The corn used to make most oil is yellow dent corn, also called field corn—a different variety than the sweet corn you find at the grocery store. A medium ear of dent corn has about 4.74 grams of fat. Most of that is contained in the germ, the innermost part of the kernel. (A medium ear of sweet corn has about 1.06 grams of fat, though it still qualifies as low fat under FDA guidelines.)

It takes a lot of corn to make corn oil. A 56-pound bushel yields 1.6 pounds, or about 700 milliliters, of oil, says Shannon McNamara, spokeswoman for the Corn Refiners Association.

In corn refining , the kernel is separated into its component parts: the fiber-rich outer hull, the starch-and-protein-rich endosperm, and the oil-rich germ. To do this, the kernels are steeped in slightly acidified water, which loosens the hull and makes the endosperm swell up; then they’re ground coarsely. A centrifuge removes the lighter germ from the rest of the corn. The remaining grounds are passed through a series of screens. The endosperm, which grinds into small particles because it’s soft, passes through the screens. The larger pieces of hull stay behind.

After being cleaned and dried, the germ is pressed to extract the oil, much in the same way olives or canola seeds would be. Most producers then use a solvent such as hexane to extract more oil from the pressed germ.

At this point, the oil is called crude corn oil and is dark yellow with a strong corn smell and taste. It’s filtered, bleached, and cleaned to purify it, resulting in the light-yellow, neutral-smelling refined corn oil you’ve got in your pantry.