Analyze the patterns of mold growth under varying conditions. The conclusions drawn from this experiment can help students understand how to store bread and make it last longer. Use the following suggestions to test variables that contribute to mold growth.
Air circulation: Place one slice of bread out in the open air, and wrap the other slice in plastic wrap.
Light: Place two slices of bread in separate plastic bags. Put one plastic bag in a sunny or bright location, and place the other slice in the same location but inside in a paper bag.
Moisture level: Place two slices of bread in separate plastic bags. Add a small amount of water to one of the bags. Add water daily to the wet sample daily to maintain proper moisture levels.
Temperature: Place two slices of bread in separate plastic bags. Put one plastic bag in a dark, warm area such as a cabinet or pantry. Place the other bag in the refrigerator.
Observe each slice of bread daily and record any changes in the bread or appearance of mold.
Identify common types of bread mold. To begin the experiment, sprinkle a slice of bread with approximately 1 tsp. of water, and place the bread in a sealed plastic bag. Observe the bread daily for mold, and record any differences in the color or types of mold. Rhizopus is the most common bread mold and grows a fuzzy, black colony. Greenish-bluish molds with a white powdery border are from the genus Penicillium. This mold is the basis for the antibiotic penicillin. Aspergillus, similar in appearance to Penicillium, grows in a greenish-bluish colony without a white border.
Sourdough bread has much higher acid levels than other types of bread. Demonstrate the effects that acid levels have on mold growth. Begin by placing similar-sized pieces of each bread type in a plastic bag. Add a few drops of water to each bag. Observe the bread daily and record mold growth. The white bread should grow mold much faster, as the acidic environment of the sourdough bread is not conducive to mold growth.
Most bread purchased in the supermarket have added preservatives to inhibit mold growth. Show how preservatives can significantly extend the shelf life of bread and other products. Place a slice of regular packaged white bread in a plastic bag with a few drops of water. Place a slice of homemade white bread or other preservative-free bread in a second bag, and add a few drops of water. Observe the bread daily, and notice how quickly the mold begins to grow on the preservative-free slice.