Slow bread is a type of bread based on a 6,000-year-old process of baking using a slow-fermented combination of flour, water, and a very small amount of yeast. Typically, this mixture is allowed to ferment for 18 hours before it is baked. The resulting bread is hearty with a thicker crust and an open crumb, similar to the rustic breads available at modern-day artisan bakeries. Slow bread can be called by various names, including slow rise bread, slow proofed bread, or no-knead bread. Many forms of rustic or artisan breads, including French baguettes and sourdoughs, can be considered slow breads because of their longer leavening periods.
Although slow bread takes 18 hours to ferment, mixing the dough is a relatively simple process compared to other types of breadmaking. Flour is mixed with water and the smallest possible amount of yeast to create a sticky dough that is allowed to rest over a long period of time. This resting time allows the yeast to begin fermenting, creating alcohol, acetic acid, and lactic acid that naturally incorporates air into the dough, in much the same way kneading does. The alcohol will burn off in the baking process, giving the bread a more complex taste.
The long period of fermentation is commonly known as leavening. The leavening process allows the starches in the flour to more effectively absorb the water. This technique creates more elastic strands of gluten, the protein that lends this bread its particular chewy texture.
Once the slow bread dough has gone through the leavening process, it is then divided and allowed to rise for another two hours. After it has fully risen, the dough is folded and placed in a heated bread pan or casserole. The dough should be baked at 450 degrees Fahrenheit (232 degrees Celsius) for 30 minutes or until the crust reaches the desired color. The slow bread is then removed from the pan and allowed to cool.
The standardized production of yeast was first developed by Louis Pasteur in 1859. Prior to Pasteur's innovation, slow bread was made with naturally occurring yeasts. At times, these yeasts were simply airborne particles that became incorporated into the dough as it was mixed. Some ancient cultures were known to mix beer and wine into flour or grains to create bread. During the first century, the Roman author and philosopher Pliny the Elder reported the use of "foam skimmed from beer" to create an airier bread.