A type of bread known as unleavened bread can be made by mixing flour with water and then baking it. Historically, this is the forerunner of modern bread. Unleavened bread is hard and unattractive to most palates and the resemblance to bread is slight.
Bread is made from flour, water, salt and yeast. It has a honeycomb structure and may be regarded as a solid foam (the disperse phase being has and the continuous phase being solid) with a multitude of pockets of CO2 distributed uniformly throughout its bulk.
Sugars originally present in the flour and that produced by the action of amylase are hydrolysis to glucose which is fermented by zymase in the yeast. Alcohol and CO2 are formed; CO2 aerates the dough while Maoist of the alcohol is driven off during baking. It is estimated that about 7% of the nutrients originally present in the dough are lost as a result of the fermentation process. The small amount of carbonyl is acid produced during fermentation lowers the pH of the dough and this affects the dough.
The CO2, because it lowers the pH also has a beneficial effect on the gluten structure. Some protein break down occurs during the fermentation period owing to the presence of proteolytic enzymes. During this period, the yeast cells multiply and the yeast contributes substantially, together with the fermentation products, to the flavor of the loaf. Two of the proteins present in flour – gliadin and glutenin- become hydrated and form an elastic complex called gluten when flour is kneaded with water.
It is the presence of this elastic gluten that makes the manufacture of bread possible, because it forms an interconnected network which contains CO2 within the loaf and prevents its escape. The gluten is uniformly distributed throughout the dough and the CO2 becomes trapped as small pockets of gas. As has production continues, the gluten strands are stretched and it is thought that bonds between adjacent protein molecules are broken and reformed to produce an elastic gas- retaining three dimensional network.
A ripe dough (one which is ready for baking) is springy, elastic, it can be fairly easily stretched out and shows a capacity to recover its former shape. An under ripe dough is extensible, that is, it can be stretched but lacks elasticity. If fermentation is allowed to continue unhindered, the dough becomes over ripe, and a dough in this condition can not be stretched far without breaking, its power to retain CO2 is lost.