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

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Author: Dr. Muriel Gerhard

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

Objective:

The purpose of this project is 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 informational 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 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. In many cases, the acidity of a fruit increases as it ripens, but the higher acidity is not always reflected in its flavor.

Experience has also demonstrated that when most fruits are left outside of the refrigerator, they will begin to brown. The browning is due to the presence of ethylene gas 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 delay the ripening process. Finding methods of minimizing the ripening of produce is of great interest and of practical value. 

This science fair experiment also serves to acquaint students with the essential processes of scientific inquiry such as the importance of using a control, identifying dependent and independent variables, collecting data, depicting data and making good judgments as to the validity and reliability of their findings.

Materials:

  • bananas
  • kiwis
  • apples
  • oranges
  • clementines
  • a bowl
  • a camera

Experimental Procedure:

  1. Gather all the materials you will need for this project. These include bananas, kiwis, apples, oranges, clementines, bowls for each kind of fruit and a camera.
  2. Place each type of fuirt 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. If so, how did you record 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 

Kind of Fruit Browning Ethylene gas odor Moisture Residue Dehydration & Other
Bananas        
Kiwis        
Apples        
Oranges        
Clementines        

                           

                                      Chart#2: Tabulation &Summary of Evidence of Rotting 

Changes Bananas Kiwis Apples Oranges Clementines
Browning          
Ethylene Gas Odor          
Moisture          
Dehydration          
Other          

 

Terms/Concepts:  Ripening, ripening agents, ethylene gas

References:

www.ehow.com/facts_7387865_packaging-affect-ripening-fruit_.html - Cached Burg SP EA (March 1962). “Role of Ethylene in Fruit Ripening”. Plant Physiology.37(2):179-89. Doi;10.1104/pp.37

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