|MadSci Network: Microbiology|
Food is typically analyzed for microorganisms (bacteria, yeast & molds) by preparing an aqueous homogenate and then placing a portion of that homogenate (or dilution) of that homogenate into microbiological growth medium. The agar plates are then incubated at various times and the subsequent colonies are counted. This is a quantitative determination and can sometimes be qualitative by adding selective agents to the agar growth medium. In your specific experiment, you need to measure by observation the difference between food which has fallen onto the floor and food that has not. One fact that must be kept in mind is that the over riding variable in this experiment will be the microbiological quality of both the food and the floor. If the food has many microorganisms in it naturally then dropping it on a floor with less microorganism will not add or remove organisms. I would suggest dropping a food with no microorganisms such as a freshly popped pop corn (which has cooled to room temperature). I would suggest a less than clean (moist if possible) floor. After dropping a few pop corn pieces on the floor for different time intervals place them on the agar surface. DO not forget to include on which did not drop oin the floor (as a control). Dispose of the agar plates (appropriately) after incubating for 1-5 days at room temperature.
Try the links in the MadSci Library for more information on Microbiology.