The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

“First we separate the corn into its botanical parts—embryo, endosperm, fiber—and then into its chemical parts,” Johnson explained as we began our tour of the plant. When a shipment of corn arrives at the mill, it is steeped for thirty-six hours in a bath of water containing a small amount of sulphur dioxide. The acid bath swells the kernels and frees the starch from the proteins that surround it. After the soak, the swollen kernels are ground in a mill. “By now the germ is rubbery and it pops right off,” Johnson explained. “We take the slurry to a hydroclone”—basically a centrifuge for liquids—“where the germ floats off. After it’s dried, we squeeze it for corn oil.” Corn oil can be used as a cooking or salad oil, or hydrogenated for use in margarine and other processed foods: Atoms of hydrogen are forced into the fat molecules to make them solid at room temperature. (Though originally designed as a healthy substitute for animal fats, medical researchers now think these trans fats are actually worse for our arteries than butter.) Once the germ has been removed and the kernels crushed, what’s left is a white mush of protein and starch called “mill starch.” To draw off as much of the protein as possible, the mill starch undergoes a progressively finer series of grindings and filterings and centrifuges. The extracted protein, called gluten, is used in animal feed. At each step more fresh water is added—it takes about five gallons to process a bushel of corn, and prodigious a...