Project Name :- Measurement
of the Vitamin C Content in Various Fruit Drinks and Juices :- :-
Abstract
The
purpose of this project was to measure the Vitamin C content of various fruit
drinks and juices. My hypothesis was that if Vitamin C in juice is titrated
with a starch/iodine reagent, then the juice with the largest amount of Vitamin
C will complete the reaction sooner than juices with less Vitamin C. I believed
that the pure Florida juices would contain the highest Vitamin C levels and
would meet the recommended daily allowance (RDA) of 60 mg.
The
juices were titrated into a reagent containing starch and iodine. The amount of
juice needed to complete the reaction was a measure of the Vitamin C content.
The volume of juice titrated was compared to the volume of Vitamin C standard
titrated to calculate the Vitamin C content. I assumed that it was only the
Vitamin C in juice that reacted with the starch/iodine complex. A more
sophisticated method to accurately determine the Vitamin C level would be
necessary to verify the results.
My
hypothesis was correct. The juices containing the most Vitamin C titrated the
starch/iodine reagent with the least volume of juice required. The pure Florida
juices contained the least amount of Vitamin C compared to the other juices
tested. I would recommend the purchase of drinks containing added Vitamin C
such as Welchade Grape.
Materials
----Reagents---
1. 2.5
ml cornstarch
2. 1000
ml distilled water
3. 2.5%
tincture of Iodine (Poisonous if swallowed)
4. 1
250 mg Vitamin C tablet
----Juices Tested---
1. Presidents
Choice Orange Juice
2. Equality
Wildberry McCain Orange Juice
3. Welchade
Grape
4. Equality
Apple
5. Del
Monte Five Fruit
6. Sunny
Delight
7. Master
Choice Grapefruit
8. V8
Splash Tropical Blend
9. V8
Splash Berry Blend
10.
C'Plus Orange
11.
Five Alive
12.
Heinz Tomato Juice
---Equipment---
a)
1 100 ml graduated cylinder
b) 1
500 ml glass measuring cup
c)
2 10 ml plastic syringes
d) 30
250 ml white plastic cups
e)
3 500 ml glass jars with lids
f)
1 medium saucepan
g)
1 small plastic funnel
h) 1
2.5 ml measuring spoon
i)
Hammer
j)
Resealable plastic sandwich bag
Procedure
A. Titration of Vitamin C Standard
1.
25 ml of working starch/iodine reagent was poured into a plastic cup.
2.
4 ml of Vitamin C standard was drawn into a 10 ml syringe.
3.
The standard was titrated into the starch iodine reagent drop by drop. The
number of drops required to change the reagent colour from blue to clear were
counted and recorded. The reagent was gently mixed after the addition of every
few drops of standard.
4.
Steps 1 to 3 were repeated to ensure precision.
B. Titration of Juices
1.
25 ml of starch/iodine reagent was poured into a plastic cup.
2.
4 ml of juice was drawn into a syringe.
3.
The juice was titrated into the starch/iodine reagent. The number of drops
required to change the reagent colour from blue to clear were counted and
recorded. The reagent was gently mixed after the addition of every few drops of
juice.
4.
Steps 1 to 3 were repeated to ensure precision. The difference in the number of
drops counted for the two tests had to be 2 or less or the testing was repeated
a third time.
Conclusions
I
expected that the pure Florida juices, President's Choice Orange and Master
Choice Grapefruit would contain the highest Vitamin C content. This did not
prove to be true. They had the lowest concentration of Vitamin C of the juices
tested and I had to titrate larger volumes of these juices to complete the
reaction.
The
recommended daily allowance of Vitamin C is 60 mg. All products with the
exception of Master Choice Grapefruit met this requirement. Welchade Grape
Juice is an excellent source of Vitamin C, especially for children, since they
would only need to drink 60 ml to meet the RDA.
All
products with the exception of President's Choice Orange and Master Choice
Grapefruit had Vitamin C added. This seems necessary because either there is
not enough Vitamin C in oranges or grapefruits or it is affected by the
processing of the juice. It is known that Vitamin C is lost when it is exposed
to heat or light.
I
would recommend the purchase of juices with added Vitamin C. Vitamin C would be
more stable in juice containers that are protected from light such as juice
packs or cans.
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