EXPANDING YEAST
"Lester, yeast is a fungus, a family of organisms that includes mushrooms, molds, and the little critters that give you athlete's foot. You're familiar with them?"
"I am home to many and considered a fun guy by fungi."
"Remember, yeast is a living thing and living things have to eat. When we got the yeast wet, we woke it up and it started eating the sugar in the water. And when things eat, they give off waste products. This process is called fermentation."
"When the yeast eats the sugar it gives off two waste products, alcohol and carbon dioxide gas. The carbon dioxide gas is what makes the dough rise. As bread bakes, the alcohol evaporates and the yeast becomes deceased. But the gas bubbles stay in the bread giving it a light, airy texture. Look closely at a slice of bread and you'll see all the holes where the bada-bubbles used to be!"
An individual yeast organism is a single-cell fungus that can only be seen with the aid of a microscope. When conditions are right (warm and moist with available food) yeast cells multiply rapidly by a process called budding. This simply involves forming a little bud which grows to become a new yeast cell that breaks away from the parent cell. Besides yeast, most other organisms -- even YOU -- give off carbon dioxide as a waste product.
Ancient Egyptians probably discovered the process of bread rising. Airborne wild yeasts accidentally got into their bread dough, causing it to expand. The classic sourdough bread made famous by California gold miners also used a mixture of wild yeast!
The word "fungus" makes most people think, "yuck!" While it is true that fungi cause food spoilage, plant diseases, rot and decay, they are useful to us not only in baking bread, but in the manufacture of cheese, alcohol, and antibiotics, too.