Here's the definition that's on our security deposit page, which doesn't get into the nitty-gritty: Normal wear and tear is a term that Wisconsin law does not define.
(3)Protein Fat-Free Percentage, Protein Fat-Free Content, PFF Percentage, PFF Content or PFF of a product means the meat protein (indigenous to the raw, unprocessed pork cut) content expressed as a percent of the non-fat portion of the finished product.
In 1982, a final rule published by FSIS on mechanically separated meat said it was safe and established a standard of identity for the food product. Some restrictions were made on how much can be used and the type of products in which it can be used.