Astonishing Apples! What Preserves Apples Best?

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Updated on Mar 17, 2010

Type

Chemistry

Grade

Middle School

Difficulty of Project

Easy

Cost

$ 10 -$15

Safety Issues

Wear safety glasses, apron and plastic gloves.

Material Availability

Readily available from super market and from Chem. Scientific.

Approximate Time Required to Complete the Project

2 weeks. This includes collection, recording and analysis of data, summary of results and completion of bibliography.

To determine which of the following substances best preserves an apple: lemon juice, lemon juice plus ice, citric acid, sugar syrup, pure ascorbic acid?

3lbs of apples, lemon juice, citric acid, salt, sugar syrup, pure ascorbic acid powder, water, paring knife, zip-lock freezer bags, stirrers, 4 bowls, and 7 pint sized containers.

On the information level, this experiment serves to acquaint students with current data on the chemistry of preserving light colored fruit such as apples, pears and peaches. Students learn that enzymes in these fruits cause this oxidative browning when these fruits are peeled or cut. In addition they learn that the browning can cause loss of vitamin C. To prevent this browning and this enzyme interaction, a variety of substances are used with differing results. What the student comes away with is an understanding of some of the ways we use the science of chemistry to preserve and thereby protect our food supply.

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.

  • enzymes
  • browning
  • oxidation
  • preservation
  • vitamin c
  • ascorbic acid

  • Whatcauses the browning of apples and pears when they are peeled and cut?
  • How do enzymes affect oxidation?
  • What are some of the methods used to preserve these fruits?

  • What is a control? A control is the variable that is not changed in the experiment.
  • What purpose does a control serve? It is used to make comparisons as to what changed or possibly caused the change.
  • What are variables? Variables are factors that can be changed in an experiment.>
  • What is an independent variable? The independent variable is the one that is changed in the experiment.
  • What is a dependent variable? The dependent variable is the one that changes as a result of the change in the independent variable.

Samples
Observations
Lemon Juice

Lemon Juice plus Ice

Citric Acid

Sugar Syrup

Ascorbic Acid

Control

  1. State the problem you are going to investigate.
  2. Create and reproduce the data sheet you will use to record your observations.
  3. Gather all your materials.
  4. Put on your safety glasses, plastic gloves and apron.
  5. Gather all your materials.
  6. First, wash, peel, core and cut the 3 lbs of apples into pieces of almost the same size.
  7. Prepare a solution of lemon juice by combining 2 tbsp of lemon juice with 2 quarts of water.
  8. Prepare the syrup by dissolving 2 ½ cups of sugar in 4 cups of warm water and stir well.
  9. Prepare the ascorbic acid by adding ½ teaspoon of the acid to 4 cups of water.
  10. Prepare the citric acid by adding 2 tbsp of the acid to 2 qt. of water.
  11. Label each of the pintsized containers as well as one control.
  12. Place an equal amount of apple slices in each of the labeled containers and the add the proper solution to each container based on the label. For your test with lemon juice and ice, just add two ice cubes to your container. Be sure to cover the apples thoroughly with the proper solution. Let them stand for one hour. Then remove the apple slices and place them in individual freezer bags. Label each bag. Record your observations. Analyze your data and record your conclusion.
  13. Prepare your report and include all of the following: a clear statement of the problem, your hypothesis, namely what did you predict would occur, and a list of the materials used. Include the safety precautions taken. Describe the procedures used. Include all the data that were gathered. Include the chart. Explain the purpose of the control. Formulate your conclusions. For dramatic value, you may include photos of the materials used or of you in the process of conducting this investigation. Include a bibliography of sources you used. You may wish to assess what you did and describe what you would do differently if you were to do this project again. You may wish to expand this research next year. What other materials might you investigate for this purpose? Are there other combinations of substances that could be safely tried?

Drusilla Banks: So easy to Preserve, Fourth Edition, and University of Georgia Cooperative Extension Service

Linda Marie: How to Freeze Apples Using Lemon Juice, University of Illinois Extension

Dr. Muriel Gerhard (Ed.D.) is a retired educator with fifty seven years of experience in all aspects of public education. She has been a teacher, principal, administrator, college professor, researcher, grants writer, change agent and science editor. She is the author of several books on education used as college texts. These include the best selling Effective Teaching Strategies with the Behavioral Outcomes Approach and The Behavioral Outcomes Handbook for Teachers and Administrators. Presently she is a consultant in science education and curriculum development, a marriage and family therapist, a newspaper columnist and an author. Her latest book, recently published, is a memoir of sixty vignettes entitled ΓΆNow That I`m Dead, I Decided to Write this Book.ΓΆ

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