The Effect of Natural Ethylene on the Ripening of Bananas Author(s): Dean Papadakis and John Olson Research Question: Can the Ripening Process of Bananas be Speeded Up by Placing the Fruit in the Presence of Already Ripened Fruit? Growth & Development Experiment SED 695B; Fall 2007 Standards addressed: Investigation and Experimentation Here are some un-ripened and ripened bananas. The probe (below) is placed in contact with the banana at an angle to measure the reflectivity of light using the Vernier Light Illumination Probe. 1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will: a. b. c. d. f. g. j. k. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data. Identify and communicate sources of unavoidable experimental error. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions. Formulate explanations by using logic and evidence. Distinguish between hypothesis and theory as scientific terms. Recognize the usefulness and limitations of models and theories as scientific representations of reality. Recognize the issues of statistical variability and the need for controlled tests. Recognize the cumulative Here below is the Light Sensor (photometer) with the LabPro Interface Independent variable Time (Over the Course of Several Days) Dependent variables Controls Series Amount of Color Change from Green to Yellow (measured with a photometer) A single green banana placed in a sealed plastic bag to see how fast it ripens without additional help. Series1 Banana Alone in a Baggie Series 2 Banana with Ripened Bananas Series 3 Banana with Ripened Apples Materials Green Bananas, Yellow Ripened Bananas, Apples, Computer with Vernier LabPro Interface and Vernier Photometer and Plastic Bags Procedures 1. Green, un-ripened bananas and yellow ripened bananas are purchased from the store. 2. The Vernier Light Meter (photometer) is used to see if the difference in color between green and yellow can be measured. 3. Three series of experiments are set up with series one having a sealed plastic baggie with one un-ripened banana inside. 4. Series two has a sealed plastic bag with one un-ripened banana in the presence of three other yellow ripened bananas. 5. Series three has a sealed plastic bag with one un-ripened banana in the presence of three week-old apples. 6. The three un-ripened bananas are measured every two days to measure the progress of the ripening process and to see if there is any difference in the amount of yellow or dark spots between the three sets of bananas. The measurement involves measuring the intensity of the reflected light from the banana skin, in units of LUX. Data Value 1 2 3 4 5 6 7 8 9 Photometer Data Time (seconds) 0.0 0.02 0.04 Etc. Illumination (LUX) The data collected in this table would be collected using a photometer. Here is some illumination data collected for a green un-ripened banana, showing the reflected light from the green skin has a value that is in the high 300’s. Here is the graph of the data shown above, which shows the statistics of the data in the top left corner, indicating an average lux value of 376 and a standard deviation of 17 lux. Here is some illumination data collected for a yellow ripened banana, showing the reflected light from the yellow skin has a value that is in the low 500’s. Here is the graph of the data shown above, which shows the statistics of the data in the top left corner, indicating an average lux value of 506 and a standard deviation of 23 lux. Observations: The two sets of data above, show that using a photometer is a viable way of measuring differences in the color of the skin, through the amount of reflected light from the skin. Principles Involved: It is known that ethylene (C2H2) gas is produced during the ripening process of bananas and fruits. This ethylene gas acts as a hormone to speed up the process of ripening. When bananas are shipped from one country to another, the goal is that the ripening process will be slow. When the bananas reach the supermarkets where they will be purchased, the goal is that the rate of the ripening process will be increased. An ethylene generator can be used for this process. One context where the ripening process should be slow is when NASA wants to send fruit on a mission, and the fruit must be stored for a week or so at a time before a mission. The ripening process should be slowed down as much as possible so that the fruit will be ready for space. References & Links: http://media.nasaexplores.com/lessons/02-042/5-8_1.pdf The website above provides a procedure that middle school students can use to test the ripening of bananas. http://postharvest.ucdavis.edu/datastorefiles/234-726.pdf This powerpoint presentation in the website above shows several images of the ripening process under various conditions.