Mixing and baking bread from scratch can take several hours, but that time includes relatively little hands-on work. Mostly you're able to do other things, because the yeast and the flour don't require your supervision once they're mixed. They'll go about their business and leave you to yours until the bread is fully risen. Of course, the adage "out of sight, out of mind" applies to bread dough, and if you forget about the dough and let it rise overnight the results can be unfortunate.
The rise of bread dough is called "fermentation" by professionals because it's exactly the same process that takes place when alcohol is produced. The yeasts in your bread consume sugars and give off both alcohol and carbon dioxide, and they can turn grain into either beer or bread with equal deftness. In bread, alcohol production is minimized and the carbon dioxide is trapped by the stretchy dough. The dough's elastic network of proteins called gluten contains the gas as it accumulates, causing the dough to rise and soften. If the dough isn't punched down and kneaded at the correct time, the yeast will begin to overferment.
Some breads are intended to rise slowly overnight, but most home bakers use quick-rising recipes. Those recipes use more yeast than slow-fermenting doughs, and they're intended to rise for only an hour or two. If you forget a quick-fermenting dough overnight, the yeasts will quickly exhaust their available supply of sugars. They'll produce undesirable quantities of alcohol, weakening the bread's gluten and coarsening its texture. Naturally occurring bacteria in the flour will digest part of the alcohol, turning it into lactic and acetic acids that give the bread a distinctively sour and unpleasant texture, and further weaken the gluten. If you bake it, you'll get a dense, coarse, poor-tasting loaf.
Salvaging Your Dough
Although overfermentation is a bad thing, long fermentation time does have benefits as well. The natural bacteria and enzymes in the flour have time to break down its starchy carbohydrate molecules, releasing the natural sugars and creating new, complex flavor molecules. Even though you can't bake your overfermented dough, you can use a portion of it as a starter to add those complex flavors to a new batch of bread. Mix up the batch as you normally would, then add up to a quarter of the old dough and mix it thoroughly into the new batch. Your bread will have a richer, deeper flavor and the crust will brown to a deep red-gold when it's baked.
If your bread-baking is interrupted, you can minimize the risk of overfermentation by covering the dough and putting it in your fridge. This slows or "retards" the fermentation. When you get back to baking, you can punch down the dough, bring it up to room temperature, and continue. On the other hand, if a slow overnight rise in the refrigerator fits better into your schedule, you can deliberately make slow-fermenting bread. Cold-fermenting recipes call for less yeast, which slows the fermentation process. That allows you to reap the flavor benefits of a slow rising process, without the unpleasant effects of overfermentation.
- On Food and Cooking: The Science and Lore of the Kitchen; Harold McGee
- The Bread Baker's Apprentice: Mastering the Art of Extraordinary Bread; Peter Reinhart
- Photo Credit Thinkstock/Comstock/Getty Images