Bread: Leavening

The third essential for a risen loaf was a gas-forming agent or leaven. The discovery of this has been credited to the Egyptians. It was probably by accident when a batch of dough became infected by the wild yeast spores which float in the air everywhere. If, for reasons of economy, the apparently spoilt, rotten dough was baked anyway, it would have been realized that the bread was lighter and had a special, good flavour. Later came the discovery that a piece of leavened dough could be kept to spread the infection to the next batch. Egyptian leavened and unleavened bread of various shapes and sizes has been found, preserved by the dry desert sand. An inscription of the 20th dynasty lists 30 different kinds of bread. From 2000 BC or earlier there were professional bakers.