Purdue University researchers have developed a hydrogenation process that could solidify soybean oil for food processing without creating trans fats, which have been linked to heart disease and stroke.
Hydrogenation is a chemical process that transforms liquid vegetable oil to a solid or semisolid state—useful for creating food products like vegetable shortening and margarine. However, the intense heat required in the conventional hydrogenation process causes the formation of the harmful trans fats.
Because of this, the U.S. Food and Drug Administration removed partially hydrogenated oils (PHOs) from the list of safe foods in 2015. Some food manufacturers now use palm oil and other imported oils that do not require hydrogenation, rather than less-expensive soybean oil.
To maintain demand for soybeans in the U.S. food market by safely producing PHOs, former Purdue professor and food scientist Kevin Keener, now director for the Center for Crops Utilization Research at Iowa State University, and doctoral student Ximena Yépez have developed a process known as high-voltage atmospheric cold plasma (HVACP) hydrogenation. This process occurs at room temperature, avoiding the high temperatures that cause trans fats to form.
Traditional hydrogenation processes rely on a catalyst, high pressure and high temperatures to separate molecular hydrogen into atoms. The HVACP process bypasses the catalyst and uses high-voltage electrical discharges to separate the molecules. Once the hydrogen molecule is split, each atom attaches to the double bonds between the molecules in the oil, giving them more structure. More structured molecules cause the oil to become more solid, or "saturated."
The HVACP experimental design consists of a small amount of oil inside a plasma-filled container, which is then placed in a bag filled with a hydrogen-blend gas. As the gas fills the bag, two electrodes discharge up to 90 kilowatts of electricity through the chamber, splitting the hydrogen molecules in the gas into ions. These ions bond with the double bonds in the fatty acid molecules on the surface of the oil.
Currently, a typical hydrogenation reaction might produce only a 3% increase in saturated fatty acids while increasing the formation of trans fats by up to 40%. But after a 12-hour HVACP treatment, the oil showed a 32.3% increase in saturated fatty acids and no trans fats. This ratio not only means that the finished product is safer for human consumption, Keener says, but also that the HVACP treatment is more efficient than traditional processes.
The researchers say that two primary obstacles still exist in adapting the process for commercial use. The first is that the HVACP procedure yields a small amount of byproduct that the researchers have not yet identified. This could be an alternative form of trans fat or a similar substance, says Yépez.
The second obstacle is speed. While the process creates more product than heat-based hydrogenation, it is much slower. Yépez and Keener are trying several approaches to make the process faster, including increasing the amount of electricity discharged through the chamber and spraying the oil into the chamber as droplets.
"Some of the methods we're investigating could reduce hydrogenation time to a matter of minutes," Keener says. "Then you could replicate these modules—create a hundred or a thousand of them. And the process isn't just limited to food oils. We can manipulate the chemistry of any oil, plant-based or industrial."