without any carbon-carbon double bonds are abundant (see tallow), but they also can be generated from unsaturated fats by the process of fat hydrogenation. In the course of hydrogenation, some cis double bonds convert into trans double bonds. Chemists call this conversion an isomerization reaction. Hydrogenation of an unsaturated fatty acid is intended to convert unsaturated fatty acids (and unsaturated fats) to saturated derivatives. The hydrogenation process however can cause cis C=C bonds to become trans. Typical commercial hydrogenation is partial to obtain a malleable mixture of fats that is solid at room temperature, but melts during baking, or consumption. The same molecule, containing the same number of atoms, with a double bond in the same location, can be either a trans or a cis fatty acid depending on the configuration of the double bond. For example, oleic acid and elaidic acid are both unsaturated fatty acids with the chemical formula C9H17C9H17O2. They both have a double bond located midway along the carbon chain. It is the configuration of this bond that sets them apart. The configuration has implications for the physical-chemical properties of the molecule. The trans configuration is straighter, while the cis configuration is noticeably kinked as can be seen from the three-dimensional representation shown above. Cis- and trans fatty acids (and their derivatives) have distinct chemical (and metabolic) properties, For example, the melting point of elaidic acid is 45 °C higher than that of oleic acid. This notably means that it is a solid at human body temperatures. In the sense of food production, however, the goal is not necessarily to simply change the configuration of double bonds while maintaining the same ratios of hydrogen to carbon; rather, the goal is to decrease the number of double bonds (when a fatty acid molecule contains more than one double bond it is classified as "polyunsaturated") by increasing the amount of hydrogen (and, thus, single bonds) in the fatty acid. This subsequent lesser degree of unsaturation (and, simultaneously, greater degree of saturation) thereby changes the consistency of the fatty acid by way of allowing its molecules to more greatly compress and congeal and in turn thereby makes it less prone to rancidity (in which free radicals attack double bonds). In this second sense of the goal being to simply reduce the degree of unsaturation in an unsaturated fatty acid, the production of trans fatty acids is thus an undesirable