Fermentation is the metabolic breakdown of biological chemicals. The process is used to make bread, liquor, beer and wine, as well as ethanol fuel. Yeast, a type of fungus, causes fermentation of the raw materials necessary to produce these things. When discussing fermentation with grade schoolers, explaining the process of fungal fermentation using yeast can be centered around experiments with rising dough.
Considering Grade Level
The age and grade level of the children you speak to must be considered when explaining fungi fermentation. Parents may be quite sensitive to any scientific discussion that references alcoholic beverages to students in the lower grades. Focus instead on the effects of fermentation in making bread rise or generating fuel for vehicles.
Discuss Types of Fungi
Explain to students that fungi are organisms that decompose organic matter. Give examples that students may have seen in their daily lives, such as a mushroom growing on animal excrement or lichens on trees. Show the students different types of fungi, such as mushrooms, lichens, moss and yeast. If you show dried yeast, explain that fermentation is what happens when yeast consumes organic matter and releases carbon dioxide.
Carbon Dioxide Experiment
Carbon dioxide is released as part of the fermentation process. Gather flasks, rubber stoppers with holes in the center, plastic straws, sugar, water, limes and yeast packets. If you can, provide enough for all students to be grouped in pairs with two flasks per pair. Direct students to pour half a cup of water into both flasks. Pour a teaspoon of sugar into one of the flasks. Add a packet of yeast into the flask. Plug the flask with the sugar with the rubber stopper. Insert one end of a straw into the hole of the rubber stopper. Squeeze half of a lime into the other flask. Insert the free end of the straw into the flask with the lime. Ensure that the straw is submerged into the lime water. Watch as the lime water becomes cloudy from the carbon dioxide.
Express that the carbon dioxide produced by the yeast's digestion of sugar in the water causes dough to rise when yeast breaks down sugars present in grain. Give student groups a small ball of dough without yeast. Ask students to add a small amount of yeast from their packet onto their dough and to knead the dough for a few minutes. Then students must set their dough to the side. Check how large the dough has expanded before leaving school for the day. Check the size of the dough the next morning. Explain that the fermenting of grain and sugars in the dough adds to the different textures of different types of breads.
- Wageningen University: Fermentation and Fungi
- Fungus; Fungal Biotechnology; Paul F Hamlyn
- University of Sydney; Fungal Biology; Fermentation
- Applied Environmental Biology; Growth and Fermentation of an Anaerobic Rumen Fungus on Various Carbon Sources and Effect of Temperature on Development; Susan E. Lowe et Al
- University of Missouri-St. Louis; Bubbly Yeast; Theresa Thiel
- Delta Education; Fungi-Small Wonders; Grades 5 - 6
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