By Erinn Barcomb-Peterson
Try making a batch of biscuits or a flakey piecrust without trans fats, and you won't find too many options.
But technology being developed at Kansas State University could allow food manufacturers to create vegetable shortening and other hydrogenated oils without artery-clogging trans fatty acids.
"Our goal is to figure out the basic technology that would make this project work," said Mary Rezac, professor and head of the department of chemical engineering at K-State, pictured at left.
Supported by a $360,000 grant from the U.S. Department of Agriculture, Rezac is leading a research project with co-principal investigator Peter Pfromm, professor of chemical engineering. They want to help companies turn more healthful liquid vegetable oils into semisolid products -- like shortening or margarine -- that go into cakes, cookies and other baked goods but that don't have as many trans fatty acids.
"The USDA is interested because vegetable oil is a very ubiquitous oil," Rezac said. "Soybeans grow really well in the United States, but their oils are liquids at room temperature."
The difference between trans fats and fats that are more healthful is all in the chemistry. Liquid oils like those that come from pressing olives or soybeans have double bonds between the atoms that compose them. Rezac said that in pressed oils, these double bonds are all in the cis configuration. If you look at cis fatty acids at a molecular level, they have a curved "backbone" connecting their atoms. That curved backbone means they don't pack well if they fall out of the bloodstream, which means you'll have fewer clogged arteries.
In contrast, trans fatty acids have a single bond between their atoms and a straight "backbone." This stick-straight shape makes the molecules easy to stack on one another to form a semisolid product like shortening that has a longer shelf life than a liquid like olive oil. But this shape also means they fall out of the bloodstream and easily build on top of one another in your arteries like sticks of spaghetti, Rezac said.
Flip through your great-grandmother's cookbook, and you can see that some of the foods we make today with products like vegetable shortening were long ago made with such animal fats as lard. But about a hundred years ago, manufacturers figured out how make liquid vegetable oil into semisolid oils by adding hydrogen to break the double bonds that keep the oil liquid.
Rezac said this process involves adding hydrogen and a catalyst into a vat of the liquid oil. The problem with this hydrogenation method, she said, is that in addition to creating more sturdy forms of the cis fatty acids -- and giving us vegetable oil products like margarine and shortening -- this method also makes lots of the stick-straight trans fatty acids we don't want.
At K-State, Rezac and researchers are developing a technology that adds hydrogen to liquid oil in a different way that results in more of the desired cis fatty acids and nearly eliminates the trans fatty acids in the semisolid product. This technology is a membrane polymer -- Rezac said this is like your kitchen sponge -- through which hydrogen has to pass before it can get into the liquid oil. A thin layer of metal is added on top of the polymer to act as a catalyst and to control the way hydrogen comes through. Results are showing that this method produces fewer trans fatty acids than the conventional hydrogenation method.
Rezac and K-State researchers are working to optimize the process and get the best possible design so that food manufacturers will have the technology to make products like shortening or margarine without trans fatty acids. Rezac said tests are beginning to yield a product low in trans fatty acids that also is the desired consistency for home cooks and food manufacturers.
"With this technology, we can get the product to the place where we can make cakes and other baked goods with trans fat-free shortening," Rezac said.