Vitamin C, an ascorbic acid, is essential to human bodies and is commonly
found in oranges, helping in body tissue repair, healing, and boosting body
immunity. It degrades easily when exposed to environmental conditions heat,
air, becoming dehydroascorbic acid upon degradation, which is useless to the
body. Cut oranges are served at a later time to customers in fruit stalls and
banquets. This poses an issue as during the waiting time, Vitamin C content
in oranges degrades quickly, causing ascorbic acid content in oranges and
vitamin c content taken in by consumers to be lesser. Due to the high chance
that this reduced ascorbic acid concentration taken in is unable to benefit our
body, our group experimented on methods to reduce ascorbic acid loss in
oranges. Through this project, we learned that heat, air affects ascorbic acid
loss the most, indicating that the absence of factors heat, air is most effective
in reducing ascorbic acid degradation in oranges.
The purpose of this experiment is to find out what are some
ways to preserve Vitamin C in cut oranges by slowing down
it’s rate of degradation in cut oranges. Our literature review
suggests that refrigeration, reduced exposure to air and
moisture helps to reduce Vitamin C loss in cut oranges.
Hence, we have decided to find out out among the 3
methods, which is the most effective. A combination of the 3
methods will also be used to further experiment on the most
efficient way to preserve Vitamin C.
Based on the theory that ascorbic acid degrades over time more
quickly due to the presence of light, heat and air, we felt that the
presence of heat and air strongly affects ascorbic acid degradation.
Hence, we decided to test on these two major factors in our
experiment.
The experiment is to find out the efficiency of ascorbic acid
preservation methods, in cut oranges, we will focus on factors
regarding heat, air. Our literature review shows refrigeration, reduced
exposure to air 2, lowers Vitamin C loss in cut oranges. So, we seek
ways to preserve Vitamin C by conducting investigations using titration,
stoichiometric ratio calculations to determine Vitamin C level in
oranges pre, post-preservation. The results of titration method were
inaccurate in showing the ascorbic acid degradation as the endpoint
was subjective. Thus, we used the High-Performance Liquid
Chromatography(HPLC) method, where the accuracy is much higher
than titration, allowing the obtaining of more accurate results. In our
early discussions and in the midst of using the titration method, we
decided to include 4 setups: one at room temperature, one cling
wrapped at room temperature, one in the refrigerator and one cling
wrapped in the refrigerator. After the experiment, we felt that our
results were not accurate enough and decided to add 1 more setups
while using the HPLC method: At 40 degrees Celsius in the laboratory
oven, to further investigate the effect of heat on the loss of ascorbic
acid in oranges.
[1]Cut the orange into halves , put one half in a respective
preservation condition and
wait for 1 hour. The preservation conditions are:
A. Normal – left alone in room temperature. (Control)
B. Left in Fridge
C. Cling wrapped in room temperature
D. Cling wrapped and in fridge
The other half, test immediately using the following steps
[2]Remove the skin.
[3]Weigh the flesh of each half and record it.
[4]Crush and collect the juice using
mortar and pestle.
[5]Add distilled water on the flesh and continue
crushing it further on the sieve till it is
100 ml.
[6]Pour 20 ml of orange juice(stir before pouring),
150 ml of distilled water and 1 ml of starch into
a conical flask and titrate the mixture with
0.005 mol/L of iodine solution until it
turns into the desired blue black. Record
readings once titration is completed.
[7]Repeat step 6 for 4 more times.
[8]Repeat steps 2 to step 7 for the other half after 1 hour in
respective preservation conditions.
[9] Calculate the concentration of vitamin-C as follows
Based on the equation:
Ascorbic acid + I2
2I + dehydroascorbic acid
1: 1 stoichiometric reaction
1V1 = 1
M2V2
1
Molarity of vitamin C = 0.005 x volume of iodine used
20
Molarity obtained was divided by mass of skinned orange
half
to obtain Molarity per gram of orange.
Method
of
Ascorbic
acid method
Percent
The
percentage
loss ofacid
VitaminAscorbic
C for each
isdrop
preservation
concentration
concentration
(%)
measured, based on the formula
After
Initial amount ofBefore
Vitamin C – Final
amount of Vitamin C x
preservation /
preservation /
100%
molarity per
molarity per
Initial amountgram
of Vitamin
C
gram of orange
of orange
E.g. 0.005*7.775/20/62.71=0.0000309959(before
preservation)[Initial
amount]
Control
3.595×10^(-5)
3.349×10^(-5)
6.84
0.005*8.45/20/68.71=0.0000307451(after
Fridge
3.375×10^(-5)
4.186×10^(-5)
22.12
preservation)[Final
amount]
Cling wrapped
4.793×10^(-5)
4.688×10^(-5)
2.19
((0.0000309959-0.0000307451)/0.0000309959)*100=0.79%
Cling wrapped
and fridge
3.100×10^(-5)
3.075×10^(-5)
0.80
___________________________________________________________
If we were to conduct this experiment again, we would
1.
Do every preservation method on the same day to prevent
inconsistency
2.
Make more time readings instead of 1 hour intervals.
3.
Make sure room temperature is constant.
4.
Repeat each method several times to prevent biased results.
5.
Complete the experiment quickly, as iodine and starch titration
decolourises after some time.
6.
Make sure the blue-black end point is permanent, as it faded away in
some of the flasks after a while, possibly causing inaccuracies.