History of yeast

The history of yeast dates further back than written language. Egyptian hieroglyphics, dating back 5,000 years, depic the Ancient using yeast  for alcohol fermentation as well as a leavening agent. It is believed that early fermentation occurred naturally through contamination of fruit and flour. The Ancient used yeast even though they did not understand it. The faculties of yeast were often attributed to magic.

Leaven, as it is described in the Bible, was a soft dough-like medium. A small portion was reserved as a starter dough for new bread. By saving "good" batches, man naturally selected the best yeast for his baking/fermentation needs. Yeast is therefore considered the first industrial microorganism.

Yeast was not identified as the living organism responsible for fermentation and leavening until after the invention of the microscope in the 1600s and the work of Louis Pasteur in the 1860s. Isolation of pure cultures gave way to commercial production and manufacturing starting at the turn of the 20th century.