While yeast is a simple, single cell organism, what it does in a dough is rather complex. In addition to the yeast feeding on available carbohydrates, producing acids, carbon dioxide and alcohol as byproducts, the yeast also provides a source of enzymes such as amylolytic and proteolytic that break-down starches and proteins respectively.
Initially, when the dough is first placed into the cooler, fermentation continues along at a happy pace until the dough temperature begins to drop. As the temperature of the dough approaches 45 F, the rate of fermentation drops off dramatically. By the time the dough temperature has come down to box temperature (36 to 38 F), essentially no further fermentation is taking place. The dough is continuing to change as long as it is stored in the cooler. Those acids that were formed during the time the dough was fermenting are still present, and will slowly act on the flour proteins to weaken them, making the dough softer and more extensible. Ditto for the enzymes. The proteolytic (protease) enzymes will slowly hydrolyze the flour proteins, also contributing to a softer, more extensible dough. The amylolytic (amylase) enzymes are slowly converting starches to sugars (dextrins) for the yeast to feed upon. But since the yeast isn’t actively feeding due to the depressed temperature of the dough, there can be an excess of these sugars, resulting in a sticky dough characteristic. These conditions continue throughout the refrigerated life of the dough.
In a normal pizza dough, with about 1.5 percent yeast (as compressed yeast), these conditions do not reach an intolerable level until about the 4th (or possibly even the 5th) day of refrigerated storage. At this point, we usually find the dough has become excessively soft, it collapses at the slightest provocation, and is rather sticky to the touch. When we bake the formed dough piece, the resulting crust may lack the necessary strength to exhibit rise in the center of the pizza and the edges might also fail to rise, resulting in what is affectionately known as a “knife edge.” Overall, the crust might look more like a pancake than a pizza crust. This degradation of the dough will continue, until at some point the dough will be too soft and weak to do anything with and must be discarded.