You and Your Students!
Vicki Cobb, Education World Science Editor
Bring yeast to life, and discover how they ferment.
Yeasts are one-celled plants that are distant cousins of mushrooms. Like mushrooms and other plants that do not contain chlorophyll, yeasts cannot make their own food. They must get their food from their surroundings. When conditions are not favorable, yeasts become inactive; but they will spring to life when conditions are right. The dried yeast sold in packages in the supermarket is ready to show your students an amazing life process called fermentation.
The products of fermentation, alcohol and carbon dioxide, are of utmost importance to the winemaker and the baker. The winemaker is interested in alcohol production, and the baker is interested in the carbon dioxide, for that is the gas that makes bread rise.
This experiment is designed to show your students what type of food yeasts like most (which foods make the most favorable conditions for yeast growth). The experiment can be done in connection with the next experiment in the Show-Biz Science series, which I call Yeast Busters.
This activity can be done as a class demonstration; or students can work in small groups. I prefer the small-group approach because the kids like doing this themselves.
Measure the fermentation activity by the size of the bubbles and how rapidly they form. Students can also sniff the mixture to smell the alcohol.
Glucose, a simple sugar, is the principle "food of yeast use for baking. When yeast comes in contact with glucose, fermentation begins immediately. Glucose is present in corn syrup.
Yeast can also get glucose from table sugar (sucrose) and starch but it takes longer to get going. Sucrose and starch have to be broken down into simpler sugars before fermentation can begin.
The next experiment, Yeast Busters, deals with inhibiting yeast action.
Article By Vicki Cobb
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