About a couple days ago, I set my circulated waterbath to 60C and dropped in two racks of pork side ribs. While it sank initially, much to my dismay, I found the middle portion of it floating recently. The ribs were already sold in a vacuum packed pouch so I didn't bother repackaging them. I'm concerned that the portion floating could be a result of bacterial fermentation (so the ribs were already bad when I bought them). However, if it simply floated as a result of steam buildup, is it safe to consume? My setup is an 18qt roaster with a covered lid, circulated by an aquarium pump and managed through a Dorkfood DSV. Since it is covered, I took a thermometer and tested the temperature of the air below the lid and it read up to 57C, ensuring safe pasteurization temperatures. However, since the bag inflated, is it safe to assume that the middle portion received adequate heat transfer to achieve pasteurization?