So this story is kind of repulsive and certainly won't make you hungry for a juicy hamburger or steak, but it's a part of food history so here goes:
On June 30, 1906, President Theodore Roosevelt signed into law the Meat Inspection Act and Pure Food and Drug Act which provided for federal inspection of meat products and prohibited the manufacture, sale, or transportation of adulterated food products.
The Acts arose in part due to articles and exposés written by muckrakers, like Upton Sinclair, whose popular 1906 novel The Jungle contains hair-raising descriptions of the ways in which meat was produced in Chicago slaughterhouses and stockyards.
Sinclair described how dead rats, putrid meat, and poisoned rat bait were routinely shoveled into sausage-grinding machines, how bribed inspectors turned a blind eye when diseased cows were slaughtered for beef, and how filth and guts were swept off the floor and then packaged as “potted ham.”
Muckraker, of course, is a term that is applied to those novelists and journalists who sought to expose the corruption of American business and politics in the early twentieth century. The term was first coined by President Roosevelt in a 1906 speech in which he compared writers like Sinclair to the “Man with the Muck-rake” (a character in John Bunyan's Pilgrim's Progress) who was so focused on "raking the filth at his feet” that he failed to look up and “behold the celestial crown.”
Similarly, Roosevelt argued that Sinclair and other muckrakers were so focused on the evils of American society that they failed to behold “the vision of America's promise.”