Fries on a diet

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Looking a french fry isn't rocket science, but it does take a bit of chemistry to tell a "good" fry from a less nutritious one. The keys are timing, temperature and taste, along with the choice of potato and oil.

The "bad" term receiving a lot of publicity these days is trans fat, short for trans fatty acids, which are synthetic fats made by adding hydrogen mainly to vegetable oils. This process, called hydrogenation, is employed by many manufacturers of packaged, processed and fried food to enhance flavor and product stability.

Along with an excess of the saturated fats found in great number in animal fats, cocoa butter, butter and some tropical fats, trans fats increase levels of bad cholesterol and decrease the good kind, with harmful effects on our well-being, especially the cardiovascular system.

Trans fats get their name from the position and behavior of atoms in the hydrogenating process, as described by Harold McGee in his classic book "On Food and Cooking: The Science and Lore of the Kitchen." A saturated fat is loaded with hydrogen atoms in a way that makes the melting point notably higher and therefore easier to handle in cooking. Shortening and stick margarine, for instance, are more stable cooking tools than vegetable oils but are famously high in saturated fat.

Since January, the Food and Drug Administration has required food manufacturers to state the amount of trans fat on product labels by way of raising awareness of the issue and encouraging the good eating habits that nutritionists and dietitians are in the business to promote.

"Trans fat has become a buzzword; consumers know the word, but not what it is," says Dawn Jackson Blatner, spokeswoman for the Chicago-based American Dietetic Association. She distinguishes a trans fat that is a naturally occurring fat found in things such as meat from one artificially created by hydrogenation.

"Cakes, pies and cookies are where Americans get trans fats," she says -- a total of 40 percent in the national diet comes from processed food. "French fries contribute 8 percent. That is why the fry is getting attacked. ... People forget that the pure definition of trans fat is stick margarine -- about 15 to 20 percent of our total consumed as a country."

The comparison should make McDonald's and other fast-food chains feel better. They have been under attack for not working hard enough to reduce trans fats and eliminate them where possible. Repeated requests to speak to a McDonald's nutritionist were answered by an e-mailed statement saying the company is continuing "to work diligently on ways to further reduce TFA levels."

The amount of fries bought and consumed nationally has declined in recent years, but people are prone to eat huge numbers of them at a single sitting in the belief that such small, skinny sticks can't possibly be as dangerous as, say, a sirloin steak. Fries remain such an American icon that the winter edition of Chefs Express, a trade magazine sold to food professionals, uses them to illustrate an article titled "Truth, Lies and Transfat Myths."

"No oil can safely be used to fry. But some are less harmful than others," the article notes, naming among them olive, coconut, palm kernel oils and butter in small quantities as well as "refined" peanut and avocado oils.

"The basic reason you want to hydrogenate vegetable oils is because they are an inexpensive form of fat. But they are prone to going stale and rancid easily, especially in a high-volume retail operation," Mr. McGee says in a telephone interview from California. "So by hydrogenating, you make them more stable -- not rancid, so they can be used longer. And the other thing is, the more solid the fat is at room temperature, the less greasy it feels on the french fry."

Manufacturers are working out ways to make hydrogenated saturated oil without creating trans fats in fries, he says, but the technique is difficult and expensive, and until recently, there has been no economic incentive to invest in the operation on a large scale.

Potatoes alone are a good source of energy and vitamin C, Mr. McGee notes in his book, with mealy types such as russets, blue and purple varieties preferable to so-called waxy types because the cells of the former have more dry starch, making them denser in texture. In cooking, the starchy cells swell and produce "a fine, dry fluffy texture." A low-temperature preheating process called blanching helps strengthen cell walls and protect the texture, he writes. It follows, too, that the smaller the chip or fry, the more surface area is exposed to oil and, hence, the more trans fatty acids are consumed.

"I don't eat fries very often, and I'm convinced you can achieve a perfect one without boiling it in poison, which is the term the public needs to think of," asserts Dr. David Katz, associate professor of public health and director of Yale University's Prevention Research Center. A specialist in the neuroscience of food, he is the author most recently of "The Flavor Point Diet," whose premise is that hidden appetite-stimulating flavors distort a healthy approach to eating.

"The issue is that oil low in saturated fatty acids such as olive, corn, sunflower seed, canola and grape seed, tend to be good for us but are bad for shelf life and the melting point," he notes. "So the food industry does partial hydrogenation, which saturates the carbons in fat, and that becomes trans fatty acids."

The McDonald's Web site gives a total 4 grams of saturated and 5 grams of trans fat in a 4-ounce portion of fries. (The company since has raised the number of trans fat grams to 8, saying that new measurement methods were used.) The words "partially hydrogenated" are repeated four times in the list of ingredients.

"Every potato is different, and people have to follow their own instincts," says Ellen Gray, manager and co-owner of Washington's Equinox restaurant along with her husband, chef Todd Gray. Whether fried or baked, the cut-up potatoes in the Grays' hands are blanched -- simmered with some salt --for three minutes at 275 degrees beforehand in either oil or water.

Expensive grape seed oil is ideal for frying the potatoes, she says, "because it doesn't carry over the fat or the oil flavor. It isn't even as fatty as vegetable oil. Olive oil doesn't fry well because it has a high smoke point and burns quickly. Animal fat, by contrast, has a low burn point."

Whether done in grape seed or peanut oil, the batch next is put on paper towels to be tested for tenderness and then refried for an additional two minutes. Sprinkle on some sea salt, and the result is a custom-made side dish: crisp on the outside, tender within.