Originally Posted by eipstudios

The bun alone contains 34 ingredients, says Meredith Melnick at TIME. In addition to chemicals like ammonium sulfate and polysorbate 80, the most egregious may be azodicarbonamide — "a flour-bleaching agent most commonly used in the manufactur[ing] of foamed plastics like gym mats and the soles of shoes." According to McDonald's own ingredient list, the bun also includes calcium sulfate and ethoxylated mono- and diglycerides, among other chemicals.

So what's the meat made of?
Pig innards and plenty of salt. Typically, "restructured meat product" includes pig bits like tripe, heart, and scalded stomach, says Whet Moser at Chicago Magazine, citing a 1995 article by Robert Mandigo, a professor at the University of Nebraska. These parts are cooked and blended with salt and water to extract salt-soluble proteins, which act as a "glue" that helps bind the reshaped meat together.