Yeast  Yeast is a single-celled fungus that is  used in the preparation of food and drink.  There are hundreds of species, but two are the most useful.  They are Saccharomyces and Candida.  These single cells are tiny, but they have a huge appetite feeding on carbohydrates.  They take in air and give off carbon dioxide.   It is the pressure of this gas which makes bread rise.  When they have little access to air, as in a fermentation chamber for brewing beer, the yeast cells concentrate on turning sugar into alcohol. The same species of yeast Saccharomyces cerevisiae is what we refer to as both brewer's and baker's yeast.  Throughout history, bread and beer have been produced together. Elizabeth David, English food writer, described the miracle of yeast: "In Chaucer's England one of the names for yeast or barm was goddisgoode 'because it cometh of the grete grace of God.'  These words imply a blessing.  To me that is just what it is.  It is also mysterious, magical.  No matter how familiar its action may become nor how successful the attempts to explain it in terms of chemistry and to manufacture it by the ton, yeast still to a certain extent retains its mystery." Our exhibit on yeast includes the following:    A short video of yeast in action. A history of the science of yeast.   Adding yeast to  pizza dough.   The Science Of Yeast     This is just one part of an informative and attractive website offered by Fleishmann's Yeast.  Here is the link: http://www.breadworld.com/sciencehistory/science.asp Yeast is a tiny plant-like microorganism that exists all around us - in soil, on plants and even in the air. It has existed for so long, it is referred to as ‘the oldest plant cultivated by man’. 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, our sole focus is on Saccharomyces cerevisiae. This is the yeast that is most commonly used in making bread. 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, as certain holidays are associated with particular types of bread. While the art of breadmaking was evident from the beginning, the science of breadmaking didn’t develop until 1676, when Anton Leewenhoek 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. THE PRODUCTION OF YEAST 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. FERMENTATION 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! SEPARATION 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 Pizza Dough : Mixing and Adding Yeast Step 2: Stir together the water and yeast in a measuring cup, and set aside to allow the yeast to activate. You'll see frothy bubbles forming on the surface. Step 3: Combine the flour and salt in the bowl of a food processor… …and pulse briefly to mix. Step 4: With the motor of the food processor running, gradually pour in the yeast/water mixture… …until a dough forms, about 20 seconds. Step 5: Again with the mixer running, add the olive oil in a thin stream until just incorporated throughout the dough. Step 6: Turn the dough out into a lightly oiled bowl… ...then flip it over to coat. Cover the bowl with plastic wrap and set in a warm place. Let rise 45 minutes while the oven comes up to full temperature, 500 degrees F.