The mammary gland is an astonishing biological factory, with many different cells and structures working together to create, store, and dispense milk. Some components of milk come directly from the cow’s blood and collect in the udder. The principal nutrients, however— fats, sugar, and proteins—are assembled by the gland’s secretory cells, and then released into the udder.
From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee.
By permission of Scribner, a division of Simon & Schuster, Inc.