The fork poking hole trick is more useful with collagen casing as they're more likely to burst. But a pin hole for air bubbles is one I've seen in a number of sausage books. The air expands the more than the meat when heated which often ruptures the casing. The pin holes themselves are small enough to not effect juiciness when cooking.
This is more about people stuffing at home who aren't real good at stuffing sausage. I can get a good stuff if I have someone else to help me, but when I do it alone, I get air bubbles between trying to work the plunger and feed casings at the same time. May also have something to with equipment. I'm using a home style Kitchen Aid and their grinding/stuffing attachments.
Phil |