Fermentation

Fermentation is the backbone of bread. When yeast and bacteria consume the sugars in flour, they produce CO2 gas (which creates bubbles, rise, and an open crumb), organic acids (lactic and acetic, which create flavor and tang), and enzymes (which break down starches and proteins, improving texture and digestibility).

Without fermentation, bread is a cracker. Everything else in the bread-making process — mixing, folding, shaping — is in service of fermentation.

Bulk fermentation is the main fermentation phase, after mixing and before shaping. It's called "bulk" because the dough ferments as one mass before being divided and shaped.

During bulk, the dough should grow 50–75% in volume, develop a domed surface, feel airy and jiggly when you shake the container, and show bubbles on the sides and surface. The dough should smell pleasantly sour and yeasty.

Duration varies widely: 4–6 hours at 75°F (24°C), 8–12 hours at 68°F (20°C). Temperature is the primary variable. A few degrees makes hours of difference.

The poke test: Wet your finger and poke the dough about ½ inch. If it springs back slowly and incompletely, bulk is done. If it springs back immediately, it needs more time. If it doesn't spring back at all, it's overfermented.

Volume: 50–75% growth is the target. Use a straight-sided container and mark the starting level with a rubber band.

Texture: The dough should feel lighter and more airy than when you started. It should jiggle when you shake the container.

Underfermented: Dense crumb, gummy texture, little oven spring, bland flavor. The most common beginner mistake. When in doubt, give it more time.

Overfermented: Slack, sticky dough that's hard to shape. Flat loaf with little oven spring. Sour, acidic flavor. The dough may smell strongly of alcohol.

Underfermentation is more recoverable than overfermentation. If you're unsure, err on the side of more time.