I made some sweet potato butter in the crockpot overnight and canned it this morning. I was careful to keep everything hot and sanitary until the butter was safely stored away in the jars, but I'm still not sure all went well.
The trouble is bubbles. I went around the inside edge of each jar with a thin knife to remove bubbles before putting the lids on. But when processing was done (the lids had sealed while still in the boiling water) I saw bubbles, sometimes big ones, at the bottom of some of the jars. I know the butter was thin enough to allow bubbles to rise during processing, so I'm not afraid that they're full of dirty unsterile air that couldn't boil its way out. I think it's just that, although I put the sweet potatoes through the food mill twice (once before adding the rest of the ingredients and once near the end of cooking), the butter is still slightly chunky and doesn't adhere perfectly smoothly to the walls of the jar.
I've seen some bubbles even in commercially canned jams, so I suspect it's OK. Opinions please?