Some of the old books describe bull flour as 1/2 wheat flour and the rest equal measures of corn, rye, and rice flours. I made a test batch using
tdimler's lockhart sausage with 860 g well-trimmed chuck ($2.99/lb on sale at Winn Dixie!), 150 g unsmoked pork belly from Costco, Alderwood smoked salt (I don't have a smoker, but smoke is smoke), Prague #2, the peppers, and binder as all-purpose flour, cornstarch, rye flour and rice flour. Hog casings. Under ice for 2 hours. Sous vide one hour at 65 degrees C, then to the grill on indirect heat. Wonderful. The last time I ate at Kreuz and Blacks was over 25 years ago when we lived in Austin. Memories fade, but this is a keeper.
Why would this binder work? I suppose the flour mixes with the fat and water to make a roux. The cornstarch is a well-known thickener in cooking. Rye flour makes a sticky mess mixed with water. I have no clue that the rice flour does.