Why is it called “bulk”? The answer is primarily a matter of scale. In a high-volume bakery setting, bakers mix enormous amounts of dough in order to produce dozens of loaves. Handling individual portions of dough over the lifetime of the baking cycle is inefficient, time-consuming, and takes up too much space in the kitchen. Instead, bakers let an entire mass of dough ferment before dividing and shaping into individual loves. This process ensures consistent and predictable fermentation for several reasons: Chiefly, a larger mass of dough is more temperature-stable, and the baker only has to pay attention to one mass of dough as opposed to several dozen at a time. For home bakers baking one loaf at a time, bulk fermentation in this manner is not necessary. But even if you’re scaling up a batch of dough to bake two or more of the same loaf, it can be helpful to bulk en masse prior to dividing and shaping.
Some bakers refer to this stage as the ‘proof’ stage. Others, like Trevor Wilson, distinguish bulk fermentation from bulk proof. Bulk fermentation starts when the levain is mixed into the dough (which can occur before the dough is fully mixed); the proof stage starts when all ingredients (such as salt) are incorporated. Proof highlights the point at which the dough begins to rise—underscoring the transition from aggressive kneading or mixing to more gentle dough handling and folding as the dough slowly rises.
