There are a few ways to tenderize ribs. One is by boiling them for 30-45 minutes before cooking them. Parboiling something is just boiling it, but stopping before it's fully cooked.I would suggest other ways to cook your ribs, though, if you have the time. Slow cooking them in a crock-pot, oven or BBQ will give much better results. On the BBQ or oven, you can put them in tinfoil with some apple juice & brown sugar and cook on low heat ~250ish for 4 or more hours, until they start to fall off the bone. Then remove from tinfoil and cook on higher heat, basting with your favourite BBQ sauce & flipping several times.