Pork loins can also vary in size and thickness. So cooking times will vary greatly, particularly if you bought the tenderloin, which cooks much faster. Cook the loin roast or pork tenderloin longer if it's large or thick. If you are unsure on how long to cook your particular roast, cook the pork loin until it reaches an internal temperature of 145°F in its thickest part. The higher the temperature, the drier the loin will be, so don't go past 145°F while in the oven too much if possible. You can use a slow cooker too and if it has a sear or saute function like the Instant Pot has, then even better!
Season pork with salt and pepper. Turn Instant Pot on "Sauté”, and add butter and melt. Add the pork loin and sear the sides of the pork loin to a nice golden brown. Add the onions and garlic and cook until soft, about 2 minutes.
Stir in the carrots, celery, broth or apple juice, Worcestershire sauce, brown sugar, mustard, and herbs.
Close the lid, set to high pressure, and after the pressure cooker reaches full pressure, cook for about 30 minutes *depending on size & preferred doneness. (These are the steps we did for our Instant Pot: Press "Cancel" to stop the "Sauté" setting. Press the "Manual" button. Set the time to 30 minutes.)
After the cooking time is complete, press "Cancel" and carefully release the pressure. If possible, check the internal temperature of the pork loin (it should be about 145°F).
Remove the pork loin from the Instant Pot (keep the juices the Instant Pot), cover and allow the pork loin to rest for about 10 minutes, depending on how large your loin roast is and how well done you like it.
Mix together the cornstarch and water. Add to the Instant Pot with the juices. Turn Instant Pot on "Sauté” and simmer until thickened. Taste seasoning and add additional salt and pepper if desired.