I recently picked up a new cook book (new to me) called "Wisconsin Country Cookbook and Journal". It has a lot of really great recipes and ideas for cooking. The only problem is I come across this ingredent "alum" and I have no idea what it is. I look it up, and it says something about being a pickling agent, but one that isn't used much anymore due to the fact it can cause stomach discomfort. What exactly does it do and is there a replacement out there for it.