A few science fair project ideas using bananas include measuring which food grows mold fastest, measuring how sugar content changes in ripening bananas, and determining how air affects the ripening of bananas. Each project requires several days to complete.
For a food mold-growth project, the student places a banana, a slice of bread, a slice of cheese and several other perishable food pieces in a non-refrigerated cabinet. He may then make hypotheses about which fruit becomes moldy first and which one lasts longest, checking on the samples after four to five days. The student takes photos of the food before and after the experiment, documents the results, and theorizes about why certain foods spoil.
For a sugar content experiment, the student gathers several bananas ranging from green to very ripe. Using a refractometer, the student measures and documents the sugar content of each banana over a period of six to 10 days.
To complete a banana ripening experiment, the student places bananas of equal ripeness in different types of packaging, such as a paper bag, a plastic bag, a sealed plastic container and a cardboard box. The student then photographs and notes the results. Students can complete similar science projects measuring how light, humidity and any other factors affect the ripening process.