1. Vitamin C Concentration in Organic Broccoli compared to Conventional Broccoli
Acknowledgments
We
would
like
to
say
a
special
thanks
to
Jenn Halpin,
the
Dickinson
College
Farm,
Youki Sato
and
Professor
St.
Angelo.
Alex
Medeiros
and
Carlin
Smith
Chemistry
Dickinson
College
Introduction
Vitamin C is an essential nutrient which means that it is necessary for human
health and it cannot be synthesized by humans. It is used to maintain intercellular
connective tissues and collagen as it is an electron donor.1 It is also integral for the
synthesis and regulation of a number of important chemicals in humans including
dopamine.2
This project examines the vitamin C content in broccoli because it is a
common vegetable and is high in vitamin C compared to other produce available
from the College Farm. The use of broccoli makes it meaningful because the
results of our experiment can help to determine how much of each type of broccoli
is needed to fulfill the recommended daily intake of vitamin C. For this experiment,
the concentrations of ascorbic acid in Dickinson College Farm organic broccoli will
be compared with conventionally farmed broccoli.
It was hypothesized that the college farm broccoli would be higher in vitamin C
than the conventionally farmed broccoli. A High Pressure Liquid Chromatography
(HPLC) assay and a titration using 2,6-­Dichlorophenol Indophenol (DCPIP) was
conducted to determine the concentration of vitamin C in each type of broccoli.
References
1. Padayatty,
S.
J.;
Levine,
M.
Canadian
Medical
Association
Journal 2001,
164 (3),
353–
355.
2. Agarwal,
A.;
Shaharyar,
A.;
Kumar,
A.;
Bhat,
M.
S.;
Mishra,
M.
Journal
of
Clinical
Orthopaedics and
Trauma 2015,
6 (2),
101–107
Methods
HPLC
Samples of each type of broccoli were separately pureed in a blender with
water in a 1:1 mass ratio. The broccoli solution was then centrifuged for five
minutes and then vacuum filtered in order to make it easier to remove the
supernatant. The solution was then diluted to 10% and 5%. HPLC tests were run
for the 100%, 10%, and 5% concentrations along with four different standard
solutions of ascorbate.
We used the HPLC values of the ascorbate standards to create a curve and
equation of best fit. Using this equation we were able to calculate the concentration
of ascorbic acid in the samples. We converted this to the concentration of
ascorbate in the test solution by multiplying the concentration of each sample by
the dilution factor.
y=1.4388x + 23.523
Titration
Samples of each type of broccoli were separately pureed in a blender with
water in a 1:2 mass ratio. The broccoli was then vacuum filtered. A 0.1% solution
of DCPIP was made and was used to fill the burette. Each type of broccoli was
then titrated three times and the change in titrant volume was recorded in liters.
The following formula was used to calculate the number of mg of ascorbic acid in
100 grams of broccoli.
Conclusion
According to the results of the HPLC assay, the organic broccoli has 1.90 times
the concentration of ascorbic acid than conventional broccoli does. The results of
the Titration confirm this, as the results show that organic broccoli has 1.75 times
the concentration of ascorbic acid than conventional broccoli does. It should be
noted that the values calculated for the titration are off by a factor of 10. However,
the results are still relevant and can be used to compare the values.
After completing the experiment and reviewing the data, there are changes that
should be made to the methods. During filtration some of the ascorbic acid was
filtered out. A larger amount of water, a better blender, and a different filtration
method could be used to reduce the amount of ascorbic acid lost. The titration
results were not very accurate as the concentration of DCPIP was too high to
notice small changes in the color of the titrant. A smaller concentration such as
0.01% may allow for a more accurate measurement to be made.
Results
Broccoli Type % Broccoli
Concentration
mg of Ascorbic
Acid per 100 g
Broccoli
Average mg of
Ascorbic Acid per
100g Broc.
Organic 100 88.35 94.85±9.82
Organic 10 87.46
Organic 5 108.73
Conventional 100 41.04 49.41±10.49
Conventional 10 42.99
Conventional 5 64.20
Table 1. Milligrams of Ascorbic Acid per 100 Grams of Broccoli Found Using HPLC
Broccoli Type Trial # Change in Vol. (L) mg of Ascorbic Acid
per 100 g Broccoli
Average mg of
Ascorbic Acid
per 100g Broc.
Organic 1 0.00045 9.51 7.40±1.49
Organic 2 0.00030 6.34
Organic 3 0.00030 6.34
Conventional 1 0.00015 3.17 4.23±0.86
Conventional 2 0.00020 4.23
Conventional 3 0.00025 5.28
Table 2. Milligrams of Ascorbic Acid per 100 Grams of Broccoli Found Using Titration