Kneading dough may seem like a common kitchen routine, but there is actually some complex chemistry behind bread making. A chemical reaction with the yeast occurs in the dough, turning it into delicious bread. Here is the chemistry of bread making:
- Yeast: The rising of the dough. To produce a bread that is light and easy to chew, gas bubbles must be incorporated into the dough. This process is known as leavening. Most bread recipes call for stirring yeast in warm water until it dissolves. Yeast feeds on the sugar in the bread dough, creating CO2 and ethanol through a process known as fermentation. The yeast ferments the sugar best at a temperature of around 32 degrees Celsius. As the yeast mixture is incorporated into the dough, the CO2 forms gas bubbles, making a light and airy bread. Ethanol contributes to the flavor of the bread.
- Kneading bread to create gluten. The yeast is now kneaded with flour and other ingredients. In the bread dough, there are proteins created by the mixing of flour with water. These proteins, glutenin and Gliadin, become more elastic as they form bonds with water and with each other. Kneading strengthens these bonds. The resulting mass of molecules created by these proteins is known as gluten. If the bread is not kneaded enough before baking, the end result will be crumbly because of weak gluten bonds. Over-kneaded dough, on the other hand, is chewy because the gluten bonds are very strong.
- Letting the dough rest. Most bread recipes call for letting the bread rest before shaping it and baking it. Giving the dough time to rest lets the gluten bonds relax, making it easier to shape the dough into a loaf, into rolls, or into any other shape. Letting the dough rest also allows the dough to rise. This happens because the yeast is still reacting with the sugar to produce CO2. The strong gluten bonds trap the CO2 in the dough, in the form of small bubbles.
- Punching the dough down. Once the dough has rested, most bread recipes call for punching it down. This releases the larger CO2 bubbles. If you do not let these gases escape, the bread may take on a yeasty flavor.
- Shape the dough and let it rest. Once the dough is shaped into the desired form, let it rest a few minutes before baking. This ensures that the yeast reaction is complete; the yeast will stop working in the heat of the oven, because yeast cells die at high temperatures.
Although bread is one of the earliest forms of prepared food, the chemistry of bread making is actually quite complex. In the ancient days, bakers were held in the highest respect because of their talents in managing and understanding the process of making bread.