Making bread

There are four main steps in making yeast bread.

Mixing

The first step is to mix the ingredients-flour, water, yeast, and salt-together. During mixing, starch granules absorb water and enzymes digest starch into sugars. The yeast feed on the sugars and produce carbon dioxide and alcohol. Glutenin proteins begin to react into gluten. Mixing can be done by hand, with an electric-mixer, or in a food processor. The later offer the advantage of limited oxygen exposure, which in excess can alter the pigments and flavor of the bread.

Kneading

The second step involves dough development. Through kneading, the dough is stretched, folded over, and compressed over and over. This manipulation strengthens the gluten network. It orients proteins to lay side by side which encourages them to form bonds. Overdevelopment of gluten causes bonds to break and turns the dough sticky and inelastic. Bewrae of overdeveloping the dough when kneading mechanically.

Kneading also aerates the dough. The more air pockets formed, the finer the texture of the final bread. Some breads call for minimal kneading. This results in fewer and larger air cells and their corresponding irregular and coarse texture. The gluten is weak and less developed, but it continues to develop through fermentation and can rise to an airy, tender crumb.

Fermentation (Rising)

The third step is fermentation, where the dough is set aside for yeast cells to produce carbon dioxide. As they do so and the carbon dioxide diffuses into air pockets, the dough rises. Yeast have the highest metabolic activity at 95 degrees F. This produces the greatest amount of carbon dioxide and metabolic by-products, some of which can be sour and unpleasant. For quick rising, it is suggested to keep fermentation at 80 degrees F for a couple of hours. Lower temperatures may extend the fermentation an hour or two, but generally produce more desirable flavors.

The end of fermentation is signaled by the dough's volume and the gluten matrix. Fully fermented dough is about twice its original size and has been stretched to its limit, so a finger impression remains when touched. Fermented doughs feel softer and are easier to handle than freshly kneaded dough.

Fermentation can be retarded by storing dough in the refrigerator. Yeast take 10 times as long to rise bread in cool temperatures. Retarding fermentation not only allows bakers to break up the work of making bread, but it has useful effects too. Long, slow fermentation allows greater flavor development by the yeast and bacteria in the dough. Cold dough handles easier without as much loss of leavening gas. The cycle of cooling and rewarming redistributes gases and promotes the development of a more open and irregular crumb structure.

Baking

The last step is baking. The kind of oven where a bread is baked has an important influence on the qualities of the finished loaf. Traditional bread ovens were made out of clay, stone, or brick. The baker preheated the oven by wood fire to temperatures up to 900 degrees F. The domed roof stored heat and radiated it down onto the loaves. The temperature declines during baking. The dough expands early on. The bread benefits from color and flavor development due to enhanced browning reactions.

Modern metal ovens are not ideal for bread making. The maximum cooking temperature is usually around 500 degrees F. Heat cannot be stored as well within their walls, so modern ovens maintain a heat source of gas or electrical elements. The necessary venting does not allow gas ovens to retain the loaves' steam. Some bakers use ceramic baking stones or ceramic oven inserts that mimic the traditional oven. The oven is preheated to its maximum temperature and provide more intensive even heat during baking.

Steam is important in the early baking stages because it increases the rate of heat transfer from the oven to the dough. As steam condenses onto the dough surface, it forms a thin film of water that temporarily prevents it from drying out into a crust. By doing so, it encourages the initial rapid expansion of the loaf. The hot water film eventually dries into an attractive glossy crust. Professional bakers often inject steam in the first minutes of baking. At home, one can spray water or throw ice cubes into the hot chamber to improve oven spring and crust gloss.

There are three stages of baking plus cooling.

Early baking: Oven Spring refers to the first 6-8 minutes of baking. Heat transfers first from the oven floor to the bottom of the dough, and to the top from the hot air and oven ceiling. Heat moves from the surface through the dough slowly through the gluten matrix; and rapidly through the gas network.  Alcohol and water in the dough vaporize. The gas cells expand, and the dough rises. The better leavened the dough, the faster it cooks.

Mid-baking: The dough begins to transform into a sponge when the interior temperature of the dough reaches 155-180 degrees F/68-80 degrees C. At this range, the gluten proteins form strong cross-link bonds, the starch granules gelate, and the amylose molecules leak out. Gas pressure builds and ruptures the walls, turning the closed network of bubbles into an open network of pores similar to a sponge.

Late baking: Starch continues to gelate thoroughly. Continued cooking encourages surface browning reactions that improve color and flavor. Though limited to the crust, these reactions affecte the flavor of the whole loaf because their products diffuse downward. Bread is done when its crust has browned and the inner structure has set. Fully cooked bread feels light and hollow.

Cooling

The temperature varies inside a loaf immediately after being removed from the oven. During cooling, the differences even out.  Most moisture loss occurs at this stage as moisture in the interior diffuses outward. Small rolls dry out the most, while large loaves the least. As temperature declines, starch granules become firmer, which later allows even slicing. This firming continues over the next day and starts the process of staling.