The amount of vitamin C in grapefruit juice and apple juice - Pieter

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					      The amount of vitamin C in grapefruit juice and apple juice
                                 Engels, L., & Nicolai, A.
                      Gymnasium Haganum Den Haag, The Netherlands

                                    Received march 2009

Vitamin C can be found in a lot of fruits. It’s very important for a human being to get
enough vitamin C in the body, if you don’t get enough vitamin C in you body per day;
you are risking deceases like scurvy. In contrast to a lot of animals, human beings
cannot make there own amount of vitamin C in their body.
The question of this experiment is in which juice the biggest amount of vitamin C is
concentrated. The hypothesis is that the amount of vitamin C is bigger in grapefruit
juice than in apple juice.

Vitamin C, or ascorbic acid, is a very           The amount of vitamin C is findable
important vitamin for a human being.             when it’s titrated with a solution of KIO3
A deficiency in vitamin C causes                 If you add a bit of starch and sulphuric
scurvy, a notorious decease for sailors          acid the mixture will turn in to a
during long routes, which used to afflict        black/blue solution. The question
the V.O.C. during the 17th century.              arises which mixture (apple juice or
Vitamin C is essential for a good                grapefruit juice) will turn into a
resistance, and helps to build bones,            blue/black solution first. Therefore is
teeth and veins. Vitamin C is also an            the question for the experiment:
antioxidant, and protects the body               Which juice contains the biggest
against the reaction between other               amount of vitamin C, grapefruit juice or
matter and free radicals in oxygen,              apple juice?
which causes the aging process.                  Our hypothesis is that apple juice will
Animals can produce their own amount             turn into a blue suspension first, so the
of vitamin C, all animals but chimps,            grapefruit juice contains the most
guinea pigs and human beings.                    vitamin C.
Since the time of the hunter-gatherer,           This is based on the theory of S.K. Lee
people started to eat fruits and eatable         and A.A. Kader that says, that the
plants. These fruits consist of vitamin C        temperature of the place where the
and today it’s still recommended to eat          fruit grows has influence on the
two pieces of fruit to maintain the level        amount of vitamin C found in this fruit.
of vitamin C in your body.
The molecular formula of vitamin C is            Experimental procedure and
C6H8O6 (see figure 1).                           approach
                                                 To start, begin with cleaning everything
                                                 with distilled water. When everything is
                                                 thoroughly clean, fill the burette with
                                                 KIO3(aq) (0,0050M) . After this, fill the
                                                 pipette of 25 mL with apple juice. The
                                                 apple juice consisted extra vitamin C
                                                 as seen on the packing. When the
                                                 pipette is filled with 25 mL of apple
                                                 juice, put it in the erlenmeyer. Also add
                                                 a bit of starch- solution (C6H10O5)n
Figure 1: structure of vitamin C
(aq)) and sulphuric acid (H2SO4 (aq)).       Apple juice            KIO3-(aq)
Then fill another pipette, this time one     mixture                (mL)
of 10 mL, with a solution of KI and add      (mL)
this too, to the erlenmeyer. Now the         25,00                  3,40
titration can begin. Carefully the KIO3      25,00                  3,30
(aq) of the burette is dripped in to the     Average: 25,00         3,35
erlenmeyer until there is a changing of      Table 1: the results of the KIO3-(aq) (mL)
color to blue/black. This change of          in the two titrations of 25.00 mL Apple
color is caused when the vitamin C has       juice mixture.
reacted with I2 (aq) (see reaction 2)
and the starch comes in touch with the       Grapefruit juice      KIO3-(aq)
I2. This I2 arises when the reaction         mixture               (mL)
between IO3- (aq) and I- (aq) has taken      (mL)
place (see reaction 1).                      25,00                 4,33
                                             25,00                 4,11
-Reaction 1                                  Average: 25,00        4,22
IO3- (aq) + 5I- (aq) +6H+ (aq)  3I2 (aq)    Table 2: the results of the KIO3-(aq)
+ 3H2O(l)                                    (mL) in the two titrations of 25,00 mL
                                             Grapefruit juice mixture.
-Reaction 2
C6H8O6 (aq) + I2 (aq)  C6H6O6 (aq) +        Data analysis
2H+ (aq) + 2I-(aq)                           The 25,00 mL solutions of the apple
                                             juice mixture and the grapefruit juice
Repeat the same experiment with              mixture were titrated with 0,0050 mol/L
grapefruit juice.                            KIO3-(aq).
                                             To start with apple juice, table 1 shows
                                             that an average of 3,35 mL is
                                             necessary for a color change. So the
                                             calculations with the average amounts
                                             conclude: 3,35 mL x 0,0050 mmol/mL
                                             = 0,01675 mmol C6H8O6. Because IO3-
                                             and I2 react in a ratio of 1:3 and
                                             C6H8O6 and I2 in a ratio of 1:1.
                                             C6H8O6 has a molecular weight of
                                             176,13 g/mol so in 25 mL of apple juice
Figure 2: experimental set-up
                                             there are 0,01675 x 176,13 = 2,95 mg
                                             C6H8O6. In 100 mL there are 2,95 x 4 =
                                             11,8 mg C6H8O6.
During the titration of the KIO3- solution
with the apple juice mixture the
                                             The grapefruit juice, as shown in table
indicator changed color from goldish
                                             2, has an average of 4,22 mL, which is
yellow to black/dark blue. Table 1
                                             needed for a color change.
shows the results of the two
                                             4,22 mL x 0,0050 mmol/mL = 0,0211
measurements with apple juice. Table
                                             mmol C6H8O6.
2 shows de results of the two
                                             25 mL of grapefruit juice has 0,0211 x
measurements with grapefruit juice.
                                             176,13 = 3,72 mg of C6H8O6. In 100
When the grapefruit juice was the
                                             mL there are 3,72 x 4 = 14,9 mg
same blue color as the apple juice after
the titration, the titration of grapefruit
juice was finished.
                                            with more pieces of different fruit from
                                            different countries.

