why do we engineer trans fat?

Answer 1

Trans fat was not intentionally engineered. It comes from the hydrogenation of unsaturated vegetable oils (which are liquid) to produce solid saturated fats. These fats are more stable and won't go rancid as fast as the liquids, and improve the food texture. Most natural solid fats, such as butter, contain saturated fats, mono-unsaturated and poty-unsaturated fats, but have a high percentage of saturated fats. They have some trans fats (which are mono-unsaturated), but very little. The artificial hydrogenation process, if it were 100% effective (converting all the fat to saturated fat) would produce no trans fats. But the process is not 100%, and some fats are left in the mono-unsaturated form. (Sometimes it is intentionally incomplete to produce a softer product; these are called partially hydrogenated fats, and are the most commonly used.) Unfortunately, most of those incompletely saturated fats are the trans variety, unlike the natural fats.