I forgot to use a thermometer to check my pork stew. I guess most people don't bother but now worried since I didn't check it after cooking. It looked very well done but had cooled down a bit after waiting to let the pressure release on its own. I cooked it for 28 minutes on the normal pressure setting and seared it beforehand. Recipe was 20-25 minutes. I guess the internal temperature of an instant pot is pretty high so should be okay.
Pressure cookers work by increasing the boiling point of water, and then boiling it. The higher the pressure, the higher the temperature water boils at. The pressures an Instant Pot works at raises the boiling point of water by roughly 20 degrees F at low setting, and 30 at high setting (10 and 15 C roughly). At sea level this is about 230 and 240 F or a little higher (110 and 115C). This is lower than you would roast something in an oven or cook on the stove, but steam-water cooking tends to be faster to raise the temperature and the confined area aids this as well.
In most recipes, the stated time is well into the safe zone as pressure cooking is seldom intended to produce protein that is medium rare for instance. It tends to be more designed to take an item that would typically take a long braise or similar cook and try to produce a similar effect in less time. If you are at altitude, you often need to add time to account for a lower boiling point of water, but otherwise tried and tested recipes should be fairly safe even if you forget to test temp. The thermometer is always the great equalizer to be certain, but as long as the looks, flavor, consistency where all that of fully done pork, then you should be OK.