Hi, I made 2 batches of sausage, Polish sausage 2 dayes ago, & Old Fashioned sausage yesterday..I used the seasonings purchased from a sausage supply place.. The Polish was stuffed into Collagen casings, & the Old Fashioned was stuffed into hog casings. using my electric grinder with stuffing tubes attached.. . They were both smoked in my GOSM propane smoker starting around 120 degrees & finished at 225 degrees, Mesquite wood was used for smoke in both.. Both batches turned out well, & taste excellent, BUT, when the rings are cut in both batches the centers are dark the entire length of the rings.. I used to go to my friend's place to make sausage & he only had a homemade smoker, plywood, & built an oak fire on a dirt floor, & never had this problem.. what am I doing wrong??