Final answer:
The process of adding hydrogen to unsaturated fat to make it more solid and resist chemical change is known as hydrogenation. This chemical process transforms liquid vegetable oils into semisolid products like margarine and shortening by bubbling hydrogen gas through the oils with the aid of a catalyst.
Step-by-step explanation:
The process of adding hydrogen to unsaturated fat to make it more solid and more resistant to chemical change is called hydrogenation. This process involves the addition of hydrogen atoms to the double bonds of alkenes present in the unsaturated fatty acids of triglycerides. With the help of a catalyst such as nickel (Ni), platinum (Pt), or palladium (Pd), hydrogen gas is bubbled through vegetable oils, converting them from a liquid state to a semisolid or solid state and increasing their melting points. This transformation allows the manufacture of products like margarine and shortening, which are semisolid at room temperature and more stable, with a longer shelf life than their non-hydrogenated counterparts.
During the hydrogenation process, some of the double bonds in the cis-conformation may be converted to the trans-conformation, resulting in the formation of trans-fats, which have different chemical properties than the original cis-fats. Partial hydrogenation of vegetable oils is often preferred as it creates a product with a consistency similar to butter, which is ideal for spreading. Additives such as dyes and flavors are also introduced to mimic butter's color, taste, and odor.