I got a 8qt Presto Pro pressure cooker for by birthday, and tried it out tonight with 3 lbs choice short ribs. For the liquid I used 1cup beef broth and 1cup orange juice and also added a 1/2 cup brown sugar (2 cups liquid was recommended in the booklet). After the 25 minutes, the ribs were perfectly cooked, but the liquid was heavily caramelized and burnt on the bottom. I ended up adding some more orange juice and stock to the remainder and reducing a little to salvage the sauce (I probably wouldn't have served the sauce if company was present). I had my electric stove top on about 6 (I know that is extremely relative) - I had a steady flow of steam. Was it the excess sugar that caused this? Did I not use enough liquid?
Any advice from those with more experience would be appreciated. TIA.