A mixture of tallow and other fats was saponified by an alkali. Phospholipids can be saponified, which releases the fatty acids contained in their diglyceride tail. The ester is then saponified to the corresponding carboxylic acid (5). Vegetable oils and animal fats are the traditional materials that are saponified. Soap is made from saponified oil, and many cosmetics contain peanut oil and its derivatives.