Transfer hydrogenation of olive oil works by using a catalyst to help the reaction of the fats in olive oil with hydrogen gas, which bonds hydrogen atoms to available carbon atoms in the fatty acid chains to make them saturated. This results in a fat with a higher melting temperature.
A fully saturated fatty acid has a chain of carbon atoms, with each carbon atom bonded to two other carbon atoms and two hydrogen atoms, except for the last, which is bonded to one carbon atom and three hydrogen atoms. The fatty acids in olive oil are mostly monounsaturated, which means that two adjacent carbon atoms along the chain are each bonded to only one hydrogen atom, but have a double bond with each other. Transfer hydrogenation causes one hydrogen atom to bond with each of these double-bonded carbon atoms, reducing their bond to a single bond and saturating the fatty acid with hydrogen.
The catalyst used to aid transfer hydrogenation is a transition metal, most commonly platinum or palladium. The process can be carried out at normal pressures or at very high pressures in the hydrogen gas. Other sources of hydrogen, including organic substrates such as cyclohexene, are also sometimes used.