Where does yeast come from

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Yeast is a universal baking ingredient with a fascinating ancient history

Yeast is a universal baking ingredient with a fascinating ancient history

If you have ever baked a loaf of bread, or experimented with brewing beer or wine, it is likely that you have used yeast as an ingredient.  If so you may have wondered why it was so important to include this seemingly trivial component in your recipe.  Perhaps you even wondered, where does yeast come from?

The easy answer to that question is the fact that common yeast varieties such as baker?s yeast are widely available in grocery stores.  However, this familiar product has an intriguing and unusual history with ancient origins.
Egyptian hieroglyphics offer some of the earliest proof that yeast was used as a baking and brewing ingredient over 5,000 years ago.  Grinding stones, baking ovens for yeasted bread, and sealed urns containing cooking and brewing ingredients have also been discovered amidst ancient Egyptian ruins.

The Bible also makes reference to leaven, a soft, doughy type of bread.  Yeasts left over from brewing or wine making were used as starter cultures for these biblical leaven recipes. 

Where does yeast come from?  While the earliest uses of yeast can be traced to ancient Egypt, Greece, Rome, Middle Easter and even primitive European cultures, yeast is certainly not native to any of these places. 


The fact of the matter is, nearly 2,000 unique species of yeast can be found universally occurring across the globe, in the air, and in the soil; where ever there exists natural plant matter.  

Yeast is actually a tiny microorganism, classified in the plant kingdom of Fungi.  Where does yeast come from?  In essence, yeast could be considered a mushroom or mold variety that feeds on the natural sugars found in grains, fruits and vegetables; producing carbon dioxide as a byproduct of its consumption.

Yeast has been around for so long, it has come to be recognized as ?the oldest plant cultivated by humans.?

The earliest human cultures identified yeast as a leavener, a catalyst in process that caused bread to rise and juices to ferment.  These primitive cultures could not identify where yeast came from, or how, or why it worked.  They simply accepted that the occurrence of yeast was a mysterious, magical, spontaneous natural process.

It wasn?t until 1859 that Louis Pasteur, a French chemist and microbiologist sought out a superior answer to the question; where does yeast come from.  Pasteur discovered that yeast was actually a living, single cell organism, able to actively grow and reproduce.  He identified that fermentation was actually a form of cellular respiration carried out by yeast cells.  This ground breaking discovery forever negated the idea of spontaneous generation, and led to drastic improvements in food preservation and sterilization.

Today, a variety of yeast called Saccharomyces cerevisiae is commonly used as baker’s yeast, while a yeast species known as Saccharomyces carlsbergensis is used to produce a majority of beers and lagers, and yeasts such as Saccharomyces Banyus or Saccharomyces Fermentati are used in wine making.

The next time you bite into a sandwich, take a moment to observe the tiny air bubbles that give the bread its spongy texture.  These bubbles were created by active yeast, which caused carbon dioxide to rise through the baking bread.  It may surprise you to think that the very yeast cultures that gave rise to your lunch sandwich could be thousands of years older than you.