Yeast is a single-celled organism classified in the fungi group. When fungi grow with sugar as their source, carbon dioxide bubbles are produced. Demonstrate the bubbling action created from fungi growing on the sugar in apples. Warm 1 cup of water in a beaker. Add 1/4 cup of apple juice and 2 teaspoons of baker's yeast. Have pupils measure and record the carbon dioxide bubbles produced from the fungi reacting with the sugar in the apple's juice. Conduct the experiment with various sugar sources and compare the reactions.
Fungi do not contain chlorophyll and therefore must take their food from other sources. Allow pupils to watch fungi grow on an apple as their source of sugar. Cut two slices of an apple. Place each slice in a separate zip-lock bag. Label one bag the control and close the bag. Place 1/2 teaspoon of baker's yeast with the apple slice in the second bag. Label the bag as containing fungus and close the bag. Pupils should observe the fungal growth on the apple after 48 hours and record their observations.
A sealed crisper drawer in a refrigerator will help keep apples fresh longer. Apples need lower humidity levels than that of the rest of the refrigerator. Observe and record the reaction of fungi growing on apples in various locations. Peel and crush three apples. Divide and scoop the crushed apple material into three bowls. Add 1 tsp. of baker's yeast to each bowl. Place one bowl at room temperature, one on the refrigerator shelf and one bowl in the fruit crisper drawer. Compare and record the fungal growth after 48 hours.
Mold is a type of fungus. Compare the growth of mold on different apple varieties. Choose four apple varieties, such as Honey Crisp, Macintosh, Red Delicious and Golden Delicious. Slice the four apples. Place each apple variety in a separate, sealed zip-lock bag. Set the bags at room temperature. Observe and record the mold growth on the apple varieties after 48 hours.