Not all fats are created equal. Scientists have known since the 1950s that replacing saturated fats with unsaturated ones can have profound health benefits. Diets that are high in solid fats, such as butter and animal fat, lead to elevated risks of cardiovascular disease and high cholesterol. But it has been difficult to phase out saturated fats—not only are they are delicious, they are also important components of a food's structure. Without saturated fat, ice creams are just sugary liquids and a hot dog has the consistency of a pet’s chew toy.
Scientists learned that lesson the hard way in 2009, when they tried replacing frankfurters' saturated fats with oils, which are healthier than solid fats. "If you try it with just oil, the frankfurters have a very tough, leathery property," says Alejandro Marangoni, who studies food and soft materials science at the University of Guelph in Canada.
In a paper published March 1 in Food and Function, Marangoni and his colleagues found a way to make oils solid but still healthy. By mixing regular canola oil with molecules of ethyl cellulose, the researchers trapped the oil within a solid scaffolding. When used in hot dogs, this gel replaced saturated fats without sacrificing texture. "It behaves as if it were solid beef fat," Marangoni says.
Of course, we've heard similar promises before. Although artificial sweeteners were marketed as a way to eat sweets without gaining weight, subsequent studies found that these indigestible sugars may make it more difficult for a consumer to control his or her body weight. Similarly, the fat substitute olestra replaced shortening in some fast foods, potato chips and other products; because olestra is indigestible, consumers could eat the greasy food without any caloric comeuppance. Unfortunately, several side effects—including vitamin malabsorption and "anal leakage"—made olestra fall far short of the hype.
The makers of the ethyl cellulose gel say they do not anticipate such problems. Canola oil is widely used in food products, and ethyl cellulose is chemically similar to the cellulose fibers we eat in fruits, vegetables and wheat bran. Similar to regular cellulose, ethyl cellulose is an indigestible chain of repeating glucose molecules; the only difference is that the hydroxyl groups of ethyl cellulose are modified into ethyl ether groups. Although ethyl cellulose is not found naturally in plants, "it would be similar to eating a small bit of paper," explains Eckhard Flöter, a food scientist from the Technical University of Berlin. Ethyl cellulose is "generally recognized as safe" according to the U.S. Food and Drug Administration, and is commonly used in pharmaceutical capsules and as a food additive in milk products and baked goods.
The researchers are not claiming to be able to turn hot dogs into a diet food. The modified frankfurters have a similar greasy feel and contain the same total grams of fat, but those fats are healthier unsaturated ones rather than the artery-clogging variety.
Although other scientists have attempted to gel oils to structurally replace saturated fats, "the beauty here is that they created a food application where the perceived properties for consumers are not significantly changed," Flöter says. Previous attempts could not replicate desired textures.
Marangoni's team discovered the gelling properties of ethyl cellulose by trial and error, and no one had expected ethyl cellulose to work so well. When fats solidify in nature, their molecules crystallize, forming spongelike structures that contain oils within the pores. In contrast, ethyl cellulose gels form spaghettilike, fibrous structures around the oil globules.