Why are oils bleached during processing?

Oils are bleached during processing primarily to remove unwanted color and impurities that affect the quality of the final product. Many nonglyceride components, such as chlorophyll and carotenoids, contribute to the color and flavor of fats, which can be undesirable for both edible and industrial applications.12

To achieve color removal, heated oils are treated with bleaching agents such as fuller’s earth, activated carbon, or activated clays. These materials adsorb impurities, which are then removed through filtration. Additionally, oils can undergo heat bleaching, where temperatures exceeding 175 °C (347 °F) decompose certain pigments into colorless materials.1

While bleaching improves the appearance of the oil, it can also reduce the oil's resistance to rancidity because the process often removes natural antioxidants along with the impurities.1