“Pink slime” is beef trimmings. Once only used in dog food and cooking oil, the trimmings are now sprayed with ammonia so they are safe to eat and added to most ground beef as a cheaper filler.
The “pink slime” is made by gathering waste trimmings, simmering them at low heat so the fat separates easily from the muscle, and spinning the trimmings using a centrifuge to complete the separation. Next, the mixture is sent through pipes where it is sprayed with ammonia gas to kill bacteria. The process is completed by packaging the meat into bricks. Then, it is frozen and shipped to grocery stores and meat packers, where it is added to most ground beef.