Is the process of adding hydrogen molecules directly to an unsaturated fatty acid from sources such as vegetable oils to convert it to a semi-solid form such as margarine or shortening. Hydrogenation contributes important textural properties to food. The degree of hydrogenation influences the firmness and spreadability of margarines, flakiness of pie crust and the creaminess of puddings. Hydrogenated oils are sometimes used in place of other fats with higher proportions of saturated fatty acids such as butter or lard.