Trans fatty acids are unsaturated fatty acids containing at least one double bond in the trans configuration, formed when edible oils are partially hydrogenated. This process is normally done to increase the melting points of the fatty acids to enable liquid oils to be used in solid fats formulations such as margarines, shortenings, vanaspati and bakery fats. The conformation of the double bond(s) impacts the physical properties of the fatty acids. Those fatty acids containing a trans double bond have the potential for closer packing or alignment of their acyl chains, resulting in decreased mobility and reduced fluidity compared to natural fatty acids containing a cis double bond. Partial hydrogenation of edible oils causes isomerization of some of the remaining double bonds, resulting in an increase in the trans fatty acids content and hardening of the fat.