YOCUMTOWN, PA. -- The world is divided between those who like the taste of grease and those who don't. Rick Asper likes it. Sherman Buchanan doesn't.

At a McDonald's wedged between an Econo Lodge and a Maple Donuts off Interstate 83, the two patrons are on opposite poles when it comes to the chain's new Lean Deluxe hamburger.

Sherman Buchanan likes it. Rick Asper doesn't.

Hailed as a breakthrough that could reduce Americans' consumption of fat and reverse public attitudes about red meat, the Lean Deluxe was rolled out last month at 54 McDonald's restaurants here in the Harrisburg area.

Even fast food's harshest critics applauded McDonald's new product. Phil Sokolof, the Omaha businessman who took out full-page ads in newspapers denouncing McDonald's for "poisoning America," called the Lean Deluxe "revolutionary."

J associate nutritionist for the consumer group, Center for Science in the Public Interest, said it was "great news."

The leaner ground beef was developed by Auburn University in a project partially funded by the beef industry. One of the objectives set by the beef industry was that the technology be transferred to the marketplace, unlike much university research published in scientific journals only to sit on library shelves, according to Dale Huffman, a professor of meat science at Auburn and co-developer of the process.

The resulting Lean Deluxe is between 7.5 percent and 9 percent fat by weight, compared with between 19.5 percent and 22.5 percent fat by weight for any of McDonald's other patties. The whole sandwich with lettuce, tomato, pickles, onion, ketchup, mustard and bun contains 310 calories and 10 grams of fat. That's half the fat of a regular Quarter Pounder, and only about one-sixth of the fat recommended for a daily diet of 2,000 calories. Still, cautioned Hurley, it won't be a tremendous savings if you also order french fries and apple pie.

Ground beef that approximates the fat content of the Lean Deluxe patty is already available at supermarkets, according to Tom McDermott of the National Livestock and Meat Board. But the leaner the hamburger meat, generally the drier it becomes after cooking. What's different about the Lean Deluxe is its promise to taste as juicy and flavorful as ground beef with more fat.

And the trick is this: The fat has been replaced with water (9 percent by weight) and a small amount (.5 percent) of carragenan. Used in food products such as hams and low-fat frozen desserts, carragenan is a powdery white vegetable gum derived from seaweed. It binds to water and helps retain moisture. So instead of draining from the meat when it is cooked, the water stays mostly intact, presumably keeping the burger juicy.

Here in Middle America, however, Asper and his friend Michael Graham don't want water. They want fat.

The two run the area's food service division for 7-Up, sampling soft drinks all day, checking to make sure they are carbonated properly. When asked if they will participate in a taste test, Asper and Graham are finishing their lunches -- and drinking Cokes.

Wearing kelly green 7-Up uniforms (no, they don't work for 7-Up, jokes Asper, "we just like the green pants."), they are faced with two seemingly identical burgers. One is a McD.L.T. (without the cheese and mayonnaise), the other a Lean Deluxe. After a few bites of each, both men properly identify which is which, and both prefer the McD.L.T.

"It tasted greasier. Fat adds taste," says Graham. Giving new meaning to the term "balanced diet," Graham adds that he would order the Lean Deluxe again if he balanced it out with something high in fat, like an order of fries. (This is also a man who stopped buying the chain's milkshakes when they went low fat.)

Asper and Graham's reactions are just the opposite of Sherman Buchanan's, a former social worker who has drifted into McDonald's for a soft drink and a smoke. When presented with the taste test, Buchanan picks out the Lean Deluxe almost immediately. Compared to the McD.L.T., "it had a lighter, less greasy taste," says Buchanan, a beefy man with an earlobe full of earrings. He likes it better.

While the three men's reactions show that fat is in the eye of the beholder, there have been plenty of people who haven't found the difference "overpowering," according to Pat Butala, the restaurant's first assistant. The difference is not as marked as "if you're a Coke drinker and someone gives you a Diet Coke," she say.

This may be particularly true if the burgers are not tasted side by side. Take Donald and Phyllis Miner of Etters, Pa., a retired couple who have come in for lunch and who both order the Lean Deluxe. "I didn't see a whole lot of difference," says Phyllis Miner, who usually orders a Quarter Pounder.

With the new product, McDonald's is trying to offer an option for people who ordinarily order something else, as well as grabbing new customers.

Rick Ruoss, a truck driver with a bright orange oval "Rick" on his jacket pocket, says he eats at McDonald's frequently, eating about five Quarter Pounders With Cheese or Big Macs a week for lunch. "What makes it worse is when I go home and there's hamburgers for dinner," he says.

Ruoss, who tried the Lean Deluxe for the first time on this particular day, says he would surely buy it again. "It's not as greasy. It doesn't have all that mayonnaise slobbering out of it," he says.

Customer Arthur Sterner, who works in the fuel systems department at the Caterpillar Co. in York, Pa., has high cholesterol and said he doesn't eat much at McDonald's because they "don't have a selection I prefer," which he says would be chicken, fish and salad bars. But with the new burger that he has just finished eating, Sterner says he might be tempted to eat again at McDonald's.

That's the kind of customer McDonald's and other fast food restaurants are trying to attract. Spurred by sluggish growth, fast food chains have ironically started to compete on the basis of nutrition.

