Just to add: I assume you're creating your own solution, injecting and massaging it in. A good rule of thumb (and max that is effective) is one half of one percent of the weight of the meat. Three tenths of one percent by weight of salt if you are using just phosphate. Be sure you're using a food grade phosphate, seems the better (at least more expensive ones) are from German sources.
TSP doesn't really tenderize, but allows the proteins to bond with more water, resulting in a "juicier" product. This can make lesser, tougher cuts more appealing. Crappy dried out meat, with a poor mouthfeel
Old dairy cow, properly injected, and then prepared
Seafood applications are popular as well. Plumped up shrimp are more appealing (and weigh more)
