the onions--and a cheese whey-fortified soft drink.

These foods are not in the realm of imagination, however. They have all been created by U.S. Department of Agriculture food technologists and engineers in an effort to make appetizing, nutritious foods from products that are often thrown away, fed to animals or ignored altogether. These "garbage foods" are, in many cases, surprisingly valuable sources of nutrients.

Take cottonseed, for example. Every pound of cotton is harvested with 1.8 pounds of cottonseed. Cottonseed can be pressed for oil, but it is not used as a flour because glands in the kernel of the seed contain a substance, called gossypol, toxic to humans. Ruminant animals like cows can handle the substance, explained R. S. Kadan of USDA's Southern Regional Research Center in New Orleans. But for humans, said Kadan, the gossypol must be deactivated by high heat, rendering the cottonseed flour brown and unappetizing.

Cottonseed flour, however, is a powerhouse of protein--50 to 60 percent, compared to regular wheat flour, which has about 12 percent protein, according to John Cherry of USDA's Eastern Regional Research Center in Philadelphia. One way scientists have attempted to overcome the toxicity problem is to breed out the gossypol. Geneticists have worked for the past 20 years on a variety of cotton without the gossypol, and it is now being commercially grown on 50,000 acres in Texas, Cherry said. This glandless seed "can be processed like any other high-quality seed," noted Cherry. "It makes a beautiful source of food."

Currently, processors are toasting the glandless seeds and selling them like peanuts, Cherry said. While not enough of the seeds are being produced for widespread cottonseed flour production, one firm in Texas is producing a "cracked cottonseed" bread. The seeds are also being used in candy. In addition, Cherry said, Japanese firms are now importing the seed.

Cherry believes there is great commercial potential for another product of his Philadelphia laboratory, a citrus juice/cottonseed beverage, which contains as much protein as milk. The cottonseed dissolves well in an acid environment, noted Cherry, "so it blends nicely with pineapple juice."

One advantage of cottonseed as a vegetable protein substitute over soy products is that it does not have the distinct bean flavor of soy, Cherry observed. He and Leah Barardi of USDA's Southern Regional Research Center have been able to "texturize" the cottonseed into a product with the chewiness and structure of cooked meat for use as a meat extender. Another plus: the process for texturizing cottonseed, said Cherry, is simpler than that used to produce soy meat extenders.

But the problem with the glandless variety of cotton, according to Kadan, is that the bugs eat it: the gossypol is there, apparently, to scare off the insects. And since so much of the world's cotton contains gossypol, Kadan has taken a different approach. He and colleagues in New Orleans have developed an "air classification" method to separate the gossypol from the cottonseed. The result is a fine white flour that "can be mixed into just about anything," he said. Noting that cotton is grown all over the world, including countries like India, Mexico and China with food shortage problems, Kadan believes there is tremendous potential for the separation process.

What do you do with 44 billion pounds of cheese whey? That's how much fluid whey, a byproduct of cheese manufacturing, was produced last year, according to Warren Clark, executive director of the Whey Products Institute in Chicago. Food technologists over the years have been successful in utilizing whey, which is composed of the milk sugar lactose, salts and a small amount of high-quality protein. But every year, as cheese production rises, there is more to contend with: 10 years ago, a mere 28 billion pounds were produced.

Before stringent environmental laws were enacted, whey was dumped in streams, causing a serious pollution problem. Today about half the cheese whey produced is used in a variety of processed foods, including baked goods, ice cream and confections. Some is used to feed pigs and to irrigate land in the West. And some is still being thrown away.

Even more of a challenge is to find uses for acid whey, a byproduct of cottage cheese production. Unlike the sweet wheys from cheddar and swiss cheese, acid whey is sour, due to the longer fermentation time needed to produce cottage cheese. Virginia Holsinger of USDA's Eastern Regional Research Center found in one study that regular soft drinks could be fortified with up to one percent acid whey protein concentrate by weight without detectable changes in flavor or appearance. Sourdough breads and other bakery products have been produced with acid whey by Eugene Guy, a colleague of Holsinger at the Philadelphia research facility.

Because cheese whey contains lactose, a sugar, it can be fermented to produce alcohol. For winemaking, Holsinger selected a yeast organism that would utilize the lactose, successfully producing whey wine. "The idea," said Holsinger, "is not only for wine production, but to produce alcohol for gasahol." A firm in California is gearing up to produce gasahol from whey, she added. Also in the fermentation category, the Whey Products Institute has sponsored studies on how to use whey in place of grain for beer manufacturing.

Other foods USDA researchers are experimenting with:

* Potato peels. Upward of 1 million tons are discarded each year, removed from potatoes processed into french fries and for use in other processed foods. Paul H. Carr, a food engineer at USDA's Red River Potato Research Laboratory in E. Grand Forks, Minn., and colleagues have found the peels are a good source of dietary fiber. In addition, the peels lack phytate, a substance in wheat bran thought to inhibit mineral absorption.

* Bermuda grass. Ten million acres of Bermuda grass, used for hay and grazing, are in production in the U.S. John J. Evans, of USDA's Richard Russell Agricultural Research Center in Athens, Ga., has extracted the proteins from the grass to produce a white powder containing 80 percent protein. The powder can be used to fortify inexpensively a variety of foods. Evans said the powder is already being produced in England and Hungary.

* Desert plants. Some desert plants produce edible, high-quality seeds. According to Arthur I. Morgan, a chemical engineer at the Western Regional Research Center in Berkeley, Cal., the plants--mesquite, channel millet and ironwood--"grow where absolutely nothing else would," surviving on virtually no water. Morgan said he and his colleagues are trying to improve the crop so it produces more seed for oil and flour. Some small farmers are already cultivating the desert plants. "It's an effort to find something useful in the western desert," said Morgan, noting the seed flours make "pretty good bread."

* Tobacco. Protein nearly 90 percent pure can be removed from tobacco leaves, researchers at the Tobacco Research Laboratory, a USDA field station in Oxford, N.C., have discovered. The protein extract is being fed to mice and rats to determine its safety, said J.J. Lam of the lab. In addition, a small company in North Carolina is planning to grow tobacco for its protein for use in animal feed, he said.