Caging Fats in Fiber

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Fat-soluble nutrients such as vitamin A could also end up trapped inside the coated droplet, rendering them unavailable to the body.

McClements maintains that it may be possible to manipulate the properties of the fiber coating to make it impermeable to lipase, the enzyme that breaks down fat, but permeable to flavor molecules, which tend to be much smaller. "You're almost using the dietary fiber as a molecular sieve, where the small molecules can get through, but the bigger molecules can't go across," says McClements.

Carefully manipulating the fiber coating could lead to other applications for the technology as well. A coating that stayed intact through the stomach but was broken down in the intestines would allow fat-soluble compounds to be targeted directly to the lower digestive tract. This approach, known as microencapsulation, has been an ongoing subject of research for decades.

"We in the academic community have been working on it for many years, and we are not there yet," says Rosenberg. His group at UC Davis focuses on using proteins and carbohydrates, rather than dietary fiber, as miniature fat containers. "There are always new horizons to explore, and it's very nice that [McClements] is doing it," says Rosenberg. He believes that this application of the technology is much more likely to be successful than attempts to reduce the effective fat content of foods.

Drugs and vitamins that might not otherwise survive the highly acidic environment of the stomach would be ideal candidates for this approach. So would fish oil, which is rich in healthful omega fatty acids but has an unpleasant taste. Unlike low-fat foods created with the goal of preserving taste, locking away the flavor of fish oil would be a good thing.

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.

"I certainly wouldn't make any claim that this is a commercial product that you could sell now," says McClements. "It's really a work in progress."