I've tried to make various types of sausages a few times, and lately decided to try again. In the past I've been frustrated by the casings. They would break, and stuffing the sausage into the casings seemed to be an enormous labor, dwarfing the whole rest of the process, and leading to great frustration. So I wonder, why are they necessary?
I made an emulsified sausage from Ruhlman's book, Weisswurst, and instead of putting it in a casing I put it in a sous vide bag and cooked it at 150. That seemed to work reasonably well. Some fat came out in the bag, but not a lot, and the sausage was delicious--better than anything I've made before. But when I tried the same thing with a non-emulsified sausage, an enormous amount of fat came out of the meat in the bag. Why put that fat in there if it won't stay? I tried another recipe ("veal terrine") that was emulsified and I think the entire amount of backfat the recipe called for ended up pooled up in the bag rather than on my plate. I also wonder also if I lose the same amount of the fat when pan frying bulk sausage---often times quite a lot of fat comes out on the pan.
Is it reasonable to try to avoid using normal casings and instead using the sous vide bags? And how can I keep the fat from separating from the meat?