The Story of Yeast
Yeast in History
Yeast can be considered man's oldest industrial microorganism. It's likely that man used yeast before the development of a written language. Hieroglyphics suggest that the ancient Egyptian civilizations were using yeast and the process of fermentation to produce alcoholic beverages and to leaven bread over 5,000 years ago. The biochemical process of fermentation that is responsible for these actions was not understood and undoubtably looked upon by early man as a mysterious and even magical phenomenon.
Leaven, mentioned in the Bible, was a soft, dough-type medium kept from one bread baking session to another. A small portion of this dough was used to start or leaven each new lot of bread dough.
It is believed that since early times, leavening mixtures for bread making were formed by natural contaminants in flour such as wild yeast and lactobacilli, organisms also present in milk.
It was not until the invention of the microscope, followed by the pioneering scientific work of Louis Pasteur in the late 1860's, that yeast was identified as a living organism and the agent responsible for alcoholic fermentation and dough leavening. Shortly following these discoveries, it became possible to isolate yeast in pure culture form. With the newfound knowledge that yeast was a living organism and the ability to isolate yeast strains in pure culture form, the stage was set for commercial production of baker's yeast that began around the turn of the 20th century.