Practically all the chains now use 100 percent vegetable oil in frying their french fries, sell prepackaged salads or offer salad bars. Several feature grilled chicken sandwiches, and a few are selling or test-marketing frozen yogurt. McDonald's, which feeds 22 million people a day worldwide, this year introduced 1 percent low-fat milk, nonfat apple bran muffins, Cheerios and Wheaties and replaced the cheese on its salads with shredded carrots. It is also test-marketing carrot and celery sticks, reduced-oil condiments, pasta dishes and margarine instead of butter for spreading on pancakes and biscuits.

Kentucky Fried Chicken recently rolled out a new chicken product called Lite 'n Crispy in limited markets, including Washington. The chicken is still fried and thus still relatively high in fat, but the skin has been removed, resulting in an estimated 45 percent reduction in fat and 39 percent fewer calories than the chain's Extra Tasty Crispy chicken, according to company spokesman Gregg Reynolds. The differences are not that great compared to the Colonel's Original Recipe chicken, which has fewer calories and less fat than the Extra Tasty Crispy. The chain is not going to make any health claims about the new product, which comes with a garden salad and multi-grain roll, he added.

In the next few years, consumers "will be seeing a new KFC," Reynolds said. The restaurants will look brighter, the menu will be expanded and there will be more options to fit "the active lifestyle," he said.

Although McDonald's was the first fast-food company to test a water-and-carragenan-containing burger, others have known about Auburn's nonproprietary beef research, and "there's virtually nobody who's a big player in the ground beef business who's not interested in it," according to McDermott of the meat board.

Huffman said that since the announcement of the Lean Deluxe, he has received more than 200 inquiries from all over the world -- from major food processors, supermarket chains, food analysts, meat packers and even Walt Disney Enterprises. They all want to learn about the technology, he said. (In very basic terms, it involves taking a coarsely ground cut of lean beef, usually round, then adding the carragenan, water, a flavor enhancer (not monosodium glutamate) and a little salt, and grinding it again, Huffman explained.)

John Merritt, senior vice president of public relations for Hardee's, said that the chain had the Auburn technology in house when it rolled out the Lean 1 in June. It decided to test market the Lean 1 as an 18-percent-fat burger with 100-percent ground beef instead. Nevertheless, Hardee's is conducting market research between its in-house carragenan-containing burger, the Lean Deluxe, the Lean 1 and another lower fat patty and may roll out a reformulated lean burger.

2 McDonald's "has changed the ante in the game," Merritt said, adding that Hardee's is following consumer reaction to the Lean Deluxe with great interest. Hardee's wasn't quite ready to take a stab at selling a carragenan-containing product, Merritt said, because it wasn't quite sure what consumer reaction would be to a hamburger made with less than 100-percent beef.

Although big chain hamburgers are all made from 100-percent ground beef, a survey conducted by one fast food company showed that 45 percent of the American public thinks fast food hamburgers contain something other than 100-percent beef. A third of those thought the "other" ingredient was soy protein.

It's not just fast food companies that are anxious to find a palatable, lower-fat burger. In October, the U.S. Department of Agriculture announced that it was seeking bids for a burger for the school lunch program with a maximum of 10 percent fat. The current maximum is 24 percent for all-beef patties, and 22 percent for soy protein-added ones.

Barbara Cope, chief of USDA's commodity procurement branch, which solicited the bid, said that the agency has received a variety of burger proposals, including those that include carragenan, like the Lean Deluxe, as well as 100-percent beef burgers and beef and soy combinations. USDA is currently conducting sensory evaluations (high-tech taste tests) of the products at its Beltsville research center, Cope said.

And Auburn's Huffman said he is working with several supermarket chains that would like to introduce the new lean ground beef in their stores.

Right now, however, the cashiers at the McDonald's in this town halfway between York and Harrisburg are busy promoting the new burger. "Welcome to McDonald's. Would you like to try our new Lean Deluxe?" Carol Remaly asks a man in a blue cap and a Chem-Dry Carpet Cleaning T-shirt. "Sure. Why not?" he answers.

In fact, to break up the boredom of the job and keep motivation up, Butala organizes employee competitions, such as awarding cash prizes to the staffer who sells the most Lean Deluxes. Christy Otlo won it last, pushing 12 of the burgers in an hour. She took home an extra $10.

Although there is no local or national advertising for the new product, there's a big banner on the outside of the restaurant, signs on tables, signs at the cash registers and the come-ons from the cashiers. So far, according to Butala, the store is selling "more than we expected to" -- about the same as when the McD.L.T. was rolled out. But that product was introduced with national advertising.

The Harrisburg area was chosen for the operational test because in fast food-ese, it's the "average QSR market," according to Frank Gihan, senior marketing manager for community development for McDonald's Philadelphia region. That means the "quick service restaurant" attracts a little of everything. As Butala put it, "you name it, we get it -- tour buses, local people, truck drivers."

The test is called "operational" because, unlike a regular test market, McDonald's isn't so much interested in how well it sells as how well it works. "Do we put the ketchup on first, last? How long does it hold up? Does it get dry after 10, 15 minutes? All that is being tested," said Gihan.

The product is cooked on the chain's clam-shell grills, which hug the burgers on both sides and automatically pop their tops when the cooking is complete. Back in the kitchen, Butala points to the freezer where the frozen soon-to-be Lean Deluxes and McD.L.T.'s rest side by side. The leaner burgers have more white spots -- ice crystals from the water, she explains.

Meanwhile, back at the plastic and oak booths, 4-year-old twins Sara and Angela Schreffler are asked which burger they like better. Sara points to the Lean Deluxe. Angela prefers the McD.L.T. "It's more good than the other," she comments. Large vocabularies and well-honed palates they don't yet have, but they do know what they like.