Although similar and both cuts of pork, loin and tenderloin aren't the same and aren't interchangeable in many recipes. They're visibly quite different. Tenderloin comes in a long, thin shape and is usually less than 3 inches across, with very little fat. Pork loin is thick and wide and has a strip of white fat running along it. It would work but it's better to use tenderloin. If you really want to use loin though, you'll need a longer cookie time.