History of Yeast

Yeast is a single-celled microorganism that is classified in the kingdom Fungi. These microorganisms exist all around us – in soil, on plants and even in the air.

The main purpose of yeast is to serve as a catalyst in the process of fermentation, which is essential in the making of bread.

While there are many types or strains of yeast, at Fleischmann’s® Yeast, our sole focus is on Saccharomyces cerevisiae. This is the yeast that is most commonly used in making bread.

It Started In Egypt

Research shows that ancient Egypt was the home of modern bread. Archaeologists digging in Egyptian ruins found grinding stones and baking chambers, as well as drawings of 4,000-year-old bakeries and breweries.

During this time, bakers were using different grains to create a variety of flavors in their breads. Wheat, which was the most common grain in Egypt, made excellent loaves.

To make their breads tastier, bakers began experimenting with different ingredients. Honey, eggs, dates, seeds and spices were added to provide a welcome and delicious variety of choices.

They would also often make their breads in different animal shapes – like birds, fish and cows. While these breads were meant for everyday consumption, some had special significance for rituals and festivals.

Of course, that tradition continues with certain holiday animal-shaped breads.

Getting a Closer Look

While the art of bread making was evident from ancient times, the science of bread making didn’t develop until 1676, when Anton Van Leeuwenhoek developed the first microscope.

Now scientists could investigate yeast up close and really understand what it was and what it did.

It was Louis Pasteur In 1859 who first discovered how yeast works:

  • Yeast feeds on the starches in flour, producing carbon dioxide
  • The carbon dioxide expands the gluten proteins in the flour
  • The gluten proteins cause the dough (of which flour is a main ingredient) to expand and rise
Nine years after Pasteur’s discovery, Fleischmann’s® Yeast was founded, and the modern baking era was born.


From one tiny yeast cell, tons of yeast can be produced. Here’s how the process works:

  • The first step, using a strong microscope, is selecting one healthy and vigorous yeast cell from the desired strain.
  • Once selected, the cell is planted in a sterile test tube, which contains all the nutrients necessary to make yeast grow.
  • In the tube, the yeast cell reproduces, by budding...or multiplying itself.
  • Once the yeast has multiplied into a small mass of pure cells, it is transferred to glass laboratory flasks.
  • These flasks contain a liquid mixture called wort.
  • Wort is a nutrient-rich growth medium containing molasses or another carbohydrate source, vitamins, minerals and other components.


When the yeast cells have increased many times, the fermentation stage begins.

  • The flasks are emptied into sterilized fermentation tanks. The tanks contain more wort, which causes the yeast to continue to multiply.
  • As the yeast cells continue to grow, they are transferred to increasingly larger tanks.
  • The final tank can be as high as a multi-story building, with a capacity of up to 60,000 gallons.
  • By the time the yeast is ready to be harvested, it will have grown into tons of yeast, multiplying 5–8 times...over 3 generations!


Once fermentation is complete, the yeast is repeatedly washed and then separated from the growth nutrients through centrifugation.

The result is a creamy suspension of pure, active yeast.

From here on in, various manufacturing processes take place, depending on how the yeast is to be used.