The loin and tenderloin are two different pieces of meat.
A loin, whether bone in or boneless, is equivalent to a standing rib roast of beef (prime rib). The tenderloin of pork is the same as a tenderloin of beef, where filet mignon comes from.
The tenderloin is the leanest and most tender part of the pig. It should not be braised at all. It is best for fast cooking methods such as pan roasting or grilling.
Actually, the loin has the same cooking requirements as it is also a lean and naturally tender cut as well.
Braising involves cooking meats at low temperatures for long periods of time, partially immersed in a liquid. This cooking method is designed for cheaper cuts of meat that contain a lot of fat and connective and need the long cooking times to tenderize them.
If you want to braise a cut of pork, consider a ham (part of the rear leg) or shoulder cut.
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