Striking Oil: High-pressure processing minimizes trans fats

Improvements to the techniques used to hydrogenate vegetable oils could soon fill store shelves with packaged foods containing reduced quantities of unhealthful trans fats.

Manufacturers use the process of hydrogenation to make vegetable oils more solid at room temperature and thus suitable for use in margarines, shortenings, and commercial baked goods. However, hydrogenation creates unnatural trans fats that have unhealthy effects on cholesterol concentrations in the blood (see Stronger Proof That Trans Fats Are Bad).

Beginning next Jan. 1, food companies must label products to reveal their trans fat content (see No Hiding Most Trans Fats), and some companies have already begun doing so. The Food and Drug Administration permits claims of zero trans fats on products containing less than half a gram of those fats per serving.

Increasing the gas pressure at which an oil is hydrogenated reduces trans fats’ formation. But because high pressure is expensive to apply, companies haven’t traditionally explored that avenue, says Fred J. Eller of the U.S. Department of Agriculture in Peoria, Ill.

In several experiments, Eller, Gary R. List, and their collaborators at USDA applied 200 pounds per square inch (psi) of hydrogen gas to batches of soybean oil inside a 2-liter vessel. They simultaneously heated the vessel to between 140°C and 170°C, a range below the temperature used commercially to hydrogenate soybean oil.

The resulting hydrogenated oils contained 16.6 to 17.9 percent trans fats by weight, compared with 39.7 percent trans fats from standard hydrogenation at about 20 psi.

When blended with pure soybean oil, the experimental oils produced soft margarines containing 5 to 6 percent trans fats, which could make a product that qualifies for a label of zero grams trans fats, the researchers point out in an upcoming Journal of Agricultural and Food Chemistry.

Putting the finding into commercial practice would require more than just the new recipe, says List, because the vessels used for industrial-scale hydrogenation would need to be retrofitted to withstand the higher pressures.

That necessity will increase companies’ production costs and make the food products costlier—albeit healthier—for consumers, says food scientist Juan L. Silva of Mississippi State University.

“Retrofitting is not going to be a bank breaker,” says food chemist Dilip K. Nakhasi of Bunge Oils, part of a food-and-agriculture firm in Bradley, Ill. With next year’s labeling change bearing down, he says, companies are “going to lose the customers [unless they] make this minor capital investment.”

The new technique is not the only option, Nakhasi says. Bunge Oils scientists have applied for a patent on a hydrogenation method using a novel catalyst to minimize trans fats. One way or the other, he predicts, many food products will incorporate healthier hydrogenated oils “within months to a year.”

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