Hydrogenating natural oils without risking unhealthy trans fats

January 25th, 2009 - 5:22 pm ICT by IANS  

Washington, Jan 25 (IANS) Manufacturers add hydrogen to natural oils to prolong shelf-life of foods in a process called hydrogenation. But the process also causes production of trans fats, which are linked with raising bad cholesterol and increasing the risk for coronary heart diseases. Trans fats are found in vegetable shortening, some types of margarine, crackers, cookies and snacks. Health authorities worldwide recommend that people reduce their consumption of these fats.

Now University of California -Riverside (UC-R) chemists have designed a catalyst - a substance that accelerates a chemical reaction - that allows hydrogenated oils to be made while minimising production of trans fats.

In their experiments, the researchers, led by Francisco Zaera, professor of chemistry, used platinum, a common catalyst for these processes. By controlling the shape of the platinum particles, the group was able to make the catalyst more selective.

Catalytic selectivity refers to the ability of a catalyst to select a specific pathway from among many possible chemical reactions. In the case of the researchers’ experiments, selectivity refers to the production of partially hydrogenated fats without the formation of trans fats.

Zaera’s lab found that the platinum catalyst performed most selectively when its particles assumed tetrahedral shapes, with the atoms arranged in a hexagonal honeycomb lattice.

Particles with these shapes allow for the preservation of the harmless configuration in the hydrogenated fats. Other lattices, the researchers found, favour the production of trans fats.

Platinum catalysts such as those used by the Zaera group are considered heterogeneous because they exist in a different phase (solid) than the reactants (liquid or gas).

Compared with homogeneous catalysts, where the catalyst is in the same phase (liquid) as the reactants, heterogeneous catalysts have the advantages of easy preparation, handling, separation from the reaction mixture, reuse, high stability, and low cost.

But their main disadvantage is that, unlike homogeneous catalysts, which tend to be molecular, heterogeneous catalysts must be dispersed as small particles in a high surface-area support in order to optimize their use. This typically results in catalysts with surfaces of ill-defined structures.

The research by Zaera and his colleagues is a breakthrough also because it shows for the first time that it is possible to achieve selectivity with heterogeneous catalysts like platinum by controlling the structure of their surfaces, said an UCR release.

Nearly 80 percent of all chemical industrial processes use catalysts. With annual global sales of about $1500 billion, catalysts contribute approximately 35 percent of the world’s gross domestic product. They are used in the manufacture of commodity, petro- and agro-chemicals, pharmaceuticals, cosmetics, foods, and polymers.

The results appeared online earlier this week in Nature Materials.

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