Final answer:
Hydrogenated vegetable oil in margarine contains both saturated and trans fat, formed through the process of hydrogenation to make oils semi-solid and stable at room temperature.
Step-by-step explanation:
The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. The property of this hydrogenated vegetable oil is that it can contain both saturated fat and trans fat. Hydrogenation makes oils more stable and less likely to go rancid, allowing them to be semi-solid at room temperature, which is ideal for creating margarine that is spreadable and has a longer shelf life. During the process of hydrogenation, trans fatty acids are formed which have an unusual shape making their properties similar to saturated fatty acids. Therefore, while the primary goal of hydrogenation is to convert unsaturated fats into saturated fats, partial hydrogenation may result in the creation of trans fats due to the conversion of some cis-C=C bonds to trans-C=C bonds.