If I wanted to cold ferment any pizza dough, from 24-48 hrs, how would I determine the yeast and hydration amounts?
Also, I've seen some references regarding over-fermentation. How do you know if that has occured?
Yeast activity is affected by temperature, time, minerals in the water, yeast age and by salt and water in the dough, along with a host of other factors. Determining exactly how much yeast to use to ensure that your dough is ready exactly when you need it is probably one of the most difficult aspects to baking. I can establish a yeast quantity that will work perfectly for me, with my environmental variables, but if I give this recipe to you, it might not be ready in the same amount of time because your environment is different.
The only way to master it is to do it. Use the yeast figure in the recipe, ferment it the time they specify. If the dough doubles in that time frame, you're good to go. If it doesn't, then give it more time and/or a higher temp. If it more than doubles and/or begins to deflate, then, next time, either use less yeast or a lower temp. Record everything- recipe, water temp, air/flour temp, dough temp, yeast age, time out of fridge, time in fridge. As you make more and more dough, you'll have more data to refer to when you want to change something up and you'll be in a better position to be able to predict yeast behavior.
Determining hydration is another area where you can just work with what the recipe tells you (adjusting for the protein content of your flour), but if you really want to master pizzamaking, you've got to dive in and experiment with varying quantities of water and see what kind of impact they have on the finished result. For every oven setup/bake time, flour and recipe, there's going to be a hydration level that gives you optimal oven spring. Like, yeast, a recipe author can give you a ballpark, but they won't have your oven, and, if you want a perfect end result, you'll have to tweak the water content until the oven spring is optimal. Hydration also has a strong subjective aspect. Some people prefer the taste of lower hydration doughs while others prefer higher hydration doughs. Dive in, play around and see what you like.
Over fermentation is a subject that is both complicated, personal and style specific. For NY, I like doughs that have doubled in a 48 to 72 hour time frame. You will find some that like to push their doughs farther. Many people consider deflated dough to be overfermented, but it really depends on the fermentation time. Unless the dough has been fermented for quite a few days, deflated doughs can generally be re-balled and will bake up just fine. If at all possible, it's best to use an amount of yeast that will double your dough in your desired time frame, and not take it to a point of deflation, though.