Corn oil is oil extracted from the germ of corn (maize). Its main use is in cooking, where its high smoke point makes refined corn oil a valuable frying oil. It is also a key ingredient in some margarines. Corn oil has a milder taste and is less expensive than most other types of vegetable oils. One bushel of corn contains 1.55 pounds of corn oil (2.8% by weight). Corn agronomists have developed high-oil varieties; however, these varieties tend to show lower field yields, so they are not universally accepted by growers. Refined corn oil is 99% triglyceride, with proportions of approximately 59% polyunsaturated fatty acid, 24% monounsaturated fatty acid, and 13% saturated fatty acid. Corn oil is also one source of biodiesel. Biodiesel is commonly made from soybean or rapeseed oils, but as corn oil refining technology improves, it is expected to become a greater source of biodiesel and a backup source in case of large-scale soybean crop failures. Other industrial uses for corn oil include soap, salve, paint, rustproofing for metal surfaces, inks, textiles, nitroglycerin, and insecticides. It is sometimes used as a carrier for drug molecules in pharmaceutical preparations. The first commercial corn oil for cooking purposes was extracted in 1898 and 1899 by machinery invented by Theodore Hudnut and Benjamin Hudnut of the Hudnut Hominy Company of Terre Haute, Indiana, and called "mazoil." Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container.