Thanksgiving Week Science: Yeast and Making Bread

We do a lot of baking at our house, and many of our favorites use yeast as a leavening agent. Yeast is a member of the fungi family, cousins to mushrooms, molds and mildew. Yeast must have three things in order to grow -moisture, food, and warmth. Once they have these three conditions, they reproduce, which is called budding.

"When a yeast buds, the nucleus of the cell reproduces inside a single cell. A section of the cell wall and plasma membrane then swell to form a pouch...This pouch is called a bud. The bud continues to grow until it is about the same size as the parent cell and then the two cells seperate." -Exploring Creation with Biology, Wile ("Experiment" 4.2)

The yeast begins to feast on the sugars, breaking them down into alcohol and carbon dioxide. The carbon dioxide pushes its way out of the dough, causing the dough to rise. When the dough is put into the oven, the yeast are killed and the alcohol evaporates.

Since one of the products of fermentation is alcohol, yeasts are also used to put the alcohol into alcoholic beverages.

Mix one packet of yeast with one cup of warm water in a glass. Add one tablespoon of sugar or honey. Stir gently. Let the mixture stand for five to ten minutes. As the mixture stands, you should be able to see bubbles forming -in fact a whole layer of foam caused by the bubbles will form and grow as time goes on.
If you have a microscope, ou could place a drop of he yeast solution on a slide (and coverslip) and observe the budding process. You might even see chains of budding yeast.

If you wish, you can now use your yeast to make bread, rolls or pizza dough.