Just to clarify a few things, IDY is best added directly to the flour, but when it does need to be prehydrated it should be prehydrated in a small quantity of water at 95F (manufacturer's recommendations) we confirmed this using instrumentation in our laboratory. If the temperature of the water is as little as 5F on either side of the 95F recommendation some gassing power of the yeast will be lost. Cold water is a real bummer with IDY since it will extract glutathione from the yeast for a double whammy, loss of yeast activity and a softer dough (glutathione is an amino acid contained within the yeast cell that when extracted has the same effect upon the dough as L-cysteine (think PZ-44). This is actually sold as "dead yeast" where it is used as a dough relaxer to reduce the elasticity of the dough. When the dough is only allowed to cold ferment you can go too low on the yeast level, this is due to the fact that all of the yeast is typically not working for you in a cold ferment situation unless you allow the dough to fully warm after removal from the cooler, which is counter productive in a pizzeria where you need to have the dough last for several hours after it is removed from the cooler. When you make your dough as "fresh" dough it is not refrigerates, hence all of the yeast is working to leaven the dough so there is less chance of developing the "dreaded gum line". What is a gum line? A gum line is defined as a gummy, somewhat under baked portion of the dough located directly under the sauce. It can range from 1/16 to 1/8-inch thick, and it looks something like a layer of pasta directly under the sauce. There are two ways to ascertain if you have a gum line. 1) Cut a slice from the pie and tear it down the middle from heel (rim/edge) to the point observing the way the dough cleaves as you pull it apart. If the dough stretches and pulls rather than tearing cleanly, congratulations, you have a gum line. The way I like to use is to turn a slice upside down and carefully cut it using a sharp knife (Exacto Knife or a box cutter) and light strokes to cut through the bottom crust. Once you have cut the slice in half (heel to point) pick up one half and carefully look at the area just under the sauce. A paper thin layer of discolored dough (about the thickness of a business card) is perfectly normal, if it is any thicker you are looking at a gum line. Why do we call it the "dreaded gum line? Because there are so many different things that can cause it (I've written several good articles on the topic in PMQ/In Lehmann's Terms) and until you find the right cause, you can't get rid of it. Why all the fuss? A gum line detracts from the eating characteristics of the pizza, and in a DELCO situation it contributes to unacceptably tough, chewy eating characteristics that won't go away. If you are going to eat the pizza while still fresh and hot out of the oven you might not even notice the gum line, thinking it is just a tougher, more chewy pizza. There are a whole raft of things that can cause the gum line development and these are all discussed in my articles.
Tom Lehmann/The Dough Doctor