Dough chemistry

The simple science behind one of the world’s oldest recipes

Humans have been baking bread for a long time, with some scholars suggesting it existed in a primitive fashion at least 30,000 years ago. By the time of the ancient Egyptians bread was not much different than it is today. Both the basic ingredients of flour, yeast, water and salt, and the process of kneading, rising and baking, have remained largely unchanged for thousands of years.

The molecular star of this staple food item is a protein complex called gluten. After grains such as wheat, rye or barley are milled into a flour they retain groups of proteins called glutenins and gliadins. When water is added to the flour, these proteins are able to mix and form multiple types of bonds, including disulphide bonds. Gluten is the product of this cross-linking process between glutenins and gliadins, and its special properties create a light, fluffy loaf.

In dough, gluten forms a lattice of interlinked strings of protein, making it both strong and flexible. The result (when the dough is well mixed) is a viscoelastic structure. This describes a material that is strong enough to resist some force but also elastic enough to return to its original dimensions once it has been stretched. This attribute is key to permitting bubbles of gas to form and expand within the dough, as the gluten lattice will readily move aside for expanding bubbles but won’t collapse while doing so. This means that plenty of gas can be stored and during baking will expand, producing a large, light loaf of delicious bread.