The guilt level associated with french fries and fried chicken from Eat'n Park Restaurants should drop by the end of September when the chain completes its switch to an oil that contains no trans fats, the by-product of the partially hydrogenated vegetable oils that makes foods crisp and creamy but at a cost to the heart.

The switch, which has taken more than year to study and implement with help from Penn State University researchers, puts the Homestead-based chain at the forefront of one of the food industry's hottest health issues.

By January, the government is demanding food manufacturers add a line on their labels for trans fatty acids, just below an existing one for saturated fats. Both have been associated with an increased risk of heart disease. Companies from the H.J. Heinz Co. to Kraft have been tinkering with their recipes to try to win the trans fat-free label for as many products as possible.

Though squeezing trans fats out of the nation's restaurants is likely to be more difficult, pressure is building there as well. Just last week, the New York City health department asked 20,000 restaurants and 14,000 supermarkets and food suppliers to voluntarily stop using the partially hydrogenated vegetable oils blamed for adding artery-clogging trans fats to foods.

That may not be the easiest thing to do. McDonald's a few years ago announced a plan to significantly reduce trans fat and saturated fats in its french fries but ran into problems trying to make it work. "The change has taken longer than anticipated, but we are continuing with ongoing tests," the company said in a statement.

McDonald's has reduced trans fat levels in its Chicken McNuggets and some other products and added information on the subject on its Web site. Other chains have been working on the issue, too, with Au Bon Pain earlier this year rolling out trans fat-free baked sandwiches to join its trans fat-free muffins and bagels.

Officials at the 79-restaurant Eat'n Park chain started taking a look at the issue not long after the Department of Health and Human Services announced the food labeling initiative in 2003.

Although cholesterol-raising trans fats occur naturally in some foods, the majority are created when hydrogen is added to vegetable oil to increase the shelf life and flavor stability of foods. Americans tend to consume far more saturated fats than trans fat, but both are considered unhealthy, according to the U.S. Food and Drug Administration.

The idea of making Eat'n Park's food healthier was appealing, but customers were likely to get upset if everything suddenly started tasting different, said Brooks Broadhurst, the company's vice president of purchasing.

Officials sent the soybean oil that the company has used for more than a decade to Pete Bordi, director of Penn State's Center for Food Innovation, along with eight or nine alternatives. Bordi did lots of frying in the various oils, reusing the oils for several days just as a restaurant would, to see how well they held up. About 50 volunteers provided taste-testing services.

The focus was on the fries. "If you can do it with [fries], you can do it with everything," said Bordi.

About six months ago, the researchers sent back two choices -- one a blend of different oils and the other canola oil made by food conglomerate Cargill from seeds produced by Bayer Corp. The second got Bordi's recommendation because it lasted longer and tasted better. The taste-testers even thought french fries made with canola oil tasted better than those done in the restaurant's usual oil.

Eat'n Park tested the new oil in about 10 restaurants, including the Waterfront site near its headquarters, plus some company cafeterias that it manages. "Most of our customers didn't even notice, which was the key," Broadhurst said. Company officials were happy with the canola oil because it also happened to be low in saturated fat.

Eat'n Park's traditional soybean oil has 3 grams of saturated fat and 2 grams of trans fat, while the new canola oil is trans fat-free and has 1 gram of saturated fat.

The company, which uses about 1.5 million pounds of oil a year, expects to spend more on the new product, although it has hopes of making up some of the expense because the canola oil lasts longer.Costs could be a factor for smaller restaurateurs that try to cut down on trans fats, said Joan Procopio, a registered dietician with the Allegheny County Health Department. The chemically altered vegetable oils that came into common use years ago were created because they gave products longer shelf lives and didn't catch fire easily. The array of alternatives has since grown.

The coming food labeling changes may help small operators reduce trans fats. For one, they will be able to better see and measure trans fat levels in the foods they are buying. In addition, manufacturers already are working to offer more products that can be sold as trans fat-free in the face of the anti-trans fat movement.

Pittsburgh ketchup giant Heinz was happy to learn that an assessment of its Smart Ones frozen entrees found only four of more than 80 items contained trans fats. The Ore-Ida line of potato products is presenting challenges, although several new Tater Tot products will meet requirements for a zero trans fat label.

As consumers begin to focus more on this issue, the marketing benefits of trans fat-free foods may increase. Heinz hopes it can point out the advantages of its trans fats-free baked snacks, Bagel Bites, as compared with a number of other competing snack foods.

"It's really a hot topic," said Penn State's Bordi, whose research center is working on projects for other companies, including Altoona convenience store chain Sheetz.

White Oak-based Kings Family Restaurants, with almost 40 locations, also has been talking to its oil vendors about steps it can take, said Jim Harrington, vice president of marketing and advertising.

Despite all the effort, Eat'n Park will not be able to claim its menu is trans fat-free, the goal that New York has set for its restaurants. Though the new oil will be used in the fryer and in salad dressings, baked goods such as cookies and crackers are not affected by the change.

The company's signature Smiley Cookies do contain a small amount of trans fat. Broadhurst said work is in progress to find ingredients that will maintain the flavor but get rid of that fat.