                                            There might be slight errors in the
                                            measurements, because the
                                            experiment is done by hand and this
                                            means that there is an inaccuracy.
                                            It is also hard to decide which color of
                                            dark blue is the right one. So it’s hard
                                            to say when all the vitamin C has
                                            reacted with the I2.
Figure 3: the calibration curve.            To have a good experiment there is
                                            need of more kinds of juices, so the
In de calibration curve, you can see        apple juices could be compared to
different amounts of vitamin C and the      each other and a few grapefruit juices
need of KIO3-(aq) to turn the solution      to each other, before comparing the
into blue/black.                            apple juice with the grapefruit juice,
This calibration curve is obtained from     because there might be a lot of
an experiment that the teacher has          differences between two kinds of apple
done. This curve has nothing to do with     juices. But still the hypothesis was right
our own experiment, but indicates the       and the experimental question is
regular reaction between C6H8O6 and         answered. So, grapefruit juice contains
                                            the biggest amount of vitamin C.
Conclusion and discussion
                                            Mixture     Moles      Milligrams
As shown in the calculations there is a
                                            (mL)        C6H8O6     C6H8O6 in
bigger amount of vitamin C in
                                                        in 25,00   100 mL
grapefruit juice than in apple juice.
The measurements of the calibration
                                            Apple       0,01675   11,80071
curve have been measured only once.
The reason for this is a shortage of
                                            Grapefruit 0,0211 14,865372
In table 3, the results of the titrations
can be found. Here you can see that         Table 3: Moles of C6H8O6 in 25,00 mL
                                            and milligrams C6H8O6 in 100 mL in apple-
there is much more C6H8O6 in                and grapefruit juice.
grapefruit juice than in apple juice.
These results support the hypothesis in     It is well known that grapefruit contains
the affirmative. It also supports the       more vitamin C than apple, so that is
theory of S.K. Lee and A.A. Kader.          why the grapefruit juice also contains
The theory says that fruits that grow in    more than the apple juice.
higher temperatures contain more            It would be more relevant to find out in
vitamin C and the experiment confirms       another experiment how much the
this, because grapefruits grow in a         amount of vitamin C decreases when a
warmer climate than apples.                 fruit is made into a juice.
Of course two pieces of fruit aren’t        What’s more, how much vitamin C
enough to conclude that the theory of       disappears when a fruit is fabricated
S.K. Lee and A.A. Kader is right.           into a juice? And contains fresh juice
If we want to prove that that theory is     more vitamin C than fabricated vitamin
right we have to do this experiment         C?
Bibliography                                horticultural crops: S.K. Lee, A.A.
1.                                          Kader      5. Buil, S. ir., (2009). Explanation and
2.                                          stencils. The Hague: Gymnasium     Haganum
3.   6. Verkerk, G. dr., (a.o.) (2004). Binas,
4. Preharvest and postharvest factors       table 82A, Groningen: Wolters
influencing vitamin C content of            Noordhoff.