Fatty acids (FAs) are the main components of lipids, and the physical, chemical, and physiological properties of lipids mainly depend on their fatty acid composition. The composition of fatty acids is determined by gas chromatography of methylated fatty acids. Trans fatty acids are a type of unsaturated fat that occur in small amounts in nature, but have been widely industrially produced from vegetable fats since the 1950s for use in margarine, packaged baked goods, snack foods, and fried fast food.