Tuesday 14 May 2013

09:05 - 1 comment

Experiment 4: Experiment on Vitamin C


GUIDE 4: EXPERIMENT ON VITAMIN C

Introduction
We will measure the amount of vitamin C in many different types of foods. The chemical reaction we will use to measure the amount of vitamin C uses one of its functions in the body. Vitamin C involves in our cells oxidation-reduction reactions. Vitamin C can react with iodine. Therefore we will measure the amount of vitamin C by adding iodine to our food extracts until the vitamin C can bind no more iodine. Iodine in excess of the vitamin C will react with a starch solution you will add to the extract to produce a bluish-black color. The addition of a chemical to measure another chemical is called a titration.

1.             Measuring Vitamin C using starch-iodine test.
Materials
1.      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)
2.      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).
3.      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.
4.      Hydrochloric Acid (HCl) 1 M, (5 ml)
5.      Blender
6.       Filter/ cheesecloth

Procedure

1.        Preparing the vitamin C extracts:
i. Chop food material into small pieces and place into blender.
ii. Add 100 ml of distilled water to the blender.
iii. Blend using the highest speed until the material is thoroughly ground.
iv. Strain the ground extract
v. Measure 30 ml of the strained extract into a 250 ml Erlenmeyer flask or beaker.
2.    Measuring vitamin C in the food sample:
i. Place 30 mL of the food extracts solution in a 250 ml flaskor beaker.
ii. Add 2 drops of the 0.1 M HCl to the flask.
iii. Add 5 ml of the starch solution to the flask.
iv. Fill a burette with the iodine solution.
v. Record the initial volume reading.
vi. Add the iodine solution in 1 ml increments to the flask while swirling the flask.
vii. Add iodine until the solution stays blue-black for 15 seconds.
viii. Record the volume reading on the burette.

3.    Comparing cooked food and raw food’s vitamin C
Does the way you prepare your food affect the vitamin C available to be ingested? Vitamin C is a water-soluble vitamin. Would cooking food by boiling in water affect the vitamin C content? If vitamin C is lost during the cooking process, where does it go? What types of experiments could you design to test your hypothesis? You will be testing your hypothesis to determine if vitamin C content is changed during cooking or if different ways of food preparation yield different amounts of vitamin C.

i. Food can be prepared according to your creativity. For example, you can boil or steam or place in a freezer. You can also prepare the food by different exposing time to heat etc.
ii. Chop food material into small pieces and place into blender.
iii. Obtain your data using the same method in previous section.
iv. Record the volume reading on the burette.
v. Compare the relative amounts of ascorbic acid present in the samples you are testing.
vi. Compare your results with those of other members of the class. What do the results show?

2.      Application: Magic Writing

Materials
Beaker
Iodine
Lemon/Lime juice
Notebook paper
Cup
Art brush

Procedure:
STEP A: IODINE SOLUTION
1. Pour 100 ml water into a 500ml-beaker.
2. Add 10 ml of Iodine to the water and stir.

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

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

STEP D:
1. Dip the art brush into the lemon/lime juice
2. Write a message on the piece of paper.
3. Allow the juice to dry on the paper.
4. Submerse the paper in the iodine solution in the bowl.


 Result

PART: 1. Measuring Vitamin C using starch-iodine test.


Table 1

Sample: Broccoli
Ascorbic acid:
[1 mg/ml = 75.3 ml Iodine]


Condition
(Broccoli)

Reading I
(ml)

Reading II
(ml)
Average Vitamin C concentration in    30 g (mg/ml)
Vitamin C concentration in       100 g (mg/ml)
Fresh
48.9
41.2
0.60
2.00
Water Bath
(60 °C)
46.5
40.4
0.58
1.93
Boil
(150 °C)
38.7
33.4
0.48
1.60


Calculation:

Fresh Broccoli

Reading I = (1 mg/ml ÷ 75.3 ml) x 48.9 ml = 0.65 mg/ml
Reading II = (1 mg/ml ÷ 75.3 ml) x 41.2 ml = 0.55 mg/ml
Average vitamin C  in 30g = 0.60 mg/ml
Vitamin C in 100g = (0.60 mg/ml ÷ 30g) x 100 = 2 mg/ml
                       
Water Bath(60 oC)

Reading I = (1 mg/ml ÷ 75.3 ml) x 46.5 ml = 0.62 mg/ml
Reading II = (1 mg/ml ÷ 75.3 ml) x 40.4 ml = 0.54 mg/ml
Average vitamin C  in 30g = 0.58 mg/ml
Vitamin C in 100g = (0.58 mg/ml ÷ 30g) x 100 = 1.93 mg/ml

Boil 150oC(hot plate)

Reading I = (1 mg/ml ÷ 75.3 ml) x 38.7 ml = 0.51 mg/ml
Reading II = (1 mg/ml ÷ 75.3 ml) x 33.4 ml = 0.44 mg/ml
Average vitamin C  in 30g = 0.48 mg/ml
Vitamin C in 100g = (0.48 mg/ml ÷ 30g) x 100 = 1.60 mg/ml


PART: 2. Application: Magic Writing

The paper turns a blue-puple except where the message was written. The words are outlined by the dark background. This is due to the starch combines with the iodine forming iodine-starch molecules. These molecules are blue-purple in color. Vitamin C combines with iodine to form a colorless molecule. The area covered with lemon juice remains unchanged because the paper is coated with vitamin C from the lemon.

Discussion

Broccoli is a plant in the cabbage family, whose large flower head is used as a vegetable. Broccoli is high in vitamin C and dietary fiber. It also contains multiple nutrients with potent anti-cancer properties. 

Vitamin C is an organic molecule known as ascorbic acid. Vitamin C is a water-soluble vitamin that occurs naturally in many fruits and vegetables. It can be found in oranges, limes, lemons,  cabbage, strawberries, tomatoes, spinach, other leafy vegetables, or other citrus fruits. The indicator  was added to the sample, and the indicator will produce a dark blue color when the endpoint has been reached. The amount of iodine added from the burret will be an indication of the amount of vitamin C. Vitamin C is a sensitive molecule that is altered in the presence of heat.  It is not stable to heat, so cooking fruits and vegetables destroys much of their vitamin C content.

From the Table 1, fresh broccoli contains a high concentration of vitamin C which is 17.9 mg/ml. The lowest concentration of vitamin C is boil Broccoli at 150°C with vitamin C concentration is 14.37mg/ml. Heat decreases the vitamin C level. Vitamin C is damaged by heat by increasing its rate of oxidation.

The heat actually preserves vitamin C if the temperature is below 70 degrees Celsius, because the high heat used kills the enzyme ascorbic acid oxidase, found in fruits and vegetables, before much Vitamin C is oxidized. Since this enzyme catalyzes the oxidation process, this is actually serve to protect the vitamin. However, if the temperature rises above 70 degrees Celsius, then the vitamin C will be damaged.

Conclusion

Fresh Broccoli has the highest concentration of Vitamin C which is 17.9mg/ml. The lowest concentration of vitamin C is boil Broccoli at 150oC which is 14.37mg/ml.







1 comments:

Thanks for sharing the necessary information. Enhance vitamin D through vitamin d tablets

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