First, let me say thar I'm grinding fresh polish sausage that will not be smoked. The recipe calls for 1 tsp Instacure for each 5# of meat. Do I really need this, since I'm not going to smoke it? Is it just to manage color?
If you are making sausage fresh for eating right away and freezing the rest you do not need any cure. The cure is used to keep bacteria from making your product unsafe to consume after the smoking or drying process.
As Bear stated you don't need to, but you may want to add the same amount of pickling (table) salt that is equivalent to the amount of Instacure, to maintain the salt level the author of the recipe intended.
If the recipe itself did not include steps for smoking, it is probably for color, but also the author of the recipe may have added the cure for flavor. Leaving the cure out will effect the color, and taste. That is one of the reasons I prefer fresh sausage, because I don't particularly care for the flavor that the cure adds to smoked sausage.
That's pretty much what I was thinking. I've got a couple of friends that have problems with nitrates, so I'll taste and adjust the salt & save the Instacure for another day. Thanks, guys!