A technique to coat droplets of fat or oil with layers of dietary fiber may prevent these substances from being digested. The technology might allow compounds that would ordinarily be destroyed in the stomach, such as certain vitamins or drugs, to be delivered intact to the lower digestive tract. Some scientists think that this encapsulation approach could also lead to tasty but nonfattening food products.

A team of food scientists at the University of Massachusetts, Amherst, has been developing the technology as a way to stabilize fats so that they hold up better during food processing procedures, such as freezing and drying.

To produce the fiber-coated fats, the researchers first create an emulsion—a solution of tiny fat or oil droplets suspended in another liquid—and stabilize it using an electrically charged surfactant that sticks to the surface of each droplet. Then fiber particles with an opposite charge are added to the mix. Electrostatic forces cause the fiber to adhere to the surfactant-coated droplets, creating a protective layer.

“We had the idea that if you did that, and the dietary fat was indigestible, then you could have these low-fat products,” says food scientist Julian McClements, who led the research. If the dietary fiber can pass through the gastrointestinal tract undigested, the fat droplet contained within it will go undigested as well, and thus not contribute to weight gain. In this way, the food’s effective fat content would be lower than its actual fat content.

The technology is still in a very early stage of development. Preliminary tests show that fiber-coated fats can evade breakdown in a test-tube model of the digestive system, but McClements hasn’t yet succeeded in creating droplets that can survive a trip through the gastrointestinal tract of a mouse. And it remains to be seen whether this approach will have the same side effects that plagued olestra.

—Jocelyn Rice, Technology Review, Published by MIT, 2/19/08