How Much Vitamin C?
I. INTRODUCTION: Vitamin C is found
in many fruits and vegetables. Since the body has a limited ability to
store Vitamin C, it is important that humans ingest it frequently. Vitamin
C is important for maintaining collagen, a protein necessary in the growth
and formation of bones, skin, and ligaments. It also helps in the fighting
of bacterial infections, preventing hemorraging, and growing red blood
cells. This activity will investigate the amount of Vitamin C in various
juices.
II. MATERIALS: Vitamin C indicator, medicine cups or baby food jars
(24 well titer plates may be used with microchemistry), droppers (beral
pipettes), freshly squeezed orange juice, bottled orange juice, frozen
orange juice concentrate mixed according to directions. Other possible
sources of Vitamin C may be used including a Vitamin C tablet powdered
and dissolved in water.
III. PROCEDURES: Record your data in the chart below.
- type of juice trial 1 trial 2 trial 3 average
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
- 7.
- 8.
- a.Place 10 mL of the indicator into each cup
or well of the titer plate for each source of Vitamin C that you plan to
check.
- b. Using the medicine dropper (or beral pipette)
add a drop of the orange juice sample and swirl the cup. Instead of swirling,
you may use a glass stirring rod or wooden splint to stir the sample.
- c. Continue to add drops of juice, swirling or
stirring after each drop, until you observe that the indicator has become
colorless.
- d. Observe, count, and record the number of drops
in data chart.
- e. Repeat the steps with each sample being tested.
Test each juice three times and get the average number of drops needed
to change the indicator. If pressed for time, one trial may be all that
is possible.
- f. Don't forget to clean the titer plates so
they may be used by the next class.
- IV. INTERPRETING THE RESULTS: Convert
the data into a bar graph comparing the juices tested. Which type of juice
had more Vitamin C? Why do you think so?
-
- V. ADDITIONAL ACTIVITIES:
- a. Compare a variety of fruit juices to see which
has the most Vitamin C.
- b. Do a cost analysis to determine which juice
has the most juice for the money.
- c. Compare Vitamin C tablets to Vitamin C of
fresh and frozen fruit juices.
- d. Compare Vitamin C content of fresh vegetables
with the content of cooked vegetables or determine how much Vitamin C is
lost in the water that vegetables are cooked in. An additional Activity
might be to measure the effect of baking soda on Vitamin C content when
it is added to the cooking water of vegetables.
- Source: Beisenherz,
Paul and Stephen Blume. "Have You Had Your OJ Today?" Science
Scope, Vol. 12, No. 2. October 1988, pp. 14- 17.
- Note: Preparation
of the Indicator:
- Dissolve 1 gram of cornstarch in 100 mL of cold,
distilled, water. Bring the solution to a full boil in a glass beaker or
porcelain pan. To 1 liter or water, add 8 mL of the cornstarch solution
and 1 mL of tincture of iodine (NOTE: POISONOUS). The color of the
indicator should be a royal blue.
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