What effect does hydrogenation have on fats?

Hydrogenation is a chemical process that involves adding hydrogen atoms to unsaturated fats, which are typically liquid at room temperature, to convert them into saturated fats that are solid or semi-solid. This change in structure not only impacts the physical state of the fat but can also change its properties, such as texture and shelf life.

By making oils more solid, hydrogenation improves the stability of the fat, making it more suitable for various food products such as margarine or shortening, which require a solid form. This process can also alter the melting point of the fat, influencing how it behaves in cooking and baking.

While hydrogenation can have other effects, such as altering flavor or affecting nutritional content, the key characteristic of this process is its ability to transform liquid fats into solid forms, which is why the correct answer is the change from liquid to solid.