Rotting Fruit! Which Fruits Rot the Fastest, the Slowest? How do We Explain the Differences?

Grade Level: 7th - 8th; Type: Chemsitry

Objective:

The purpose of this project was to determine which of the following fruits, bananas, kiwis, apples, oranges or Clementine’s rot the fastest?

Research Questions:

• How is ripening defined? 
• What are some of the common methods of delaying ripening? 
• What are some of the substances commonly used as ripening indicators/ 
• What are the properties of ethylene gas and at what concentration is this gas dangerous? 
• What steps can we take to prevent fruit from rotting? 
• When is refrigeration useful and when should it be avoided in regard to preserving fruit?

On the information level, this experiment serves to acquaint students with basic information on the ripening process in fruits. When fruits become overly ripe, we classify them as having become rotten. Our experience has shown us ripening is a process in fruits that causes them to become more palatable. None of us enjoy eating unripe fruit. Fruits become sweeter, less green and softer as they ripen. Although in many cases, the acidity of the fruit increases as it ripens, the higher acidity is not always reflected in its flavor. Experience has demonstrated that when most fruits are left outside of the refrigerator, they will begin to brown. The browning is due to the presence of gas, ethylene found in the air. The fruits themselves are producers of ethylene which is a ripening agent. Fruits will remain fresh and firm until the concentration of ethylene surrounding them becomes high enough to stimulate further ripening. Many fruits are shipped when they are not fully ripe and then sprayed with ethylene gas on arrival. On the market today we find specially treated bags and packaging materials that are designed to prevent the exchange of ethylene gas and detain the ripening process. Finding methods of minimizing the ripening of ripe produce is of great interest and of practical value. 

This science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and or graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings. They take on the role of scientists and in the process they learn to act as one.

Materials:

• bananas
• kiwis
• apples
• oranges
• Clementine’s
• a bowl
• a camera

Experimental Procedure:

1. Gather all the material you will need for this project. These include bananas, kiwis, apples, oranges, Clementine’s, bowls for each kind of fruit and a camera.
2. Place all of the fruits, each in a separate bowl where they will not be handled. Keep them at room temperature.
3. Copy and reproduce the Daily Observation Chart making sufficient copies so that you can readily record your daily observations. Make one copy of the Summary Chart.
4. Take photos of the before, during and after stages of this experiment.
5. Observe each of the fruit samples on a daily basis for a period of 14 days, recording any changes in appearance, any odors, any browning of the skin, and any residue of moisture any signs of dehydration.
6.  Note if you were able to detect the presence of ethylene gas and if so record how you did this.
7. Review all of your data. Write your final report. Include your photos, charts of data, a summary of your research and your bibliography.

                                                                           Chart #1: Daily Observations of Changes