Which Fruit Has the Most Vitamin C?
Vitamin C (ascorbic acid) is an antioxidant that is essential for human nutrition. Vitamin C
deficiency can lead to a disease called scurvy, which is characterized by abnormalities in the
bones and teeth. Many fruits and vegetables contain vitamin C.
Fruits have varying levels of vitamin C. In some fruits, the amount of vitamin C varies between
different varieties of the same species. The vitamin C content of many fruits is higher when it
is slightly unripe, and declines as the fruit becomes ripe. Vitamin C content also decreases
with storage.
Tincture of iodine is brownish-red in color. When vitamin C is added, it becomes colorless.
This reaction can be used to test for the presence of vitamin C and to give some idea of the
amount that can be found in a given substance.
Problem:
Which fruit has the most vitamin C (ascorbic acid)?
Materials
Fruit or juices from a lemon, apple, grapefruit, kiwifruit, pineapple, pear, and orange
Tincture of iodine
100 mg vitamin C pills
Medicine droppers
500 ml water container
Set 8 oz clear plastic cups
Safety: Tincture of iodine is poisonous and therefore should not be ingested. If iodine gets into eyes, immediately flush with plenty of water. Continue for at
least ten minutes and call for medical help. In case of skin contact, wash off with soap and water. Remove any contaminated clothing. If the skin reddens
or appears damaged, call for medical aid. Do not consume any of the juices and /or fruits connected with this project.
Procedure
1. Prepare an iodine solution by mixing a bottle of tincture of iodine in about 500 ml of water. Place equal amounts of the iodine solution in plastic
cups.
2. Using a spoon, crush a vitamin C tablet and then dissolve it in water (this will be the control).
3. Place equal amounts of the various fruit juices in plastic cups.
4. Using the medicine dropper first add the vitamin C control solution drop by drop to a cup of iodine and record the results. Do not to dip the medicine
dropper into the iodine.
5. Next, add a juice using a different medicine dropper, drop by drop, to a fresh cup of iodine. Swirl the cup after each drop is added.
6. Count the number of drops you add until a color change is seen.
7. Record the number of drops needed to change the iodine from its brownish-red color to a clear or almost clear color.
8. Repeat the procedure using each of the juices.
9. Arrange data in numerical order, from the lowest to highest vitamin C content in a table similar to the one shown below.
10. Test each juice three times and calculate the average number of drops required to change the color.
Name of Juice Number of Drops
Control
Lemon
Apple
Grapefruit
Kiwifruit
Pineapple
Pear
Orange
11. Using the data in the table plot a bar graph of Vitamin C Amount (I 2 drops/Juice) along the Y-axis verses the names of the juices tested along the X-
axis.
12. The data in the table might be further organized as a frequency distribution. The frequency with which each measurement occurs is noted in the
table below, this way the original raw data can be treated graphically. See example below:
Drops per Juice Tally Frequency
40 I 1
35 I 1
30 I 1
20 III 3
15 II 2
12 I 1
10 I 1
13. Plot a statistical histogram graph similar to the graph shown.
Author: Mike Calhoun
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