As of July 1, restaurants in New York City must eliminate oils, shortenings, and margarines containing trans fats. (Dima Gavrysh/Associated Press)

Starting this week, a New York City ban on trans fats will extend to almost all prepared food in restaurants, bakeries, cafeterias, salad bars and food carts.

There will be a three-month grace period before big fines are slapped on violators. The artery-clogging substance was first banned from cooking oils last year.

Chefs who relied on trans fats to make their pie crusts flaky, their crackers crispy and their muffins moist have worked overtime finding substitute ingredients. They have burned through hundreds of gallons of oil, shortening and margarine trying to retool old recipes without damaging flavour, texture or colour.

Fast food giants from McDonald's to Taco Bell say they have banished trans fats without having to drop a single item from their menus.

Baking supply companies have introduced a host of replacements for the partially hydrogenated vegetable oils that are the biggest source of trans fats. Not even Crisco is made of Crisco anymore. The company reformulated all of its products last year to have "zero grams of trans fat per serving."

City health commissioner Thomas Frieden, who launched the anti-trans fat initiative, said it is too early to tell what percentage of the city's restaurants will fully comply by Tuesday. But he said his department had heard relatively few complaints so far from frustrated chefs.

"We think it is going extremely well," he said.

Those who reject the ban and get caught face a $2,000 US fine starting Oct. 1.

Americans have been baking with vegetable shortening loaded with trans fats since the invention of Crisco. Unlike frying oils, whose main purpose is to conduct heat, shortening is a major contributor to taste and texture.

There are plenty of substitutes, including natural fats like butter or lard, palm oil, and a growing list of new oil blends. However, for some bakers, adjusting has been painful.

Family-owned bakeries in Philadelphia raised such a ruckus that city lawmakers gave them an exemption from the trans fat ban that passed there last year.

Fast food chains alter recipes

The New York ban may have had its biggest effect on fast food chains, which have transformed recipes nationwide.

Dunkin' Donuts eliminated trans fats from its doughnuts in October, months ahead of the deadline for frying oils. The company's cooks began experimenting with a replacement oil back in 2003 and tested 28 different substitutes, sometimes with disastrous results, before picking a new blend of palm, soybean and cottonseed oil.

The company sold 50 million trial doughnuts in secret, to see how customers would react, before announcing it had made the switch. Dunkin' Donuts said customers didn't notice the change.

In fact, Laura Stanley, a consultant who has been working with smaller New York restaurants seeking to adapt, says there doesn't seem to be a food that can't be saved.

She worked with a program based at New York City College of Technology in Brooklyn that tested replacement ingredients, held classes, and came up with fixes for recipes that seemed particularly problematic.

"We were pleasantly surprised," Stanley said. "We'd anticipated a lot of problems with flavour, but for most of these items the new products performed fine."

The one disappointment is that many chefs have been turning to products high in saturated fats, like palm oil, as a replacement. Some research suggests those fats might be just as bad for you as trans fats.

But there's hope: a second generation of low-cholesterol oils is coming out now. Stanley said there have been encouraging signs that they might be improved enough to persuade chefs to use them.