Project 3: Measuring Vitamin C

INTRODUCTION

There are many foods that are containing vitamin C  such as fruits, drinks and vegetables. Vitamin C, more properly calledby ascorbic acid, is an essential antioxidant needed by the human body. In this experiment, we are going to measure the amount of vitamin C by using the given formula in manual. Different foods have differ amount of vitamin C, so in this experiment, we can know from different food sample, the roughly amount vitamin C on it. As the iodine is added during  titration, the ascorbic acid is oxidised to dehydroascorbic acid, while the iodine is reduced to iodide ions.

Due to this reaction, the iodine formed  immediately reduced to iodide as long as there is any ascorbic acid present. Once all the ascorbic acid has been oxidised, the excess iodine start to react with the starch and then forming the blue-black starch-iodine complex. This is the endpoint of the titration.

MATERIALS

1. Vitamin C standard (0.2 mg/ml)
2. Food sources of vitamin C: for example juices, extraction of plants, flowers, fruits, grains, and vegetables, vitamin C tablet or cooked/treated food sample (boiled/refrigerated/grilled)
3. Starch solution (1%): Mix 1 g starch in 100 ml boiling H2O. Boil for one minute while stirring. Stir until completely dissolved (this solution will be cloudy).
4. Iodine solution: Mix 0.6 g potassium iodide in 500 ml H2O. Mix 0.6 g iodine in 50 ml of ethyl alcohol. These two iodine solutions should be mixed well before combining. Combine the two iodine solutions and add an additional 450 ml of H2O.
5. Hydrochloric Acid (HCl) 1 M, (5 ml).
6. Blender.
7. Filter/ cheesecloth.

PROCEDURE

1. Preparing the vitamin C extracts:
i. Food material was chopped into small pieces and was placed into blender.
ii. 100 ml of distilled water was added to the blender.
iii. Blend was used the highest speed until the material is thoroughly ground.
iv. The ground extract was strained.
v. 30 ml of the strained extract was measured into a 250 ml Erlenmeyer flask or beaker.

2. Measuring vitamin C in the standard and food sample:
i. 30 mL of the Vitamin C Standard was placed in a 250 ml flask or beaker.
ii. 2 drops of the 0.1 M HCl was added to the flask.
iii. 5 ml of the starch solution was added to the flask.
iv. A burette was filled with the iodine solution.
v. The initial volume reading was recorded.
vi. The iodine solution in 1 ml increments was added to the flask while swirling the flask.
vii. Iodine was added until the solution stays blue-black for 15 seconds.
viii. The volume reading on the burette was recorded.
ix. Step i to viii was repeated to measure the vitamin C in the food sample.
x. The amount of Vitamin C in the food sample was calculated using this formula:



3. Comparing cooked food and raw food’s vitamin C
i. Food was prepared according to our creativity. For example, boil or steam or place in a freezer.
ii. Food material was chopped into small pieces and was placed into blender.
iii. Data was obtained using the same method in previous section.
iv. The volume reading on the burette was recorded.
v. The relative amounts of ascorbic acid present in the samples testing was compared.
vi. Our results with those of other members of the class was compared. 

Application: Magic Writing

MATERIALS

Beaker
Iodine
Lemon/Lime juice
Notebook paper
Cup
Art brush

PROCEDURE

STEP A: IODINE SOLUTION
1. 100 ml water was poured into a 500ml-beaker.
2. 10 ml of Iodine was added to the water and stir.

STEP B:
1. A section from the notebook paper was cut.
2. The paper must fit inside a 500ml-beaker.

STEP C: VITAMIN C SOLUTION
1. The juice of the lemon/lime was squeezed into another beaker.

STEP D:
1. The art brush was dipped into the lemon/lime juice
2. A message was writed on the piece of paper.
3. The juice was allowed to dry on the paper.
4. The paper was submersed in the iodine solution in the bowl.

RESULT

Standard Vitamin C

Volume of iodine used
Average
I
II
( 15 + 15.3 ) mL
15 mL
15.3 mL
2
= 15.2 mL


Food Sample
Volume of iodine used, mL
Amount of vitamin C in
15 g food sample
Vitamin C in 100 g
food sample
Raw
Treated
Raw
Treated
Raw
Treated
Iced lemon tea
5.6
3.5
0.074
0.047
0.493
0.313
Rice
4.5
4.0
0.059
0.053
0.393
0.353
Broccoli
19.0
11.5
0.250
0.150
1.667
1.000
Papaya
18.0
17.3
0.240
0.230
1.600
1.533
Orange
15.0
14.1
0.197
0.186
1.313
1.240
Flower
9.00
6.00
0.118
0.079
0.787
0.527

Magic Writing


DISCUSSION

In this experiment we perform an oxidation-reduction titration. We mixed vitamin C with the starch, and gradually titrated it using iodine. Iodine reacted with vitamin C and did not reacted with the starch. However, after the vitamin C (ascorbic acid) had been fully reacted with iodine, iodine will reacted with starch producing blue-black colour in the solution. The blue-black colour indicates the amount of iodine needed to react with vitamin C. 

Based on our result, we obtain that the highest amount of vitamin C in our food sample is broccoli, followed by papaya, orange, flower, iced lemon tea and lastly rice. this food sample is also treated to see if there any changes when titrating them with iodine.

Surprisingly, there are changes in the amount of iodine used to react with the vitamin C. The amount of iodine used was decreased in treated vitamin C. This mean that, treated vitamin C produce less vitamin C. In magic writing, we wrote our name using lemon juice, and soak it in iodine solution.

CONCLUSION

In conclusion, we can conclude that broccoli have higher amount of vitamin C compare to other food sample. After that, we can say that, cooking or keeping food in refrigerator can reduce the amount of vitamin C in food. Lastly, this experiment proof that treated vitamin C will resulting in less vitamin C. 

QUESTIONS

1. What juices or drinks had the most vitamin C?
Citric juices have most highest vitamin C

2. Did the drinks have the vitamin C that they advertised on the labels?
The drinks show zero amount vitamin C but we detect a little amount vitamin C in our experiment

3. What food sources had the most vitamin C?
Red peppers

4. What families or groups had the most vitamin C?
Citrus families.

5. Did plants that you do not normally eat have vitamin C?
Yes, vegetables. Some vegetables have a lot of vitamin C.

6. Did heat affect the vitamin C content of food?
Yes.

7. Did heat increase or decrease the vitamin C levels?
Decrease vitamin C levels.

8. What way of food preparation would be the most nutritious ?
Steaming cooking.

9. Do you have any ideas now to get more vitamins from your meals?
Yes. I need to eat more fruits and vegetables to get more vitamin C.

REFERENCES

1. A Text Book of Biochemistry for Medical Students, 9th ed. New Delhi : UBS Publisher’s Distributors Ltd., 2003
2. R. K. Murry, D. K. Granner, P.A. Mayes, V. W. Rodwell, Harper’s Biochemistry, Prentice Hall International Inc., Latest Edition.
3. https://studymoose.com/%EF%BB%BFeffect-of-temperature-on-content-of-vitamin-c-essay